Addis Ababa University School of Graduate Studies Institute of Technology Department of Chemical Engineering

ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES INSTITUTE OF TECHNOLOGY DEPARTMENT OF CHEMICAL ENGINEERING

EFFECT OF PROCESSING ON SOME QUALITY ATTRIBUTES OF MANGO (Mangifera indica) FRUIT LEATHER

By BINYAM TESHOME

A Thesis submitted to the school of Graduate Studies of Addis Ababa University in partial fulfillment of the Requirements for the Degree of Master of Science in Chemical Engineering (Food Engineering)

Advisor: Mr. Adamu Zegeye

May, 2010 Addis Ababa Ethiopia ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES INSTITUTE OF TECHNOLOGY DEPARTMENT OF CHEMICAL ENGINEERING

EFFECT OF PROCESSING ON SOME QUALITY ATTRIBUTES OF MANGO (Mangifera indica) FRUIT LEATHER

By Binyam Teshome

Approved by the Examining Board:

______Chairman, Department’s Graduate Committee

Mr. Adamu Zegeye ______Advisor

Dr. Cherinet Abuye ______External Examiner

Dr. Eng. Shimelis Admassu ______Internal Examiner

Acknowledgment

I would like to forward my deepest gratitude to my advisor Mr. Adamu Zegeye for his keen interest in my thesis work, follow up of my progress, encouragement and support.

I acknowledge Addis Ababa Institute of Technology for the financial support. I am also grateful to the academic staff of the Department of Chemical Engineering for imparting tremendous knowledge to me. I appreciate Dr. Eng. Shimelis Admassu for his constant supervision and recommendation during my project work. Thanks to the Ethiopian Health and Nutrition Research Institute (EHNRI) for letting me use their food analysis laboratory and facilitating my research, especially Dr. Cherinet, Ato Adamu and Israel. Ethiopian Et-Fruit Company is also appreciated for providing the mango varieties used in this research. I thank all the technical staff of my Department’s laboratory, particularly, Ato Hintsasilase Seifu and also Yeshihareg Nesibu for providing me all the necessary support during the research.

Equally and importantly, I would like to acknowledge all family members particularly Girum Teshome and my dearest wife Hayley Teshome, who contributed towards my success with their financial support and encouragement in the course of this research, and also honor my friends who shared my idea when I was in need.

Table of Contents

CHAPTER Title Page

Title Page i Acknowledgment ii Table of Contents iii List of Tables vi List of Figures viii List of Abbreviations ix Abstract x

1 INTRODUCTION 1 1.1. Background 1 1.2. Statement of the problem 3 1.3. Objectives 4 1.4. Structure of the thesis 5 2 LITERATURE REVIEW 6 2.1. Production and marketing of Mango fruits in Ethiopia 6 2.1.1 Exporting Mango fruits 7 2.1.2 Mango value chain analysis in Ethiopia 8 2.1.3 Asossa market 9 2.1.4 Addis Ababa market 9 2.2 Processing of Mango fruits in Ethiopia 12 2.3 Selected Mango varieties for processing 13 2.4 Medicinal uses and by-products of Mango 14 2.5 Mango processing technologies 14 2.5.1 Ripe Mango processing 16 2.6 Fruit leather processing 17 2.6.1 Preparation of fruits 17 2.6.2 Heating, drying and packaging 18 2.7 Mango fruit leather recipes and processing procedures 19

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2.7.1 Adding sweeteners and flavoring to fruit leather 20 2.8 Quality control 20

2.9 Effect of processing on food quality attributes 22 2.9.1 Physicochemical properties 23 2.9.2 Changes on Vitamins 24 2.9.3 Flavor and pigment components 26 2.9.4 Sensory attributes 29 2.9.5 Influence of drying process 30 2.10 Food safety 31

3 MATERIALS AND METHODS 32

3.1 Raw material source and equipment 32 3.2 Approach for selection and preparation of Mango fruits 32 3.3 Development of Mango fruit leather 33 3.3.1 Raw material preparation and formulation of the puree mix 33 3.3.2 Heating and drying the puree mix 34 3.4 Methods for studying the effect of processing 37 3.4.1 Effect of processing on drying time 37 3.5 Quality parameters for studying the effect of processing 38 3.5.1 Proximate analysis methods for the puree and leather 38 3.5.2 Physicochemical analysis 41 3.5.3 Texture analysis of the Mango leather 42 3.5.4 Microbiological analysis 43 3.5.5 Sensory evaluation 44 3.6 Experimental design and data analysis 44 4 RESULTS AND DISCUSSION 45 4.1 Physicochemical properties of Mango puree 45 4.2 Proximate analysis results of the Mango puree and puree mix 46 4.2.1 Keitt Mango variety 47 4.2.2 Tommy Atkins Mango variety 47

4.3 Effect of heating temperature on viscosity of Mango puree mix 48 4.3.1 Keitt Mango variety 49 4.3.2 Tommy Atkins Mango variety 50 4.4 pH of the puree mix 51 4.5 Effect of drying on the proximate and Vitamin C content of fruit 51 leather 4.6 Effect of temperature and puree load on drying time 52 4.6.1 Drying characteristics of Mango puree mix 52 4.6.2 Analysis of moisture loss during drying process 53 4.7 Texture analysis of the Mango leather 54 4.8 Proximate analysis of Mango fruit leather 55 4.8.1 Moisture content 56 4.8.2 Protein content 57 4.8.3 Fat content 57 4.8.4 Crude fiber content 58 4.8.5 Ash content 58 4.8.6 Carbohydrate content 59 4.8.7 Effect of processing on Vitamin C content of Mango leather 59

4.9 Microbiological analysis of Mango fruit leather 60 4.10 Sensory analysis of Mango fruit leather 61

4.10.1 Effect of drying temperature, puree load and fruit varieties 61 on the sensory qualities 5 SUGGESTED TYECHNOLOGY FOR MANGO LEATHER 66 PROCESSING 5.1 Process description 66 6 CONCLUSIONS AND RECOMMENDATION 94 6.1 Conclusion 94 6.2 Recommendation 96 REFERENCES 97 ANNEXES 102

List of Tables

Chapter Table Title Page

2 2.1 Estimate of area, production and yield of Mango fruits 6 4 4.1 Physico-chemical properties of fruit pulp for the mango varieties 45 Proximate analysis result for Keitt and Tommy Atkins varieties of 4.2 46 Mango puree and puree mix Results of viscosities for Keitt and Tommy Atkins variety mango 4.3 48 puree mixes measured at different heating temperature 4.4 Proximate analysis result for Mango fruit leathers 51 Designed sample codes for both varieties of mangos with drying 4.5 52 temperature and puree load Effect of drying air temperature and puree load on drying time of 4.6 53 Keitt Mango fruit leather 4.7 Weights and moisture loss of Keitt variety mango leather 53 Results of compression test using Texture Analyzer to different 4.8 54 number of Mango leather sheets (layers) 4.9 Effect of temperature on proximate composition of mango leather 55 4.10 Effect of puree load on proximate composition of mango leather 55 4.11 Effect of fruit variety on proximate composition of mango leather 56 Effect of drying temperature, puree load and fruit variety on 4.12 59 vitamin C content 4.13 Result of microbiological analysis of mango fruit leather 60 4.14 Effect of drying temperature on sensory qualities 61 4.15 Effect of puree load on sensory qualities 61 4.16 Effect of fruit variety on sensory qualities 62 4.17 Proximate and physicochemical composition of Mango and puree 68 4.18 Specific heat relationships for food product components 73 Recipes, calculations and amount of ingredients for making 4.19 85 Mango leather 4.20 Typical losses during processing of fruits and vegetables 86

4.21 Machinery and equipment required for mango leather production 88 4.22 Manpower requirement for Mango leather production 89 4.23 Raw material costs for Mango leather production 89 4.24 Cost of utilities for Mango leather production 90 4.25 Fixed capital cost estimation for Mango leather production 91 4.26 Estimation of total product cost for Mango leather 92

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List of Figures

Page Chapter Figure Title

1 1.1 Structure of the thesis 5 2 2.1 Wholesale Mango market in Addis Ababa – Market share by region 10 3 3.1 Process flowchart for Mango leather processing 36 4 4.1 Viscosity verses temperature of Keitt variety puree mix 49 4.2 Viscosity verses temperature of Tommy Atkins variety puree mix 50 4.3 Qualitative flow diagram for Mango leather processing 67 4.4 Quantitative flow diagram for mango leather processing 78 4.5 Quantitative flow diagram for daily production of mango leather 80 4.6 Equipment layout for mango leather processing 81

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List of Abbreviations

AAU Addis Ababa University

AMARI Awash Melkasa Agricultural Research Institute

AOAC Association of Official Analytical Chemists

BAM Bacteriological Analytical Manual

CIA Central Intelligence Agency

CSA Central Statistical Authority

EHNRI Ethiopian Health and Nutrition Research Institute

ETB Ethiopian Birr

Et-Fruit A state owned Ethiopian Fruit Marketing Agency

FAO Food and Agriculture Organization

FDA Food and Drugs Administration

GTZ Gesellschaft für Technische Zusammenarbeit

LSD List Significance Difference

MC Moisture Content ppm parts per million

RH Relative Humidity

SPSS Statistical Package for Social Scientists

TCA Trichloro Acetic Acid

TSS Total Soluble Solid

UAE United Arab Emirates

USD United States Dollar

USDA United States Drug Administration

Abstract

The seasonal production of mango fruit in Ethiopia has to be considered as an opportunity for the utilization of the fruit. The objective of this research was to study the influence of processing on some quality attributes of mango fruit leather developed from two fruit varieties namely, Keitt (local mango) and Tommy Atkins (export standard mango). First, 3.2 kg of mango fruit from both varieties were allocated for the process to be peeled, cut, sliced into pieces and stones removed. Mango puree was made using a food processor to obtain 1.65 kg puree. It was put in a beaker and covered with aluminum foil and then inserted into a water bath fitted with thermostat to control the temperature. Additional ingredients of Honey, Ginger and Lemon Juice were added and mixed. In order to cook and shorten the drying time, the mixture was heated at three different temperatures, 600C, 700C and 800C whilst being continuously stirred. The puree mixture was poured onto the trays to an approximate thickness of 0.64 cm. The trays containing the puree were placed in a drying oven. Oven drying was conducted for 8 h and finally 0.52 kg of mango leather was obtained. Drying experiment was also undertaken using convective hot air dryer to minimize the drying time of the fruit leather using a similar procedure. A minimum drying time of 4 h was achieved in a convective hot air dryer for Keitt mango fruit leather at 800C with 0.4 g/cm2 puree load. The major factors considered to have an effect on the leather quality were drying temperatures of 600C, 700C and 800C, puree load of 0.4 g/cm2 and 0.6 g/cm2 and fruit variety. The developed leather underwent physico-chemical, textural, microbiological and sensory analysis. The data obtained was analyzed using SPSS version 17 statistical software. The result indicated that 70.3 % of moisture loss resulted in the drying process. The viscosity of the mango puree was found to be dependent on heating temperature. As the temperature increased, the viscosity of the puree first decreased and then increased within the range of temperature 25.1 to 70.0 0C. The texture analysis result of the final mango leather showed that 4 sheets and 5 sheets of leather with 5mm and 6mm thickness, respectively, were found to be suitable for a single bite. The results of the proximate analysis for both varieties of mango fruit leather indicated that the processing affected the nutritional composition of the fruit leather. The vitamin C content was also found to be dependent on all drying temperature, puree load and fruit variety. The vitamin C content of the Keitt mango leather (26.93%) is greater than that of Tommy Atkins mango leather (22.71%). When compared to the fresh puree mix, the Keitt mango leather is decreased by 39.66% and that of the Tommy Atkins mango leather is decreased by 57.82%. The result of microbiological analysis for yeast, coliform, x

fecal coliform, E.coli, and Shigella species was found to be safe (<1X104) and S.coccus and Salmonella species were not isolated for both varieties of mango leathers processed at 600C and 0.6 g/cm2 puree load. The Tommy Atkins mango leathers dried at 60 and 700C with 0.4 and 0.6 g/cm2 puree loads were preferred by panelists (P<0.05). The project generally covered the process and analysis of mango fruit leather and its development at a laboratory scale. Accordingly, an economically feasible production technology has been suggested.

Key words: Leather, Mango, Processing, Quality

CHAPTER 1

INTRODUCTION

1.1 Background

Mango (Mangifera indica L) is a highly seasonal tropical fruit, very popular among millions of people in the tropics. It also occupies a prominent place among the best fruits of the world. However, it is in constant demand, there is a pre-harvest scarcity and at times a post-harvest glut for this fruit. To increase the availability of this fruit throughout the year, the surplus production must be processed into a variety of value-added products (Saxena and Arora, 1997; Srinivasan et al., 2000; Singh et al., 2005). Dried mango products could successfully serve this purpose.

Mangos can be processed into a number of unique products such as dried mango pieces, chutney and mango leathers (Azeredo, et al., 2006). Processing of mangos enables exporters to serve their markets even during ‘off season’ periods for fresh fruits. Mangos are a highly nutritious fruits containing carbohydrates, proteins, fats, minerals, and vitamins, in particular vitamin A (beta

carotene), vitamin B1, vitamin B2, and vitamin C (ascorbic acid). As the fruit ripens, concentrations of vitamin C decrease and glucose, fructose, and sucrose concentrations increase (Bally, 2006).

Drying of agricultural products is the oldest and widely used preservation method. It involves reduction as much water as possible from foods to arrest enzyme and microbial activities hence stopping deterioration. Moisture left in the dried foods varies between 2-30% depending on the type of food. In tropical countries, solar dryers can be used to dry fresh produce when average relative humidity is below 50% during drying period. Drying lowers weights and volume of the product hence lowers costs in transportation and storage. However, drying allows some lowering in nutritional value of the product e.g. loss of vitamin C, and changes of color and appearance that might not be desirable (GTZ, 2009).

Fruit leathers are dried sheets of fruit pulp which have a soft, rubbery texture and a sweet taste. They can be made from most fruits, although mango, apricot, banana and tamarind leathers are amongst the most popular. Leathers can also be made from a mixture of fruits. Fruit leathers are made by drying a very thin layer of fruit puree and other ingredients to produce a leathery sheet of dried fruit with a texture similar to soft leather (Andress & Harrison, 1999). They may be eaten as snack foods as a healthy alternative to boiled sweets and also used as ingredients in the

1 manufacture of cookies, cakes and ice cream. Fruit leathers are often targeted at the health food market, using marketing images such as ‘‘pure”, ‘‘sun dried”, and ‘‘rich in vitamins”.

Mango leather is a traditional product prepared from sound ripe mango. Traditionally, sun drying is the process employed for preparing mango leather from ripe fruit pulp. However the sun-dried product is discolored and the process is unhygienic and lengthy. Cabinet drying has been carried out for making mango leather (Heikal et al., 1972; Mir and Nath, 1995) resulting into a product with improved color and flavor.

The preservation of fruit leathers depends on their low moisture content (15-25%), the natural acidity of the fruit and the high sugar content. When properly dried and packaged, fruit leathers have a shelf life of up to 9 months (FPT, 2009). Although fruit leather is a relatively well established product overseas, few studies have been published about this kind of product. Most of the studies utilize not only fruit purees in the fruit leather, but also other ingredients (especially sugars) and additives. For instance, Chan and Cavaletto (1978) prepared papaya leathers with sucrose and SO2. They observed that SO2 reduced changes in the colour of papaya leathers during both processing and storage. Che Man, et al., (1992) prepared sapota leathers from sapota puree, sucrose, rice flour, sorbic acid, and sodium metabisulphite; the leathers were shelf-stable for 3 months. Jackfruit leathers with added sucrose and sorbic acid were produced by Che Man and Taufik (1995); the product remained stable for 2 months. Irwandi, et al., (1998) produced 12-week stable durian leathers from a formulation including sucrose and sorbic acid. Vijayanand, et al., (2000) produced 3-month shelf-stable guava leathers with sucrose and metabisulphite. Mango leather products have very low protein content (1–2%). Therefore several studies have increased protein content in the mango leather by adding shrimp flour and rice flour, whey protein isolate and soy protein isolate (Exama & Lacroix, 1989; Payumo, et al., 1981; Chauhan, et al., 1998). All the above-mentioned studies reported good consumer acceptance of the fruit leather product.

1.2 Statement of the problem

Mango puree and leather products are largely unknown in Ethiopia, but may have good potential for a number of reasons. According to Kadir (2009) the current postharvest loss of mango fruits in Ethiopia is more than 26.3%. However, there is a growing international demand for dried mango fruits and mango fruit leathers. Consequently the abundant supply of mango fruit in Ethiopia could be utilized to create new products (including organic fruit leathers) for this overseas market.

The expansion of the bakery industry has created a demand for new ingredients, for cake production, which are imported and are relatively expensive. Mango fruit leather, produced locally, could be utilized as a cheaper alternative ingredient. There is also a growing consciousness over the negative effects of sugar confectionery on dental health and at present there are few alternatives for concerned parents to give to their children. Therefore, fruit leather products would be a more acceptable healthy alternative. The current drying method used widely for making fruit leathers is use of electrical oven and convective hot air drying. The drawback of hot air drying method is a long drying time and the controlling of drying conditions (including increasing drying temperature, decreasing initial moisture content of the puree and so on) will result in the quality of the mango fruit leather. The technology of electrical oven drying method had long been employed to extend the shelf life of foods. However, there is an urgent need to conduct basic studies to investigate the effects of processing on the total drying time and some qualities of the mango fruit leather to optimize the process and set up the processing industry.

The quality of mango fruit leather and the total drying time is directly affected by the drying method, type of dryer, oven design and operating parameters. These parameters must be well established and controlled for each type of fruit leathers. In the production of mango fruit leathers, the puree making process and mixing with other ingredients, the drying temperature, and the puree load on each tray during drying, the total drying time, packaging of the product and appropriate storage conditions should be well established for high quality product. In this study, the effects of processing on some qualities of mango fruit leathers and the total drying time taken are investigated.

1.3 Objectives

The general objective of the thesis work is to study the influence of processing on some quality attributes of mango fruit leathers.

The specific objectives of the thesis are to:

 Produce fruit leather from locally grown mangos

 Conduct physico-chemical analysis of both raw and processed product

 Study the effect of processing on the qualities of the fruit leather

 Suggest a manufacturing process for mango leather production

Significance:

The study is believed to be significant in that it will:

 Reduce postharvest loss of mango fruit in Ethiopia

 Produce the best quality mango leather products

 Reassure the consumer that the mango leather product is safe for consumption

 Optimize the processes for production of good quality mango leather products

Scope:

The study generally covers:

 The processing method for production of mango fruit leather

 Development of mango leather

 Laboratory analysis majorly on: Physico-Chemical Analysis, Proximate Analysis (Nutritional Composition Analysis), Microbiological Analysis

 Sensory Evaluation

 Suggestion of technology and economic analysis

1.4 Structure of the thesis

Fig. 1.1 Structure of the thesis

CHAPTER 2

LITERATURE REVIEW

2.1 Production and marketing of Mango fruits in Ethiopia

The Ethiopian government has a plan to expand mango production by distributing high yielding varieties for small scale farmers, especially in the Southern and Oromia region, by grafting mangos of known and high yielding varieties. In July 2006, it was announced that the Oromia Government distributed 14,000 improved seeds of mango. The production of mango fruits for the past six years in Ethiopia was considered for the study which was found from CSA (2009), and is summarized and presented below in Table 2.1. With an increase in Ethiopian mango crop production and considering the current postharvest loss of mango fruits is at 26.3%, there is not only a need but also a potential for the fruit to be processed into various product types, consequently increasing the market potential of the mango fruit (Kader and Truneh, 2009). Industrial processing opportunities, to increase the market value of the initial fruit, may lead to the potential development of the following products:- Food (mango juice and fizzy drinks, canned fruits and pulp, fruit leather, dried pieces, jam and chutney), domestic (mango detergent and cleaning agents), beauty (as an applied product in skin creams products).

Table 2.1 Estimate of area, production and yield of Mango fruits, Meher season

Year Number of Area in Production in Yield holders hectare quintal (qt/ha)

2003/04 (1996) E.C 350,067 4,964.00 292,283.00 58.88

2004/05 (1997) E.C 414,574 5,814.00 301,715.00 51.89

2005/06 (1998) E.C 463,868 5,400.31 547,291.24 104.06

2006/07 (1999) E.C 558,976 6,796.10 626,111.83 94.08

2007/08 (2000) E.C 695,030 6,730.83 484,360.97 71.96

2008/09 (2001) E.C 716,447 6,051.00 441,582.00 72.97

2.1.1 Exporting Mango fruits

At present, very little mango is exported from Ethiopia with only 4 tonnes exported in 2006 at a value of less than US$1000 according to FAO. This represents a significant decline since 2002 when 811 tonnes were exported at a value of US$675,000 (US$832 per tonne). This appears to have been a particularly high value year however, as the longer term average price for mango exports has been approximately US$323 per tonne. Anecdotal information from key informants suggested that one of the main reasons for the drop in mango exports has been the variable quality of Ethiopian mango exports on arrival in overseas countries. It was reported that Et-Fruit (the state owned Ethiopian Fruit marketing agency) had been exporting mangoes to countries such as Djibouti, Saudi Arabia and UAE but had lost some of those contracts due to the poor quality of the shipments on arrival. This situation highlights the key challenges faced in trying to develop the export market for Ethiopian mangoes: Under-developed packaging and cold chain for exporting, High cost of freight to overseas countries, Competing product from Egypt and South Africa and Minimal production of commercial varieties

In order to begin considering export markets as a viable opportunity, it is essential to consider the nature of demand in export markets. It is very clear that overseas markets are increasingly demanding higher quality, commercial varieties of mangoes, and are also becoming more sophisticated in their preferences for products that are organic. In Asossa then, the first step to even consider export markets would be to begin growing more commercial varieties such as Kent, Keitt and Tommy Atkins. Even if the export market was not a viable option in the short term, these commercial varieties would present a better alternative to the domestic market with less fiber and higher levels of sweetness than existing hybrid varieties (FAO, 2009).

In Ethiopia, the domestic market, consumption is largely in its fresh form due to the fact that the cost increment for processing and packaging would make it beyond the purchasing power of the vast majority of the Ethiopian consumer group (low-income). However, since 1997 the demand for canned fruits in Ethiopia has increased by 7% suggesting there is a sufficient domestic market for canned mangoes to be produced. The mango export markets are where the greatest growth potentials exist for mango producers. The global mango markets are supplied by countries that are strategically positioned to be preferred suppliers. For example, West Africa is a key supplier to Europe due to its proximity to Europe and direct sea-links (Truneh, 2009).

2.1.2 Mango value chain analysis in Ethiopia

Ethiopia is a country that is often associated with famine and food shortage. Whilst this perception is the reality for much of the country at certain times, there are also regions within Ethiopia that are well suited to producing a surplus for particular agricultural commodities. One such location is the Asossa – Homosha region in western Ethiopia, which is particularly suitable to the production of mangoes. In a 2006 study, it was estimated that as much as 28% of the mangoes sold in the capital Addis Ababa, were grown in the Asossa region (WAFC, 2006).

Though the immediate market is small, there is a short and established value chain to Addis Ababa via a 700 km trip. Typically, Asossa exports between 150-300 (10-ton) truckloads of fruit per season to various regions, principally Addis Ababa. In spite of the high cost of imported fruit, nationally the volume has risen by 100% in the last seven years, while that of imported juices has more than doubled in the last four years, evidence of an up-scaling market. The farm-gate price of mangoes in Asossa ranges from 0.25 to 1.15 Birr/kg while the retail price is approximately 5 Birr per kg in Addis, compared to 10 Birr per kg of other imported whole fruits. Farmers typically achieve approximately 5 to 8% of the final retail price (at lower levels) giving them about 1,400Birr in annual income, while wholesalers get about 30% of it but meet the high transport costs. Analysis reveals a reasonably resilient subsector with a favored market position of the ‘Assosa mango’ regional brand. Also, the region appears to have a comparative advantage with ideal growing conditions for mangoes and high yielding trees. At the production level however, the value chain is quite rudimentary with mainly subsistence level cultivation, harvesting and post- handling techniques that limit the quality of the fruit. Upstream there are also issues with most grading and packaging being undertaken following a long road journey to the capital, undermining not only the quality of fruit but also the potential value generated at the farmer level. At the wholesale level in Addis Ababa, market traders dominate the landscape and operate in ways that make it difficult for new entrants to enter the market. Addis wholesalers have strong relationships with the traders based in Asossa and these two levels of the value chain account for most of the final retail price. Given the roles they play, it appears that there is not a proportionate addition of value in the chain, and that is where opportunities lie for improving farmer level value capture in the chain (James et al., 2009).

2.1.3 Asossa market

Within the market in Asossa, there are three main channels for selling mangoes: Farm gate that mainly sell to traders (who sell on to Addis), consumers and small retailers; Asossa Town Market that mainly sell to local consumers and Small Retailers that mainly sell to local consumers. The market is dominated by the open town market where many farmers bring their produce for sale. During peak mango season, this market is saturated with mangoes to the point that prices fall dramatically and many farmers do not even bother to carry their produce home at the end of the day. As well as the open Asossa market, there are a number of kiosk-style small retailers in Asossa which suffer from similar problems at peak supply times. A significant point to note is that much of the mango being supplied at the regional market is not the top grade being produced, but is actually the remaining produce from what has been already sold to traders at farm gate. In this way, traders are siphoning the best quality mangoes to sell in the Addis market, but also provide very little choice to disorganized farmers about where to sell. This study found that farmers on average sell between 0.4 and 1.15 birr depending on quality, and also customer. The lower price tended to be achieved in the Asossa market, with the higher price being received at farm gate from traders purchasing only the higher quality mangoes (Aithal and Wangila, 2006).

2.1.4 Addis Ababa market

The market is dominated by two large wholesale markets, being the Mercato and the Piazza. These markets are the main destination for agricultural produce arriving from around the country. These markets serve not only consumers, but are also where supermarkets, large retailers, hotels and thousands of small kiosk-like retailers source their mangoes. Actual data on the volume of mangoes sold in these markets is very unreliable, however a number of interview sources have identified that in the past five years there has been ‘significant growth’ in market size and increasing consumer demand. This is largely to do with a steadily increasing population (3.2% p.a.), more sophisticated consumer preferences for exotic and tropical fruits, and growing incomes amongst emerging middle and upper class consumers. The average price on the wholesale markets in Addis Ababa was approximately 3.5 birr per kg, or 3,500 birr per tonne, whereas the final retail price in Addis could reach as high as 5 birr per kg (5,000 birr per tonne). By analyzing the price differentials throughout the value chain, it is clear to see that farmers only capture a small portion (8%) of the final retail price. There is no reliable data on the number of small retailers in Addis, but it is estimated there are thousands of street level small retailers/kiosks - some of them dealing

exclusively in fruit, whilst others sell a range of consumable goods. These are a major channel for selling mangoes on to final consumers and are particularly convenient as a street level channel in places of high traffic, with high turnover of goods (CIA, 2008).

Fig. 2.1 Wholesale Mango market in Addis Ababa – Market share by region

Source: (Aithal and Wangila, 2006)

The Mercato and Piazza markets are largely controlled by approximately ten major wholesalers, who deal in fruits and vegetables from all over the country. Industry sources mentioned that the Addis wholesalers are organised under groups that have strong ethnic ties and tend to operate in ways that have been described as ‘cartels’. Similar to the upstream nature of the value chain, the wholesalers in Addis operate in a heavily crowded, poorly structured, and underdeveloped market infrastructure. There is no known refrigerated storage facilities in the market as the cost of this investment has always been seen as too high. The typical wholesale price in Addis is approximately 3,500 birr per tonne and means that Addis wholesalers achieve between 20-40% of the final retail price. This is a considerable portion of the final price and reflects the risk that Addis wholesalers take in ordering mangoes from Asossa. Other value add activities that wholesalers undertake is re- packaging and grading the fruit on arrival in Addis, as produce most often arrives in ‘bulk’ having 10

not yet undergone any systematic grading or packaging. These are functions that are possible at the farm level and may be areas where farmers can extract a greater price and generate more value in the chain (Aithal and Wangila, 2006).

According to a recent update from the mango value chain analysis by James et al., (2009), it has been indicated that within the first six months of the project implementation, the following have been achieved:

• 19 farmer’s cooperatives have been set up and linked to an umbrella cooperative union. Out of these, 100 Cooperative members have been trained on Mango Processing especially in producing jam, juice, compote, vinegar, wine etc. This processing is under taken on site in Asossa.

• Farm gate Price of Mango increased from 25 Birr/100kg to 175 and the farmers have started using weighing scales to measure quantities rather than counting pieces or heaps.

• Between March and June 2009, 357 tonnes of mangoes were sold at the price of 569,084 Birr (roughly USD 46,000) to the most reputable fruit dealer- Et-Fruit for the first time. With World Vision supervision, the income was equitably shared among the farmers.

• 4,000 bottles of various processed mango products like jam, juice, wine and compote have been packed and sold to a number of super markets in Addis Ababa.

• The farmers have entered into partnership with the Ecological Products of Ethiopia, (Ecopia) to process and market mango products.

2.2 Processing of Mango fruits in Ethiopia

The mango processing industry in Ethiopia is in its infant stage. However, mango is grown in many parts, especially in the Rift Valley, western and south-western parts of the country. The national research system has developed a number of varieties but they are not widely spread. Experiences from other countries in growing this crop will therefore contribute to the success and distribution of this fruit. The mango industry in Kenya has expanded considerably over recent years, not only in size but also in the geographical location of commercial and homestead plantings. No longer is commercial mango cultivation restricted to the Coast Province, as significant plantings of improved cultivars now also exist in the Eastern and Central provinces, among other regions (EAP, 2009).

The fruit processing industry in Ethiopia is very weak, considering the substantial amount of fruit that is grown in the country. No doubt, one of the reasons for this is the highly developed processing industries in other countries which are able to export into countries like Ethiopia and sell the final product at low cost. Indeed, there were a number of imported, long-life mango juice brands available throughout Ethiopia and is certain to act as a competitive entry barrier for domestically produced juice. Investigations of local processors found only one significant player, who actually imported frozen mango flesh from India for processing juice in Ethiopia. The main considerations for purchasing Indian imports were the variety, quality, consistency, and price of the imports. When asked about replacing imports with Ethiopian produced mango, the informant indicated that would be his preference, however so far, Ethiopian fruit was not able to compare on the key criteria identified, particularly on price. The informant did however predict that juice processing would begin to emerge as a more viable sector, as mango juice is clearly the most favored juice product by consumers. He indicated that demand for the juice as a category was seeing strong growth, with mango leading this growth. The other key challenges for developing a fruit processing sector in Ethiopia include: lack of technical knowledge in processing, low level of technical support for maintenance, low capital base from which to invest, and many low priced mango juice imports (James et al., 2009).

2.3 Selected Mango varieties for processing

Tommy Atkins Mango variety

It is one of the most popular mangos in the world and cultivated in Florida early 1920's. The Mango cultivar was developed and grown for commercial export. The fruit is a regular oval, medium to large sized, 12 to 24 ounces, yellowish-orange with deep red to purple blush, thicker skinned, juicy but firm with medium fiber.

Pic. 2.1 Tommy Atkins (LFI, 2003)

Keitt Mango variety

Indian strain thought to have originated, like the Haden, from a seedling of Mulgoba 1945, Homestead, Florida. The fruit is a large (20-26 oz.) ovate tapering with slight nose-like protuberance above its tip. Green to orange-yellow as it ripens; firm flesh with a piney sweetness and minimal fiber surrounding the seed area. It is a late fruiting mango, often available into fall.

Pic. 2.2 Keitt (LFI, 2003)

Kent Mango variety

Kent mango was first cultivated in Florida in 1944. It is a direct descendant of the Brooks cultivar, derived from the Sandersha seedling. The fruit is a regular oval shape, large 20 - 26 ounces, with plump cheeks, greenish-yellow color with red shoulder. Very rich and sweet with fiber-free flesh (slices clean to the pit - like butter when ripe!) It is a softer mango that really should not be put to the squeeze test.

Pic. 2.3 Kent (LFI, 2003)

2.4 Medicinal uses and by-products of Mango

Mangos are an excellent source of Vitamins A and C, as well as Potassium, Beta-carotene, enzymes and anti-oxidants. Mangoes are high in fibre, but low in calories (approximately 110 per average sized mango) fat (only 1 g) and sodium. Mangoes are a good staple for your daily diet. It has a reputation (not necessarily scientifically proven) as an alternative or complementary medicine for a wide range of illnesses including beriberi, bronchial diseases, anxiety, insomnia, fatigue, depression, digestive problems heartburn, constipation, kidney stones.

Mango kernel contains high amounts of fat and starch. The oil extracted from kernel is of good quality and could be used in cosmetic and soap industries. The kernel flour (starch) after mixing with wheat or maize flour is used in chapattis in India. About ten percent alcohol could be obtained from mango kernel by co-culture fermentation (Truneh, 2009).

2.5 Mango processing technologies

The processing of fruits has two objectives. Firstly, to preserve by slowing down the natural processes of decay caused by microorganisms, enzymes in the food, or other factors such as heat, moisture and sunlight. The second objective is to convert them into different foods which are attractive and in demand by consumers Food Processors should utilize their skills to develop recipes and create attractive products that consumers want to eat. Thereby successful Food Processors increase product sales and generate profits. Food Processors must select their products with caution. It is not enough to assume that processing can be a successful business simply because there a large quantities of cheap fruit available in the marketplace. There must be a good demand for the end product and this must be clearly identified before designing and investing in the business. The best types of products for small-scale production are those that have a high ‘added- value’ as well as a good demand. A high added value means that cheap raw materials can be processed into relatively expensive products. It also means that this can be done at a small scale of processing, using equipment that is affordable (Fellows and Quaouich, 2004).

Fruits like mangos, pawpaw, guavas and bananas, can easily be dried. However, they should be harvested at the right stage and ripeness. Hard ripe stage in mangoes, pawpaw and bananas gives best results. Avoid overripe, under mature fruits in order to obtain good products. To prepare the fruits for drying, wash them thoroughly with clean water. Scrubbing with a brush might be necessary like in case of mango fruit with a lot of latex cover. The fruits are peeled if necessary and cut into smaller uniform pieces to ensure faster drying. Stainless steel knives are recommended for peeling and cutting of the slices or pieces. To avoid discoloration and excessive vitamin losses, treatment with anti-oxidants like citrus (lemon) juice is done. Fruits like pineapples may require pre-cooking to soften fibrous tissue hence hasten drying. Drying is done on trays, which should be made of wood, fabric, plastic or sisal material. This is because metal materials may affect the drying product negatively e.g. copper destroys vitamin C, iron rusts, aluminum discolors fruits and corrodes. Most fruits have natural acids and sugars which are preservatives therefore moisture contents of about 20% i.e. leathery and springy dry (not brittle) is good for storage. This is however dependent on the fruit or vegetable. After the correct stage of dryness is achieved the product should be removed from the dryer parked, and stored in a dry, dark store to avoid loss of vitamin A (GTZ, 2009).

Mangos are processed at two stages of maturity. Green fruit is used to make chutney, pickles, curries and dehydrated products. The green fruit should be freshly picked from the tree. Fruit that is bruised, damaged, or that has prematurely fallen to the ground should not be used. Ripe mangoes are processed as canned and frozen slices, puree, juices, nectar and various dried products. Mango processing within the home and cottage industries converts the fruit into many other products. Mango processing presents many problems as far as industrialization and market expansion is concerned. The trees are alternate bearing and the fruit has a short storage life; these factors make it difficult to process the crop in a continuous and regular way. The large number of varieties with their various attributes and deficiencies affects the quality and uniformity of processed products. Additionally, the lack of simple, reliable methods for determining the stage of maturity of varieties for processing also affects the quality of the finished products. Many of the processed products require peeled or peeled and sliced fruit. Within Ethiopia the lack of mechanized equipment for the peeling of ripe mangoes is a serious bottleneck for increasing the production of these products. A significant problem in developing mechanized equipment is the large number of varieties available and their different sizes and shapes. The cost of processed mango products is also too expensive for the general population in the areas where most mangoes are grown. However, there is a

considerable export potential to developed countries but in these countries the processed mango products must compete with established processed fruits of high quality and relatively low cost (Dauthy, 1995).

2.5.1 Ripe Mango processing

Mango Puree

Mangoes are processed into puree for re-manufacturing into products such as nectar, juice, squash, jam, jelly, dehydrated products such as fruit leathers. The puree can be preserved by chemical means, or frozen, or canned and stored in barrels. This allows a supply of raw materials during the remainder of the year when fresh mangoes are not available. It also provides a more economical means of storage compared with the cost of storing the finished products, except for those which are dehydrated, and provides for more orderly processing during peak availability of fresh mangoes. Mangoes can be processed into puree from whole or peeled fruit. Because of the time and cost of peeling, this step is best avoided but with some varieties it may be necessary to avoid off- flavors which may be present in the skin. The most common way of removing the skin is hand- peeling with knives but this is time-consuming and expensive. Steam and lye peeling have been accomplished for some varieties. Several methods have been devised to remove the pulp from the fresh ripe mangoes without hand-peeling. A simplified method is as follows: the whole mangoes were exposed to atmospheric steam for 2 to 2 and 1/2 min in a loosely covered chamber, and then transferred to a stainless steel tank. The steam-softened skins allowed the fruit to be pulped by a power stirrer fitted with a saw-toothed propeller blade mounted 12.7 to 15.2 cm below a regular propeller blade. The pulp is removed from the seeds by a continuous centrifuge designed for use in passion fruit extraction. The pulp material is then passed through a paddle pulper fitted with a 0.084 cm screen to remove fiber and small pieces of pulp.

Mango puree can be frozen, canned or stored in barrels for later processing. In all these cases, heating is necessary to preserve the quality of the mango puree. In one process, puree is pumped through a plate heat exchanger and heated to 90°C for 1 min and cooled to 35° C before being filled into 30 lb tins with polyethylene liners and frozen at -23.50 C. In another process, pulp is acidified to pH 3.5, pasteurized at 90°C, and hot-filled into 6 kg high-density bulk polyethylene containers that have been previously sterilized with boiling water. The containers are then sealed and cooled in water. This makes it possible to avoid the high cost of cans. Wooden barrels may be used to store mango pulp in the manufacture of jams and squashes. The pulp is acidified with 0.5 to 16

1.0% citric acid, heated to boiling, cooled, and SO2 is added at a level of 1000 to 1500 ppm in the pulp. The pulp is then filled into barrels for future use.

Dried/dehydrated Mango

Ripe mangoes are dried in the form of pieces, powders and flakes. Drying procedures such as sun- drying, tunnel dehydration, vacuum-drying, osmotic dehydration may be used. Packaged and stored properly, dried mango products are stable and nutritious. One described process involves as pre- treatment dipping mango slices for 18 hr (ratio 1:1) in a solution containing 40° Brix sugar, 3000 ppm SO2, 0.2% ascorbic acid and 1% citric acid; this method is described as producing the best dehydrated product. Drying is described using an electric cabinet through flow dryer operated at 60° C. The product showed no browning after 1 year of storage (Dauthy, 1995). Mango fruits can also be dried in the form of leathers or bars.

2.6 Fruit leather processing

Fruit leathers are dried sheets of fruit pulp which have a soft, rubbery texture and a sweet taste. They can be made from most fruits, although mango, apricot, banana and tamarind leathers are amongst the most popular. Leathers can also be made from a mixture of fruits. Fruit leathers are eaten as snack foods instead of boiled sweets. They are also used as ingredients in the manufacture of cookies, cakes and ice cream. The preservation of fruit leathers depends on their low moisture content (15-25%), the natural acidity of the fruit and the high sugar content. When properly dried and packaged, fruit leathers have a shelf life of up to 9 months (FPT, 2009).

2.6.1 Preparation of fruits

Fruit should be washed in clean water, peeled and the stones removed. Washing water can be chlorinated by adding 1 teaspoon of bleach to 4.5 liters of water. All fruit should be ripe and free from bruising. Any rotten or bruised fruit should be thrown away as this will spoil the color and flavor of the leather. The puree must be heated to a higher temperature for a longer time to destroy the enzyme (it must be boiled for 20 minutes). Only stainless steel knives should be used to chop the fruit. Other metals will discolor the fruit flesh. At the simplest level, fruit is made into a puree by hand using a food mill. If electricity is available, a liquidizer or blender can be used to increase the production output. The liquidized fruit is strained or sieved to remove the fibers, seeds, etc to make a smooth puree. Fruit puree can be semi-processed and stored in sealed drums for further processing later in the season. Sulphur dioxide (SO2) (600ppm) is added to the drums to prevent the 17

growth of micro-organisms. The semi-processed fruit can be stored for several months. Chemical preservatives may be added to the fruit puree to maintain a bright color in the leather. Preservatives are also added if the puree is to be stored before processing. A variety of ingredients can be added to the fruit puree - sugar to increase the sweetness, citric acid to increase the acidity and chopped nuts, coconut or spices to vary the taste and flavor.

2.6.2 Heating, drying and packaging

The puree must be heated to 900 C to inactivate the enzymes and reduce the level of microbiological contamination. A double pan boiler is recommended for heating to avoid burning the puree. The fruit puree is poured in a thin layer (3-6mm thick) on plastic trays or wooden trays lined with greaseproof paper. The puree can be poured into a square which is later cut into small pieces, or into small circles which are rolled up when dry. The leathers should not be dried in direct sunlight as this will cause the color to fade and reduce the levels of vitamins A and C. Indirect solar dryers or mechanical dryers should be used. The leather should be dried overnight in a solar dryer or for about 5 hours in a mechanical dryer. After this time it is turned over and dried on the other side. The leather is dried until it has a final moisture content of 15-25%. After drying, the leather pieces should be dusted lightly with starch to prevent them sticking together. All equipment must be thoroughly cleaned each day to prevent contamination by insects and micro-organisms.

In developing countries fruit leather is usually packaged cheaply with easily sourced materials. The fruit leather is sold as a roll that is interleaved with greaseproof paper to prevent it from sticking together. Strips of the leather are weighed, laid on a piece of greaseproof paper and rolled with the paper. The rolls or discs of leather are packed in polythene or polypropylene heat-sealed bags. The bags should be placed in boxes to protect them from the light. Fruit leather products in Europe are packaged as a bar or as mini sweets, within a sealed plastic/foil case. The fruit leather bars within their plastic/foil case may be packaged and sold as a multipack within a cardboard box made from recycled paper products. The attractive, modern design of the packaging is specifically aimed at the health conscious, luxury product niche within the consumer market (FPT, 2009).

2.7 Mango fruit leather recipes and processing procedures

The following basic recipes are only guidelines since they depend on the composition of fruit (which varies between different types) and the different consumer tastes for sweetness. The recipes needed for mango leather preparation are: fully ripe mango, Sugar (10-15% the pulp weight according to the variety used and consumer taste), lemon juice or citric acid 2 spoons per kg pulp), Sodium of potassium metabisulphite (2g per kg pulp), and Glycerin for foods.

The general procedure for making mango fruit leather is as follows:

1. Wash the mangoes in clean water. Drain, Sort and remove any unripe or over-ripe fruit.

2. Peel the fruit with a stainless steel knife and cut the flesh into small pieces.

3. Extract the pulp using a pulper.

4. Weigh the pulp and mix with the sugar, lemon juice and metabisulphite in the ratios above.

5. Heat at 70-80 0C.

6. Remove the foam from the top of the mixture. Grease the surface of trays with glycerin to prevent the leather from sticking.

7. Pour the hot puree onto the trays at a ratio of 15kg per square meter of tray area.

8. Place the trays in a dryer. Leave to dry until a final moisture content of 15%. The product will have a soft, leather-like consistency.

9. Place three sheets of leather on top of each other and cut into small 4x4cm squares. Wrap each square in cellophane. It may be necessary to dust the squares with corn flour to prevent excess stickiness.

10. Pack in plastic bags, label and store in a cool dry place (FPT, 2009).

Mango fruit leather can also be made using electric dehydrator or drying oven. Andress (2004) formulated mango fruit leather with different recipes and methods as described below.

Recipes: include; 4 cups mango puree (from about 4 large, unripe mangoes), 1 cup clover honey, ½ teaspoon ground cinnamon, ¼ teaspoon ground nutmeg, and ¼ teaspoon ground cloves. 19

Yield: about 2 dryer trays (14 inches in diameter); 8 fruit rolls.

2.7.1 Adding sweeteners and flavoring to fruit leather

Once you have the basics of making fruit leathers it is fun to try some new flavoring, toppings, or fillings. Below are some new ideas.

Sweetening - If the puree needs some sweetening, add up to ½ cup sugar for each 2 cups of fruit. Sugar substitutes may be used. Aspartame sweeteners however may lose sweetness during drying.

Spices – Add spices to the puree. Add until the taste is acceptable. Begin by adding 1/8-teaspoon for each 2 cups of puree’. Try: cinnamon, cloves, ginger, mint, nutmeg, allspice.

Flavorings – Add flavorings to the puree using only 1/8-teaspoon person 2 cups of puree to start. Try almond extract, lemon peel, orange extract, vanilla or peppermint.

Toppings – After spreading the puree on the drying sheet and before drying, sprinkle a topping over the puree. Try not to cover entire puree, but just lightly sprinkle the topping. Try coconut, dried fruits, granola, and sunflower seeds.

Fillings – After the fruit leather is dried and cool, spread a thin layer of these fillings. Then roll, cut and serve. If not served immediately, store in the refrigerator or wait to spread filling until just before serving. Try – melted chocolate, softened cream cheese, peanut butter, marshmallow cream, jam or jelly. Here is an idea for adding dairy foods and calcium to your diet in a fun tasty way.

Yogurt Drops - 18-ounce vanilla yogurt, 13-oz package of sugar free gelatin powder (any flavor) and mix the gelatin powder with the yogurt. Using a spoon drop the mixture onto a fruit leather drying tray. They can be done in small rounds or as leather. Dry until sticky and store in the refrigerator or freezer. This makes great healthy snack and provides another way to get dairy products and calcium in the diet (Brown, 2009).

2.8 Quality control

Quality control begins with the acquisition of high-quality fruit concentrate. Many purees are supplied by well-known fruit processors. Other quality control methods include careful calibration of all additives, particularly of those additives that affect hardening/malleability (malto-dextrin in particular). Also, cooking and drying temperatures are monitored closely to ensure moisture content. Scales are carefully calibrated so that each roll contains just the right amount of extruded 20 product; similarly, the packaging machine is checked and re-checked so that each cardboard package includes the correct number of fruit leathers. Sample testing is performed periodically as well (Nancy, 2009).

One of the most important concerns of the food manufacturer is to produce a final product that consistently has the same overall properties, i.e. appearance, texture, flavor and shelf life. When we purchase a particular food product we expect its properties to be the same (or very similar) to previous times, and not to vary from purchase-to-purchase. Ideally, a food manufacture wants to take the raw ingredients, process them in a certain way and produce a product with specific desirable properties. Unfortunately, the properties of the raw ingredients and the processing conditions vary from time to time which causes the properties of the final product to vary, often in an unpredictable way. How can food manufacturers control these variations? Firstly, they can understand the role that different food ingredients and processing operations play in determining the final properties of foods, so that they can rationally control the manufacturing process to produce a final product with consistent properties. This type of information can be established through research and development work (see later). Secondly, they can monitor the properties of foods during production to ensure that they are meeting the specified requirements, and if a problem is detected during the production process, appropriate actions can be taken to maintain final product quality (McClements, 1999).

Quality control points:

• Use only ripe fruits without bruising or damage. Over-ripe ones can easily become damaged and bruised. Under-ripe fruits will not have the full flavor.

• Use a double boiling pan to avoid burning which can occur if direct heating is used.

• Weigh all ingredients to the correct formulation.

• Do not dry the leather in direct sunlight as there will be loss of color and vitamins A and C.

• Dust the leather lightly with starch before packing to reduce their stickiness.

• Seal the leather packed in the form of a roll interleaved with greaseproof paper to avoid it sticking together.

• Check the correct fill-weight before sealing the bags.

• If available, use 400 gauge polypropylene bags as they provide greater protection against moisture (Nancy, 2009).

Manufacturers measure the properties of incoming raw materials to ensure that they meet certain minimum standards of quality that have previously been defined by the manufacturer. If these standards are not met the manufacturer rejects the material. Even when a batch of raw materials has been accepted, variations in its properties might lead to changes in the properties of the final product. By analyzing the raw materials it is often possible to predict their subsequent behavior during processing so that the processing conditions can be altered to produce a final product with the desired properties. Monitoring of food properties during processing is advantageous for food manufacturers to be able to measure the properties of foods during processing. Thus, if any problem develops, then it can be quickly detected, and the process adjusted to compensate for it. This helps to improve the overall quality of a food and to reduce the amount of material and time wasted. Traditionally, samples are removed from the process and tested in a quality assurance laboratory. This procedure is often fairly time-consuming and means that some of the product is usually wasted before a particular problem becomes apparent. For this reason, there is an increasing tendency in the food industry to use analytical techniques which are capable of rapidly measuring the properties of foods on-line, without having to remove a sample from the process. These techniques allow problems to be determined much more quickly and therefore lead to improved product quality and less waste. The ideal criteria for an on-line technique is that it be capable of rapid and precise measurements, it is non-intrusive, it is nondestructive and that it can be automated. Once the product has been made it is important to analyze its properties to ensure that it meets the appropriate legal and labeling requirements, that it is safe, and that it is of high quality. It is also important to ensure that it retains its desirable properties up to the time when it is consumed (McClements, 1999).

2.9 Effect of processing on food quality attributes

Foods undergo changes as a result of processing; such changes may be physical, chemical, enzymatic, or microbiological (Singh & Heldman, 2001). Food processing is any and all processes to which food is subjected after harvesting for the purposes of improving its appearance, texture, palatability, nutritive value, keeping properties and ease of preparation, and for eliminating microorganisms, toxins and other undesirable constituents (David & Arnold,1999). 22

The composition of a food largely determines its safety, nutrition, physicochemical properties, quality attributes and sensory characteristics. Most foods are compositionally complex materials made up of a wide variety of different chemical constituents. Their composition can be specified in a number of different ways depending on the property that is of interest to the analyst and the type of analytical procedure used: specific atoms (e.g., Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur, Sodium, etc.); specific molecules (e.g., water, sucrose, tristearin, b-lactoglobulin), types of molecules (e.g., fats, proteins, carbohydrates, fiber, minerals), or specific substances (e.g., peas, flour, milk, peanuts, butter). Government regulations state that the concentration of certain food components must be stipulated on the nutritional label of most food products, and are usually reported as specific molecules (e.g., vitamin A) or types of molecules (e.g., proteins) (McClements, 1999).

Many unit operations, especially those that do not involve heat, have little or no effect on the nutritional quality of foods. Examples include mixing, cleaning, sorting, freeze drying and pasteurization. Unit operations that intentionally separate the components of foods alter the nutritional quality of each fraction compared with the raw material. Unintentional separation of water-soluble nutrients (minerals, water-soluble vitamins and sugars) also occurs in some unit operations (for example blanching, and in drip losses from roast or frozen foods.

Processing using heat is a major cause of changes to nutritional properties of foods. For example gelatinization of starches and coagulation of proteins improve their digestibility, and anti- nutritional compounds (for example a trypsin inhibitor in legumes) are destroyed. However, heat also destroys some types of heat-labile vitamin, reduces the biological value of proteins (owing to destruction of amino acids or Maillard browning reactions) and promotes lipid oxidation. Therefore a continuing aim of food manufacturers should be to find improvements in processing technology which retain or create desirable sensory qualities and nutritional properties or reduce the damage to food caused by processing (Fellows, 2000).

2.9.1 Physicochemical properties

The physiochemical properties of foods (rheological, optical, stability, “flavor”) ultimately determine their perceived quality, sensory attributes and behavior during production, storage and consumption. The optical properties of foods are determined by the way that they interact with electromagnetic radiation in the visible region of the spectrum, e.g., absorption, scattering, transmission and reflection of light. For example, full fat milk has a “whiter” appearance than skim 23

milk because a greater fraction of the light incident upon the surface of full fat milk is scattered due to the presence of the fat droplets.

The rheological properties of foods are determined by the way that the shape of the food changes, or the way that the food flows, in response to some applied force. For example, margarine should be spread able when it comes out of a refrigerator, but it must not be so soft that it collapses under its own weight when it is left on a table. The stability of a food is a measure of its ability to resist changes in its properties over time. These changes may be chemical, physical or biological in origin. Chemical stability refers to the change in the type of molecules present in a food with time due to chemical or biochemical reactions, e.g., fat rancidity or non-enzymatic browning. Physical stability refers to the change in the spatial distribution of the molecules present in a food with time due to movement of molecules from one location to another, e.g., droplet creaming in milk. Biological stability refers to the change in the number of microorganisms present in a food with time, e.g., bacterial or fungal growth. Foods must therefore be carefully designed so that they have the required physicochemical properties over the range of environmental conditions that they will experience during processing, storage and consumption, e.g., variations in temperature or mechanical stress. Consequently, analytical techniques are needed to test foods to ensure that they have the appropriate physicochemical properties (McClements, 1999).

2.9.2 Changes on Vitamins

Vitamins are minor components of foods which play an essential role in human nutrition. They are organic compounds that are necessary in small amounts for proper growth. In general human beings and animals can not be in a healthy state without vitamins, carbohydrates, fats, proteins, minerals and water. Very small quantities of vitamins are necessary for health, but a lack of them may upset the normal metabolism, resulting in deficiency diseases. Many of the vitamins are unstable under certain conditions of processing and storage and their levels in processed foods, therefore, may be considerably reduced. Most of the vitamins are also heat sensitive. The occurrence of the vitamins in the various food groups is related to their water or fat solubility. Vitamins are classified into two main groups: water soluble vitamins and Fat soluble vitamins (Deman, 1980).

2.9.2.1 Effects of preliminary treatments: trimming and washing on Vitamins

The peeling and trimming of fruits and vegetables can cause losses of vitamins to the extent that they are concentrated in the discarded stem, skin, or peel fractions. Although this can be a source of significant loss relative to the intact fruit or vegetable, in most cases this must be considered to be an inevitable loss regardless of whether it occurs in industrial processing or home preparation. Alkaline treatments to enhance peeling can cause increased losses of labile vitamins such as float, ascorbic acid, and thiamin at the surface of the product. However, losses of this kind tend to be small compared to the total vitamin content of the product. Any exposure of cut or otherwise damaged tissues of plant or animal products to water or aqueous solutions causes the loss of water- soluble vitamins by extraction (leaching). This can occur during washing, transportation via flumes, and exposures to brines during cooking. The extent of such losses depends on factors that influence the diffusion and solubility of the vitamin, including pH (can affect solubility and dissociation of vitamins from binding sites within the tissue), ionic strength of the extract, temperature, the volume ratio of food to aqueous solution, and the surface-to-volume ratio of the food particles (Fennema, 1996).

2.9.2.2 Effects of blanching and thermal processing on Vitamins

Blanching, a mild heat treatment is an essential step in the processing of fruits and vegetables. The primary purposes are to inactivate potentially deleterious enzymes, reduce microbial loads, and decrease interstitial gasses prior to further processing. Inactivation of enzymes often has a beneficial effect on the stability of many vitamins during subsequent food storage. Blanching can be accomplished in hot water, flowing steam, hot air, or with microwaves. Losses of vitamins occur primarily by oxidation and aqueous extraction (leaching), with heat being a factor of secondary importance. Blanching in hot water can cause large losses of water-soluble vitamins by leaching. It has been well documented that high-temperature, short-time treatments improve retention of labile nutrients during blanching and other thermal processes. The elevated temperature of thermal processing accelerates reactions that would otherwise occur more slowly at ambient temperature. Thermally induced losses of vitamins depend on the chemical nature of the food, its chemical environment (pH, relative humidity, transition metals, other reactive compounds, concentration of dissolved oxygen, etc.), the stabilities of the individual forms of vitamins present, and the opportunity for leaching. The nutritional significance of such losses depends on the degree of loss

and the importance of the food as a source of the vitamin in typical diets (Da-Silva and Williams, 1991).

2.9.2.3 Effect of processing on Vitamin C

Vitamin C (L-ascorbic acid) is the least stable of all vitamins and will easily be destroyed during processing and storage. The rate of destruction of vitamin C is increased by the action of metals, especially copper and iron, and also by the action of enzymes. Exposure to oxygen and light and prolonged heating in the presence of oxygen during processing will decrease the vitamin C content of foods. Factors that affect vitamin C destruction during processing include heat treatment and leaching. The severity of processing conditions can often be judged by the percentage of ascorbic acid that has been lost. The extent of loss depends on the amount of water used. Vegetables during blanching covered with water may lose 80% half covered 40% and quarter covered 40% of the ascorbic acid. Particle size affects the loss, for example in blanching of small pieces of carrots, losses may range from 32-50% and losses from large pieces only 22-33%. Blanching of cabbage may result in 20% loss of ascorbic acid and subsequent dehydration may increase this to a total of 50%. In the processing of milk losses may occur at various stages. From an initial level of about 22mg/l in raw milk the content in the product reaching the consumer may be well below 10mg per liter. Ascorbic acid is oxidized in the presence of air under neutral and alkaline conditions. At acid pH the vitamin is more stable for example in citrus juice. Since oxygen is required for the breakdown, removal of oxygen should have a stabilizing effect. For the production of fruit drinks it is recommended to de-aerate the water to minimize the vitamin C loss. The type of container may also affect the extent of ascorbic acid destruction. Use of tin cans for fruit juices result in rapid depletion of oxygen by the electrochemical process of corrosion. In bottles all of the residual oxygen is available for ascorbic acid oxidation. To account for processing and storage losses it is common to allow for a loss of 7-14mg of ascorbic acid per 100ml of fruit juice (Fennema, 1996).

2.9.3 Flavor and pigment components

The flavor of a food is determined by the way that certain molecules in the food interact with receptors in the mouth (taste) and nose (smell) of human beings. The perceived flavor of a food product depends on the type and concentration of flavor constituents within it, the nature of the food matrix, as well as how quickly the flavor molecules can move from the food to the sensors in the mouth and nose. Analytically, the flavor of a food is often characterized by measuring the

concentration, type and release of flavor molecules within a food or in the headspace above the food (McClements, 1999).

Fresh foods contain complex mixtures of volatile compounds, which give characteristic flavors and aromas, some of which are detectable at extremely low concentrations (Fellows, 2000). These compounds may be lost during processing, which reduces the intensity of flavor or reveals other flavor/aroma compounds. Volatile aroma compounds are also produced by the action of heat, ionizing radiation, and oxidation or enzyme activity on proteins, fats and carbohydrates. Examples include the Maillard reaction between amino acids and reducing sugars or carbonyl groups and the products of lipid degradation or hydrolysis of lipids to fatty acids and subsequent conversion to aldehydes, esters and alcohols. The perceived aroma of foods arises from complex combinations of many hundreds of compounds, some of which act synergistically (Maruniak and MacKay-Sim, 1984). In addition, the perceived flavor of foods is influenced by the rate at which flavor compounds are released during chewing, and hence is closely associated with the texture of foods and the rate of breakdown of food structure during mastication (Clark, 1990).

The colors of foods are the result of the presence of natural pigments or of added dyes. Pigments are a group of natural colorants found in animal and vegetable products (Deman, 1980). These pigments are organic in their nature and generally considered to embrace the pigments already formed in the foods as well as those which can be formed on heating, storage or processing. Many naturally occurring pigments are destroyed by heat processing, chemically altered by changes in pH or oxidized during storage. As a result the processed food may lose its characteristic color and hence its value. Maillard browning is an important cause of both desirable changes in food color (for example in baking or frying and in the development of off-colors (for example during canning and drying. Major food processing activities such as ambient temperature processing, processing by the application of heat and processing by the removal of heat will affect the flavor, aroma and pigment of food stuffs (Fellows, 2000).

2.9.3.1 Heat induced processing effects on flavor and color

Most foods have no significant changes to flavor or aroma when correctly blanched, but under- blanching can lead to the development of off-flavors during storage of dried or frozen foods. In fruit juices the main cause of color deterioration is enzymatic browning by polyphenoloxidase. This is promoted by the presence of oxygen, and fruit juices are therefore routinely de-aerated prior to pasteurization. In fruits and vegetables, chlorophyll is converted to pheophytin, carotenoids are 27

isomerized from 5, 6-epoxides to less intensely colored 5, 8-epoxides, and anthocyanins are degraded to brown pigments. Changes are due to complex reactions which involve the degradation, recombination and volatilization of aldehydes, ketones, sugars, lactones, amino acids and organic acids. In aseptically sterilized foods the changes are again less severe, and the natural flavors of milk, fruit juices and vegetables are better retained. Aroma compounds that are more volatile than water can be lost during evaporation. This reduces the sensory characteristics of most concentrates; in fruit juices this results in loss of flavor, although in some foods the loss of unpleasant volatiles improves the product quality, for example in cocoa (Anon, 1981).

Heat not only vaporizes water during drying but also causes loss of volatile components from the food and as a result most dried foods have less flavour than the original material. The extent of volatile loss depends on the temperature and moisture content of the food and on the vapor pressure of the volatiles and their solubility in water vapor. Volatiles which have a high relative volatility and diffusivity are lost at an early stage in drying. Foods that have a high economic value due to their characteristic flavors (for example herbs and spices) are dried at low temperatures (Mazza and LeMaguer, 1980).

The open porous structure of dried food allows access of oxygen, which is a second important cause of aroma loss due to oxidation of volatile components and lipids during storage. Most fruits and vegetables contain only small quantities of lipid, but oxidation of unsaturated fatty acids to produce hydro peroxides, which react further by polymerization, dehydration or oxidation to produce aldehydes, ketones and acids, causes rancid and objectionable odours. Some foods (for example carrot) may develop an odour of ‘violets’ produced by the oxidation of carotenes to - ionone (Rolls and Porter, 1973). Evaporation darkens the color of foods, partly because of the increase in concentration of solids, but also because the reduction in water activity promotes chemical changes, (for example Maillard browning). As these changes are time and temperature dependent, short residence times and low boiling temperatures produce concentrates which have a good retention of sensory and nutritional qualities (Anon, 1981). Blanching brightens the color of some foods by removing air and dust on the surface and thus altering the wavelength of reflected light. The time and temperature of blanching also influence the change in food pigments according to their D value (Fellows, 2000).

2.9.4 Sensory attributes

The quality and desirability of a food product is determined by its interaction with the sensory organs of human beings, e.g., vision, taste, smell, feel and hearing. For this reason the sensory properties of new or improved foods are usually tested by human beings to ensure that they have acceptable and desirable properties before they are launched onto the market. Even so, individuals' perceptions of sensory attributes are often fairly subjective, being influenced by such factors as current trends, nutritional education, climate, age, health, and social, cultural and religious patterns. To minimize the effects of such factors a number of procedures have been developed to obtain statistically relevant information. For example, foods are often tested on statistically large groups of untrained consumers to determine their reaction to a new or improved product before full-scale marketing or further development. Alternatively, selected individuals may be trained so that they can reliably detect small differences in specific qualities of particular food products, e.g., the mint flavor of a chewing gum Although sensory analysis is often the ultimate test for the acceptance or rejection of a particular food product, there are a number of disadvantages: it is time consuming and expensive to carry out, tests are not objective, it cannot be used on materials that contain poisons or toxins, and it cannot be used to provide information about the safety, composition or nutritional value of a food. For these reasons objective analytical tests, which can be performed in laboratory using standardized equipment and procedures, are often preferred for testing food product properties that are related to specific sensory attributes. For this reason, many attempts have been made to correlate sensory attributes (such as chewiness, tenderness, or stickiness) to quantities that can be measured using objective analytical techniques, with varying degrees of success (McClements, 1999).

Many types of food processing techniques have been employed throughout human history, mainly to ensure microbiological and chemical safety of foods and to improve palatability. Growing consumer demand for healthy, nutritious and convenient food is a key driver for improvements and new developments in food processing. New processes or newly recognized compounds, often identified due to improved analytical capabilities, require careful evaluation of potential human health impact. The most important quality attributes of a food to the consumer, are its sensory characteristics (texture, flavor, aroma, shape and color). These determine an individual’s preference for specific products, and small differences between brands of similar products can have a substantial influence on acceptability. So during processing great care must be taken to retain or enhance these properties (Fellows, 2000). 29

2.9.5 Influence of drying process

Fruits like mangoes, pawpaw, guavas and bananas, can easily be dried. However, they should be harvested at the right stage and ripeness. Hard ripe stage in mangoes, pawpaw and bananas gives best results. Avoid overripe, under mature fruits in order to obtain good products. To prepare the fruits for drying, wash them thoroughly with clean water. Scrubbing with a brush might be necessary like in case of mango fruit with a lot of latex cover. The fruits are peeled if necessary and cut into smaller uniform pieces to ensure faster drying. Stainless steel knives are recommended for peeling and cutting of the slices or pieces. Drum-drying of mango puree is described as an efficient, economical process for producing dried mango powder and flakes. Its major drawback is that the severity of heat preprocessing can produce undesirable cooked flavors and aromas in the dried product. The drum-dried products are also extremely hydroscopic and the use of in-package desiccant is recommended during storage (Dauthy, 1995).

To avoid discoloration and excessive vitamin losses, treatment with anti-oxidants like citrus (lemon) juice is done. Fruits like pineapples may require pre-cooking to soften fibrous tissue hence hasten drying. Drying is done on trays, which should be made of wood, fabric, plastic or sisal material. This is because metal materials may affect the drying product negatively e.g. copper destroys vitamin C, iron rusts, aluminum discolors fruits and corrodes. Most fruits have natural acids and sugars which are preservatives therefore moisture contents of about 20% i.e. leathery and springy dry (not brittle) is good for storage. This is however dependent on the fruit or vegetable. After the correct stage of dryness is achieved the product should be removed from the dryer parked, and stored in a dry, dark store (GTZ, 2009).

2.10 Food safety

One of the most important reasons for analyzing foods from both the consumers and the manufacturer’s standpoint is to ensure that they are safe. It would be economically disastrous, as well as being rather unpleasant to consumers, if a food manufacturer sold a product that was harmful or toxic. A food may be considered to be unsafe because it contains harmful microorganisms (e.g., Listeria, Salmonella), toxic chemicals (e.g., pesticides, herbicides) or extraneous matter (e.g., glass, wood, metal, insect matter). It is therefore important that food manufacturers do everything they can to ensure that these harmful substances are not present, or that they are effectively eliminated before the food is consumed. This can be achieved by following “good manufacturing practice” regulations specified by the government for specific food products and by having analytical techniques that are capable of detecting harmful substances. In many situations it is important to use analytical techniques that have a high sensitivity, i.e., that can reliably detect low levels of harmful material. Food manufacturers and government laboratories routinely analyze food products to ensure that they do not contain harmful substances and that the food production facility is operating correctly (McClements, 1999).

CHAPTER 3

MATERIALS AND METHODS

3.1 Raw material source and equipment

The raw materials needed for the research are ripened mango fruits. Mango fruits were collected from Et-fruit, the Keitt variety mangos were brought from Assossa region and the Tommy Atkins variety of mangos were brought from Awara Melka in Afar region. The honey used as a sweetener was collected from Gojam area, a typical place called Debre Markos, and traditionally purified at home. The lemon used for making juice as a source of ascorbic acid for preserving the mango puree color and as flavoring agent was bought from Atkilt Tera market in Addis Ababa. The spice ingredient as a flavoring agent was ground ginger obtained from Mercato.

The equipments required for developing Mango leather were scales, plastic containers to wash fruit, stainless steel knives, spoons, chopping boards, water bath fitted with thermostat, fruit pulper, large sealable food grade bins for intermediate storage of pulps, convective hot air dryer or drying oven, and heat sealer.

3.2 Approach for selection and preparation of Mango fruits

The mango market in Addis Ababa is mainly dominated with the local mango varieties. The mangos brought by Et-Fruit to the market are generally classified as local and export standards. Normally the export standard mangos are from Tommy Atkins and Kent varieties which are being cultivated by the Upper Awash Agro-industry farm and are directly exported most of the time. These varieties are also cultivated by the Awash Melkasa Agricultural Research Institute (AMARI). However, this research was not conducted at the peak harvest season of these varieties of mangos. As a result the experimental work has been initiated with the available Keitt varieties.

Preliminary studies were carried out to determine the appropriate tray load of the Mango leather and drying time to produce satisfactory product using Tommy Atkins and Keitt varieties of mango fruits. The pH of the puree was measured by pH meter, titerable acidity and total soluble solid content of the fruit pulps were determined by AOAC methods (1984).

3.3 Development of Mango fruit leather

Both Keitt and Tommy Atkins varieties of Mango fruits were brought to Addis Ababa University, Department of Chemical Engineering Laboratory, and processed individually with the same procedure. Immediately after the fruits arrival, the ripened and unspoiled fruits were selected, sorted and washed properly. Some of the mango fruits with minor blemishes and bruises that couldn’t be suitable for other processes like canning or freezing were also used for this leather product development as the process is based on drying principle. Accordingly, the mangos were weighed after the blemishes were cut away and were manually peeled with a stainless steel knife. They were cut and sliced in to pieces, and the stones and peels were also weighed. These were removed to make fruit pulp ready for making the puree. The pulp was pureed in blender till becoming smooth. The pure mango puree was covered and put into a glass jar and refrigerated at 40C. The puree mix was prepared with the proportion of 1kg of Mango puree, 39.4g of honey, 18.2g of lemon juice and 3.1g of ground ginger. This was done based on preliminary test as to the material balance.

3.3.1 Raw material preparation and formulation of the puree mix

3.3.1.1 Keitt Mango variety

First, 20 kg of Keitt variety mango fruits were bought. The mangos were then brought to AAU, Food Engineering laboratory, washed thoroughly and pureed with a food processor. Thereafter 700ml of mango puree was taken for a nutritional composition analysis at Ethiopian Health and Nutrition Research Institute (EHNRI) in the Food Science and Nutrition Directorate Laboratory. The sample was tested for the contents of the protein, fat, moisture, fiber, ash, carbohydrate and Vitamin C which were believed to be significant for the research.

Two kilograms of honey was bought from Gojam area and processed traditionally at home for the purpose of mixing and development of the puree mixture as a sweetener. After the mango was pureed and mixed with lemon juice, honey and ground ginger in duplicate samples for proximate analysis so as to compare the effect of the ingredients on the nutritional composition and physicochemical qualities.

3.3.1.2 Tommy Atkins variety

Tommy Atkins variety of 20kg Mango fruits were washed thoroughly and pureed with a food processor. 700ml of mango puree was taken for a nutritional composition analysis at Ethiopian Health and Nutrition Research Institute (EHNRI) in the Food Science and Nutrition Directorate Laboratory. The sample was tested for the contents of protein, fat, moisture, fiber, ash, carbohydrate and Vitamin C with the same procedure used for the Keitt variety.

3.3.1.3 Making fresh Mango puree

The puree was made using a food grinder immediately after the fruits are peeled and de-stoned to avoid excessive browning. This food processor with appropriate speed was chosen because the normal fruit blending machine (mixer) was not able to mix the puree properly since water was not added during the process. The puree was weighed to be 1.65 kg. Then the puree was placed and covered in a water bath fitted with thermostat to control the temperature and blanched at low temperature at 600C over boiling water for 10 minutes. This helped for preserving the natural fruit flavor and light color and also to inactivate the enzymes. The pulp was then strained through a screen to remove any peels and other unnecessary materials which were not properly handled before, to obtain a pure puree.

3.3.1.4 Preserving the Mango color

Since light-color fruit leathers tend to darken during drying, the color of the mango leather was preserved by adding citric acid. Lemon juice was used in the laboratory instead of crystal or tablet form of ascorbic acid. This was done by addition of 0.03kg of lemon juice per 1.65 kg of mango puree. The puree was sweetened by adding 0.065kg of pure honey. Honey was chosen as sweetener instead of sugar to prevent formation of crystals at the end of drying the leather. Honey resulted in relatively stickier mango leather.

3.3.2 Heating and drying the puree mix

The juicy puree was heated to cook and shorten the drying time and also save energy. This was done by placing the ground or pureed mango puree in a hot water bath fitted with thermostat (Model: GP 200, Grant) and a stirrer at a water temperature of 84 0C until the temperature of the puree reaches 750C while continuously stirred. The puree was cooked over low heat by constantly stirring until the mixture thickens. The total time required for the cooking process was two hours.

The puree was poured and leveled with approximately 0.4 and 0.6g/cm2 puree load on three aluminum shield trays which were greased with edible corn oil to prevent sticking on the final leather. Thereafter, 750mg of ground ginger spice was added on the surface of puree in each tray for flavoring. The trays were placed in the oven with 7.32cm clearance from the top and the bottom of the trays. The temperature was adjusted between 60 and 800C and drying continued for 10 h. The dryness of the leather had been regularly inspected during the drying period. The trays had been turned and rotated in every hour during the drying time. The dryness of the mango leather was checked by slightly touching with fingers without putting any finger print until the stickiness of the leather stopped. It took totally 10 h to get the final leather product by using drying oven. Test for doneness of the process was also carried out by front teeth, and the final mango leather was felt tacky being slightly sticky to the mouth with very low moisture content. Finally, the weight of the mango leathers in each tray was determined and the total weight of the product was calculated. The general process flowchart for making fruit leather is indicated in figure 3.1 below.

Fully Ripened Mangos

Sorting

Washing

Peeling

Cutting

Pulping

Crushing

Mixing

Heating (60, 70 and 800C) for 2 h

Removal of foam

Pour the hot puree on to the trays

Convective drying (60, 70, and 800C) for 4-10 h

Packaging with plastic bags

Labeling

Storage in a cool and dry place

Figure 3.1 Process flowchart for Mango leather processing

3.4 Methods for studying the effect of processing

Drying was conducted according to a central composite design with two independent variables: drying temperature (60, 70, and 800C) and puree load (puree mass per dish area, 0.4–0.6 g/cm2) according to Azeredo (2006). The ranges of the variables were determined from preliminary tests. The experimental design was carried out to compare the effects of processing on the qualities of both varieties of mango fruit leather and suggest the optimum conditions and the minimum time required for the leathers to achieve a moisture content of 15–18%. Triplicate samples were taken at 15 min intervals for 2 h and submitted for moisture content determination. The product obtained under the optimum conditions was finally submitted to evaluation of the quality parameters including sensory analyses.

3.4.1 Effect of processing on drying time

3.4.1.1 Drying experiment using convective dryer

The experiment was conducted using a convective dryer in AAU Food Engineering Laboratory to determine the influence of drying air temperature and puree load on drying time of mango fruit leather. The dryer consists of a drying chamber, electrical heater, blower and temperature controller (20 to 80°C, dry bulb temperature). During the experiment, the drying air velocity was set at 0.5 m/s and the relative humidity of the air was 65±1%. The puree load of 0.4, 0.5, 0.6g/cm2 were uniformly spread in square stainless steel meshed tray sheeted with aluminum foil.

The convective dryer was switched on at the beginning of each test and the required temperature was set. When the dryer reached the steady state condition, the mango puree samples were uniformly spread in square stainless steel meshed trays size (10cm X 10cm) covered with aluminum foil and kept in the drying chamber of the dryer. Air flow was parallel to the surface of the Mango puree. The drying was continued until the moisture content of the samples dropped to 15 to 18% (Azeredo et al., 2006).

The moisture content of the dried samples was measured by placing the samples at 105°C in MB45 Moisture Analyzer. More than 1g of sample was taken for each analysis of the product from both mango varieties treated with different temperatures and puree load. Determination of the moisture content was done in triplicate.

3.5 Quality parameters for studying the effect of processing

The effect of processing during development of mango fruit leathers was studied by analyzing the moisture loss and the texture of the final product, conducting proximate analysis, physico-chemical analysis and sensory evaluation. The influence of temperature and the puree load on the drying dishes was also studied to find out how the drying process affects the qualities of the mango fruit leather and how long will it take to dry the fruit leather.

3.5.1 Proximate analysis methods for the puree and leather

The proximate analysis was conducted at Ethiopian Health and Nutrition Research Institute (EHNRI), and all the moisture content, protein, fat, crude fiber, carbohydrate and ash were determined according to AOAC methods. All of the chemicals and reagents used for the analysis of the mango puree, puree mix and the final fruit leather were supplied by the Food Laboratory of EHNRI.

3.5.1.1 Moisture determination

The amount of water present in the mango sample was considered to be equal to the loss of weight after drying the sample to constant weight at a temperature of 100oC according to Method AOAC (2003).

Formula:

W *100 %Moisture  2 W1

W *100 %Totalsolids  3 W1

Where: W1 ,W2 andW3 are in wet base.

W1 = weight of wet sample

W2 = loss of weight

W3 = weight of dry sample

3.5.1.2 Crude fiber 38

The crude fiber content of the Mango sample was analyzed according to Method AOAC (2003); a fat-free or low fat content sample is treated with boiling sulfuric acid and subsequently with boiling potassium hydroxide or sodium hydroxide, the residue after subtraction of the ash is regarded as fiber.

Formula:

W W 100  M  Crude fiber g /100g  1 2 W3

Where: W1 = Crucible weight before drying (g)

W2 = Crucible weight after drying (g)

W3 = Sample dry weigh (g)

M = Moisture content of the sample (%)

3.5.1.3 Crude protein

The crude protein content of the Mango sample was analyzed according to Method AOAC (1984); all nitrogen is converted to ammonia by digestion with a mixture of concentrated sulfuric acid and concentrated orthophosphoric acid containing potassium sulfate as a boiling point raising agent and selenium as a catalyst. The ammonia released after alkalinization with sodium hydroxide is steam distilled into boric acid and titrated with sulfuric acid.

Formula:

mg nitrogen T  B * N *14

mg ofnitrogen*100 g nitrogen /100 g sample  mg sample

T  B* N *1.4 Total nitrogen%  *100 W

Crude Protein = total nitrogen (%) * 5.78

Where: T = volume of sulfuric acid solution used in the titration of test materials.

B=Volume of sulfuric acid solution used in the titration for the blank.

N = normality of the acid

14 = Eq. wt of nitrogen

W = wt. of the sample

3.5.1.4 Fat content

The fat content of the Mango sample was analyzed according to Method AOAC (1984); fat is extracted with ether (peroxide free) from dried samples in a soxhlet apparatus, and the other is evaporated from the extraction flask. The amount of fat is calculated from the difference in weight of the extraction flask before and after extraction.

Formula:

W W2 W1

W * 100  %moisture Fat g /100g fresh sample  WD

Where: W= weight of fat (g)

W2 = weight of extraction flask after extraction (g)

W1 = weight of extraction flask before extraction (g)

WD = weight of dried sample (g)

3.5.1.5 Ash content

The organic matter is burned off at low temperature and the inorganic materials remaining are cooled and weighed. Heating is carried out in stages, first to derive the water, then to char the product thoroughly and finally to ash at 550oC in a muffle furnace (AOAC, 1984).

Formula:

W *100 % Ash  2 W1

Where: W1 = weight of sample W2 = weight of ash

3.5.1.6 Carbohydrates

The total carbohydrate contents of the mango sample (C %) by mass including crude fiber can be obtained as follows:

Formula:

C% 100  P  F  A  M

Where: P – The mass percent of protein

F – The mass percent of fat

A – The mass percent of ash

M – Moisture content (%)

Therefore, the Utilizable Carbohydrate (CHO) = Total CHO – Crude fiber

3.5.2 Physicochemical analysis

The physico-chemical analysis for the mango puree (including: pH, moisture content, and viscosity) was undertaken at AAU Chemical Engineering laboratory. The pH was measured using pH meter. The TSS was measured by hand refractometer, titrable acidity was determined by titration method, °Brix /acidity ratio was calculated and the vitamin C content was also measured using Spectrophotometric method at EHNRI.

3.5.2.1 Determination of viscosity of the Mango puree

The viscosity of the puree was measured by Vibro viscometer (SV-10, JAPAN), (2001) model which works between 0.3 and 10,000 mPa.s at different temperatures during the heating process on continuous mixing. Mango puree sample was poured into the cup until viscosity surface reaches between the level gauges. The level gauge indicates between 35 and 45ml. The cup was then

attached on the table along the guides, gently lowering the sensor plates above the sample surface and the viscosity was measured.

3.5.2.2 Determination of Vitamin C (Total Ascorbic acid) content

The vitamin C content of the mango fruit puree and leather were determined as to the laboratory manual of EHNRI Food Chemistry Laboratory using Spectrophotometric method. The reagents

used were deionized water, 9NH2SO4, 85% H2SO4, 5% meta phosphoric acid, HPO3, H3PO4, 2%

2.4-DHPH in 100 ml of 9N H2SO4, 2% Thiourea, saturated bromine solution, 6% Trichloroacetic acid and ascorbic acid standard. The apparatus used were: Grinder, Centrifuge, Filtration apparatus (funnel, vacuum pump, and filter paper), pipette, test tubes, volumetric flasks, Erlenmeyer flasks (250 ml), water bath apparatus and ice bath, and UV-Vis Spectrophotometer.

The procedure used for the determination of the Vitamin C content of the mango fruit leather includes: extraction, oxidation to Dehydroascorbic acid, formation of Osazone, formation of

soluble pigments (Treatment with 85% H2SO4), measurement of Color, and development of standard curve.

The calculation to o

btain the vitamin C content of the fruit leather was done using the following formula:

A(sample) - A(blank) Mg ascorbic acid/100g  A(10 µg std) - A(blank)

Where, A(sample) = Absorbance of the sample

A(blank) = Absorbance of the blank

A(10 µg std) = Absorbance of 10 µg standard

3.5.3 Texture analysis of the Mango leather

Texture analysis was done in the Food Engineering laboratory using Texture Analyzer (Model: TA-Plus, LLOYD instrument, England). The software used for analysis of the texture was NEXYGEN Plus. For this laboratory experiment, Volodkevitch bite test was used. This test was designed to imitate incisor teeth sharing through a food sample. The set comprises upper and lower “teeth” which during the test, are brought together until nearly touching. The samples were

positioned on the lower “tooth” and the results of the peak force required to bite through the samples was measured. A preliminary test was conducted for analysis of the textural characteristics of the Keitt mango fruit leather. The texture analyzer setting was kept at preload stress 7.3N, preload stress speed of 21mm/min and a test speed of 100 mm/min. The height of the mango leather sample was set at 5mm, the width was 10mm and the area was 50mm2 for each analysis. The experiment was conducted for different layers of mango leathers to find out how much layers of mango leathers could be suitable for biting. This compression test simulates the evaluation of toughness by consumer for a single bite of the mango leather. The absolute peak force from the resulting curve was considered as the amount of force required to compress the mango leather with front teeth. The maximum shear force required for cutting the mango leather was taken as the texture index of the dried product. The force-displacement and energy used for cutting the leather was recorded (Pushpa, 2006).

3.5.4 Microbiological analysis

The microbiological analysis was conducted at EHNRI for two samples selected from the final products of both mango varieties which were treated at 600C temperature and 0.6g/cm2 puree load. They were selected on the basis that microorganisms grow as the drying temperature was lower and the puree load was greater in relation to the other developed products.

Determination of Mold and Yeast was conducted using NMKL, No. 98, 1997 method (Annex 1). Aerobic Plate Count (APC) was determined as to NMKL, No. 86, 2006 (Annex 2). Coliform count was carried out according to NMKL, No. 44, 2004 (Annex 3). Fecal coliform count and E. coli was determined by FDA/BAM, 2006 (Annex 4). Determination of S. aureus count and B. cereus was done using NMKL, No. 66, 2003 (Annex 5). Isolation of Salmonella, Shigella, and Stapylococcus spp. was carried out by NMKL, No. 71, 2005 (Annex 6).

3.5.5 Sensory evaluation

The sensory tests were conducted with 20 panelists. The panelists were asked to give their individual ratings on all the leather characteristics including color, aroma, taste, flavor, toughness and overall acceptability of the Mango leather. A 9-point structured hedonic scale (1 – ‘extremely disliked’ to 9 – ‘extremely liked’) was used to conduct the preference test.

3.6 Experimental design and data analysis

A factorial arrangement in a completely randomized design was set to see the effects of processing on the qualities of both varieties of mango fruit leather and suggest the optimum conditions and the minimum time required for the leathers to achieve a moisture content of 15–18%. The experiment was undertaken to establish the optimum variables required to achieve the best product characteristics.

The experiment was repeated two times in duplicate samples. Two independent variables were selected for both varieties of mango fruit:

1. Drying temperature (60 to 80 0C)

2. Puree load (puree mass per dish area, which was in the range of 0.4 to 0.6g/cm2, (Azeredo et al., 2006).

Analysis of variance was done and level of significance was set at 5%. The data obtained was statistically analyzed by using Statistical Package for Social Scientists (SPSS 17th Version).

CHAPTER 4

RESULTS AND DISCUSSION

4.1 Physicochemical properties of Mango puree

The preliminary test results of the physico-chemical analysis of the mango pulp for both varieties of fruits are presented in Table 4.1. The selected physico-chemical parameters which may influence the quality of mango fruit leather were pulp moisture content, TSS, pH, acidity, °Brix /acidity and the vitamin C content.

Table 4.1 Physico-chemical properties of fruit pulp for the mango varieties

Variety Moisture TSS pH Acidity Brix/Acid Vitamin C (%) 0Brix g/100g Ratio (mg/100g)

Keitt 83.42 16.34 4.10 0.25 65.36 47.77

Tommy 85.33 17.23 4.60 0.19 90.68 29.91 Atkins

The results measured in the preliminary study indicated in the Table shows that the TSS, pH, titrable acidity are within the range for chemical composition of common ripe mango cultivars grown in different countries (Doreyappa & Ramannjaneya, 1995). The report indicates that the composition and properties of ripe mango range: TSS (14.60-22.27°Brix), pH (3.80-4.90), acidity (0.11-0.55 %) and total sugars (9.28-20.90%). They stated that the physico-chemical characteristics of fruits and the technological qualities of the products processed vary with the variety of the fruit. Some varieties are most suitable for specific application. The TSS of Keitt mango puree was less than that of Tommy Atkins, whereas the titrable acidity and vitamin C content of the Keitt mango puree were greater than that of the Tommy Atkins.

(palmer, keitt, Ameliorel and mango) were studied (Germain et al., 2003). It was mentioned that a pulp extracted from ripe fruit of the stated cultivars has a pH range of 3.91-4.35. Rameshwar (1993) stated that mango is considered to be matured when the total soluble solids, a measure of sweetness, reach 8° Brix. Kalra et al. (1995) also pointed out that harvesting is usually initiated when a few mango fruits on the tree begin to ripen and fall. Optimum maturity stage lead to uniform ripening and better storage life of about 1 week at 35 ± 0.1°C and 65 ± 1% RH ( Jha et al., 2004).

4.2 Proximate analysis results of the Mango puree and puree mix

The proximate analysis result for both varieties of mango puree and puree mix is presented on table 4.2 below.

Table 4.2 Proximate analysis result for Keitt and Tommy Atkins varieties of Mango puree and puree mix

Sample Type

Mango Puree Mixed Mango Puree + Honey +

Component Lemon Juice

Keitt Tommy Atkins Keitt Tommy Atkins

Moisture (%) 83.42 85.33 78.92 78.81

Fat (%) 0.65 0.16 0.83 0.22

Protein (%) 0.50 0.44 0.56 0.44

Ash (%) 0.30 0.36 0.37 0.37

Crude Fiber (%) 0.54 1.68 0.92 1.68

Carbohydrate (%) 14.59 12.03 18.4 18.48

Vitamin C (mg/100g) 47.77 29.91 53.85 44.64

4.2.1 Keitt Mango variety

Generally the proximate analysis result shows that there is an increase in nutritional content of the mango puree after enriched with the honey and lemon juice. Besides a decrease in moisture content has also observed which is suitable for drying purpose with less removal of moisture from the puree mix.

4.2.2 Tommy Atkins variety

The result shows that there is a decrease in moisture content of the puree mix and an increase in fat, protein and ash, and carbohydrate contents. The ash remained constant. The vitamin C content has also increased possibly due to the effect of the addition of the lemon juice. Therefore, mixing of the Tommy atkins mango puree with honey, lemon juice and ground ginger generally increased the nutritional content.

4.3 Effect of heating temperature on the viscosity of Mango puree mix

According to the study, the effect of temperature on the viscosity of the puree mix for both verities of mangoes was determined in 1.5h period and the results are discussed below.

Table 4.3 Results of viscosities for Keitt and Tommy Atkins variety mango puree mixes measured at different heating temperature

Keitt Tommy Atkins

Temperature (0C) Viscosity (m.pa.s) Temperature (0C) Viscosity (m.pa.s)

25.1 964 25.1 510

30.0 955 30.3 485

35.3 948 35.0 443

40.2 913 40.1 426

45.0 869 45.2 414

50.1 818 50.0 401

55.3 797 55.3 393

60.7 791 60.2 405

63.9 804 65.1 555

65.0 820 67.0 625

68.1 841 68.1 676

69.0 845 - -

70.0 915 - -

4.3.1 Keitt Mango variety

These results can easily be graphically illustrated below in Figure 4.1.

Figure 4.1 Viscosity verses temperature of Keitt variety puree mix

The result generally showed the decrease in viscosity at the beginning from 964m.pa.s to 791m.pa.s at different treatment temperatures. Then at 63.90C, the viscosity of the puree mix started to rise to 804m.pa.s and increased afterwards up to 915m.pa.s at 70.00C. At the final measured viscosity, the puree mix was found cooked and the odor was a bit changed. So, the measured puree was finally decided to be out of the water bath and became ready for the next drying process. From the result of the laboratory experiment it can be concluded that the viscosity of mango puree is temperature dependent. As the temperature increases, the viscosity of the puree first decreases and then it increases within the temperature range of 25.1 to 70.0 0C.

4.3.2 Tommy Atkins variety

These results can easily be graphically illustrated below in Figure 4.2.

Visco. Temperature Vs Viscosity (m.pa.s) 800

700

600

500

400

300

200

100

Figure 4.2 Viscosity verses temperature of Tommy Atkins variety puree mix

The result indicated that a decrease in viscosity at the beginning from 510m.pa.s to 393m.pa.s at different treatment temperatures. At 60.20C, the viscosity of the puree mix started to rise to 405m.pa.s and increased afterwards up to 676m.pa.s at 68.10C. Finally, the puree mix was found cooked and the odor was changed. So, the measured puree was finally decided to be out of the water bath and became ready for the next drying process. This shows that the viscosity of mango puree is also temperature dependent. As the temperature increases, the viscosity of the puree first decreases and increases within the range of 25.10C to 68.1 0C. From the experiment, it has been found that the viscosity of the Tommy Atkins mango puree mix is generally lower than that of the Keitt variety mango puree mix.

4.4 pH of the puree mix

The pH of the Keitt variety puree mix on average was 4.1 and that of the Tommy Atkins puree mix was 4.6. With the addition of citric acid, lemon juice was added to bring the pH of the mango puree mix down to 3.9 to make it safe for microbial effects.

4.5 Effect of drying on the proximate and Vitamin C content of fruit leather

After the mango puree was dried with the combination of different drying temperature and puree load for both mango varieties, the fruit leather was subjected to nutritional composition analysis in Ethiopian Health and Nutrition Research institute (EHNRI). The laboratory analysis result is presented in Table 4.4 below.

Table 4.4 Proximate analysis result for Mango fruit leathers

Sample Code

Component A B C D E F G H I J K L M N

Moisture (%) 16.25 19.36 15.59 17.12 15.64 18.76 14.86 15.96 14.42 13.21 14.57 15.13 13.69 14.89

Fat (%) 1.98 2.27 4.68 1.61 2.23 1.99 3.55 1.76 2.47 2.85 4.12 0.95 0.33 0.19

Protein (%) 2.21 1.75 2.20 2.27 2.81 2.47 2.59 2.44 2.46 2.76 2.31 2.09 2.30 2.26

Ash (%) 1.84 1.41 2.04 1.89 2.19 1.93 2.29 2.10 1.66 2.16 2.29 2.08 1.52 1.94

Crude Fiber 6.52 5.14 5.77 7.41 7.11 7.97 7.37 6.70 5.57 6.87 5.00 4.59 4.02 5.34 (%)

Carbohydrate 71.2 70.07 69.72 69.70 70.02 66.88 69.34 71.04 73.42 72.15 71.71 75.16 78.14 74.66 (%)

Vitamin C 44.44 30.88 23.57 22.91 31.91 23.76 23.08 15.59 15.70 14.98 33.95 17.19 23.61 33.92 (mg/100g)

Where, the sample codes were designed for both varieties of mango with drying temperature and puree load as:

Table 4.5 Designed sample codes for both varieties of mangos with drying temperature and puree load

Keitt Tommy Atkins

Temperature (0C) 0.4g/cm2 0.6 g/cm2 0.4 g/cm2 0.6 g/cm2

60 A B C D

70 E F G H

80 I J K L

Code “M” and “N” is product samples experimented with convective hot air dryer for comparison of the effect of processing using drying oven. Product “M” was developed at 700C with 0.6 g/cm2 puree load from Keitt mango variety where as product “N” was developed from Tommy Atkins Mango with the same condition.

4.6 Effect of temperature and puree load on drying time

4.6.1 Drying characteristics of Mango puree mix

The effect of drying air temperature and puree load on drying time taken to reach the final moisture content (15 to 18%) is presented in Table 4.6. The drying time was generally shorter at higher temperatures due to quick removal of moisture. The puree load also affected the drying time at all drying temperatures. Drying time was considerably prolonged for more than 7 hrs for 0.6g/cm2 puree at all drying air temperatures. Drying at higher temperature, 80°C reduced the required drying time by 42.9 %, 25% and 30 % for 0.4 g/cm2, 0.5 g/cm2, and 0.6 g/cm2 puree loads respectively.

Table 4.6. Effect of drying air temperature and puree load on drying time of Keitt Mango fruit leather

Drying Time of Mango Fruit Leather (h)

Drying Temperature (0C) 0.4 g/cm2 0.5 g/cm2 0.6g/cm2

60 7 8 10

70 6 7 8

80 4 6 7

The moisture content of the mango fruit leather was measured in every hour during the drying period until the final moisture content of the leather reaches 15% to 18%. More than 1g of sample was being taken for each analysis of the products from both mango varieties treated with different temperature and puree loads.

4.6.2 Analysis of moisture loss during drying process

The analysis of moisture loss of the leather after drying was determined and reported in Table 4.7. The result of the analysis showed 70.3% moisture loss after drying process is completed.

Table 4.7 Weights and moisture loss of Keitt variety mango leather

Mango and Mango Products Weight (kg)

Mangos 3.2

Puree before drying 1.75

Leather after drying 0.52

% Moisture Loss 70.3%

4.7 Texture analysis of the Mango leather

A preliminary test was conducted for analysis of the textural characteristics of the Keitt mango fruit leather. The measurement of texture of the mango leather product was believed to be significant in that it would be useful for correlating the toughness of the final mango leather product with that of the sensory analysis results. This could also be useful as a reference and for selecting the best product characteristics in terms of textural quality. The results are given in Table 4.8.

Table 4.8 Results of compression test using Texture Analyzer to different number of Mango leather sheets (layers)

Mango leather trials Thickness Extension Width with Different number of (mm) Limits (mm) Load (N) Time (s) sheets (mm)

Batch 1 (4 sheets) 5 4 10 2.4 2.9

Batch 2 (5 sheets) 6 5 10 22.9 3.5

Batch 3 (6 sheets) 7 6 10 Exceeds Limit 3.2

Batch 4 (6 sheets) 7 5 10 Exceeds Limit 3.0

Batch 5 (6 sheets) 7 4 10 3.4 3.5

It was observed that the load needed to compress (or to bite as a consumer’s teeth) for 6 sheets of mango fruit leather with 7mm thickness and extension limits of the texture analyzer’s probe set at 6mm and 5mm, exceeded the limit. Therefore, it is recommended that fruit leathers with 4 sheets and 5 sheets having 5mm and 6mm thickness respectively could be suitable for a single bite.

4.8 Proximate analysis of Mango fruit leather

Table 4.9 Effect of drying temperature on proximate composition of mango leather

Proximate composition

Temperature Moisture Protein Fat Fiber Ash Carbohydrate (0C) (%) (%) (%) (%) (%) (%)

60 17.080a 2.108a 2.637a 6.231a 1.728a 70.217a

70 16.305b 2.580b 2.381a 7.309b 2.127b 69.284b

80 14.333c 2.407c 2.597a 6.454c 2.048b 72.161c a-c Means bearing the same letters in the same column are not significantly different at P < 0.05

Table 4.10 Effect of puree load on proximate composition of mango leather

Proximate composition

Moisture Protein Fat Fiber Ash Carbohydrate

Puree Load (g/cm2) (%) (%) (%) (%) (%) (%)

0.4 15.222a 2.432a 3.171a 6.510a 2.052a 70.518a

0.6 16.590b 2.298b 1.906b 6.819b 1.884b 70.590a a-b Means bearing the same letters in the same column are not significantly different at P < 0.05

Table 4.11 Effect of fruit variety on proximate composition of mango leather

Proximate composition

Moisture Protein Fat Fiber Ash Carbohydrate

Mango Variety (%) (%) (%) (%) (%) (%)

Keitt 16.273a 2.411a 2.298a 6.626a 1.864a 70.518a

Tommy Atkins 15.538b 2.318b 2.778b 6.703b 2.071b 70.590a

a-b Means bearing the same letters in the same column are not significantly different at P < 0.05

4.8.1 Moisture content

The analysis shows that there is a significant difference (P < 0.05) between moisture content means of the mango leathers due to temperature, puree load and fruit variety. The average moisture content of the fruit leather is dependent on the drying temperature. As the drying temperature increases from 600C to 700C and then 800C, the average moisture content decreases to 17.08%, 16.31%, and 14.33% respectively (Table 4.9).

The results in Table 4.10 also indicate that the moisture content is dependent on the puree load. When the puree load was 0.4g/cm2, the moisture content was 15.22% and when the puree load increased to 0.6g/cm2, the moisture content of the leather has also increased to 16.59%.

On Table 4.11, it was indicated that the moisture content of the leather is also dependent on the mango varieties. The moisture content of the Keitt variety mango leather 16.27% was greater than the Tommy Atkins mango leather 15.53%. When compared to the fresh puree mix, the moisture content of the Keitt variety mango leather has decreased from 78.92 to 16.27 with 79.38% and that of Tommy Atkins from 78.81% to 15.53% with 79.24% because of the drying effect. According to Azeredo, et al., (2006) the average moisture content of mango fruit leather is in the range of 15% to 18%. Therefore, except for 14.33% average moisture content of the mango leather which was dried at 800C, the other fruit leathers have an average moisture contents within the mentioned range.

4.8.2 Protein content

From the analysis, a significant difference (P < 0.05) has been observed on the average protein content with all drying temperature, puree load and fruit variety. As indicated in Table 4.9, the average protein content of the fruit leather 2.58% was relatively higher at 700C drying temperature than that of at 600C and 800C which are 2.108% and 2.40% respectively. Table 4.10 also shows that there is an increase in average protein content with an increase in puree load. At 0.4g/cm2 puree load, the average protein content was 2.43% and at 0.6 g/cm2, it was 2.29%. The fruit variety has also an effect on the average protein content of the fruit leather. The mango leather from Keitt variety has an average protein of 2.41% and 2.31% for Tommy Atkins (Table 4.11). It has been observed that there is a difference in the average protein content with the mango variety of the puree mix, 0.56% for Keitt and 0.44% for Tommy Atkins in Table 4.2 and 4.3 respectively. However, the results show that the average protein content of the Keitt variety mango was greater than that of the Tommy Atkins for both puree mix and final leather.

4.8.3 Fat content

The mean fat contents of the fruit leathers were significantly different (P < 0.05) as they are affected by the fruit variety and the puree load. However, drying temperature didn’t have a significant effect on the fat content indicated on Table 4.9. In Table 4.10, it can be observed that when the puree load increases from 0.4 g/cm2 to 0.6g/cm2, the average fat content of the fruit leather decreases from 3.17% to 1.90% respectively. As indicated in Table 4.11, the Keitt variety fruit leather has an average fat content of 2.29% and that of Tommy Atkins is 2.77%.

4.8.4 Crude fiber content

The mean crude fibers of the mango fruit leathers were also significantly different from each other (P < 0.05). All drying temperature, puree load and fruit variety affected the composition. It was observed that the mean difference of the crude fiber for all drying temperature, was significantly different. As indicated in Table 4.9, at 700C drying temperature, the average fiber content 7.30% was relatively higher than that of the fiber contents 6.23% and 6.45% treated with 600C and 800C drying temperature respectively. In Table 4.10, it is indicated that as the puree load increases 0.4 gcm2 to 0.6gcm2 the average fiber content also increases 6.51% to 6.81%. It was observed that (Table 4.11), the Keitt mango leather has lower 6.62% crude fiber than the Tommy Atkins mango leather 6.70%. As indicated in Table 4.2 and 4.3, the Keitt mango puree mix has 0.92% which is lower than that of the Tommy Atkins (1.68%).

4.8.5 Ash content

With the exception of temperature, the ash content of the fruit leather was significantly affected (P < 0.05) by the puree load and the fruit variety. It was observed in Table 4.10 that the average ash content of the fruit leather decreased from 2.05% to 1.88% when the puree load increased 0.4 g/cm2 to 0.6g/cm2. As indicated in Table 4.11, the Keitt mango leather has an average ash content of 1.86% while Tommy Atkins mango leather has 2.07%.

4.8.6 Carbohydrate content

The analysis showed that drying temperature has a significant effect on the average carbohydrate content of the mango leather (P < 0.05) From Table 4.9, higher average carbohydrate content 72.161% was observed at 800C drying temperature in relation to that of 600C and 700C with 70.21% and 69.28% respectively. Both the puree load and the fruit variety did not have a significant effect on the carbohydrate content.

4.8.7 Effect of processing on Vitamin C content of Mango leather

Vitamin C (L-ascorbic acid) is the least stable of all vitamins and will easily be destroyed during processing and storage. Exposure to oxygen and light and prolonged heating in the presence of oxygen during processing will decrease the vitamin C content of foods (Fennema, 1996).

Table 4.12 Effect of drying temperature, puree load and fruit variety on vitamin C content

Factors Vitamin C (%)

60 30.446a

Temp. (0C) 70 23.585b

80 20.445c

Puree Load (g/cm2) 0.4 28.773d

0.6 20.877e

Variety Keitt 26.937f

Tommy Atkins 22.714g

a-g Means bearing different letters in the same column are significantly different at P < 0.05

The average vitamin C content of the fruit leather was significantly affected (P < 0.05) by all the drying temperature, puree load and fruit variety. A significant effect on the average vitamin C content of the fruit leather was observed for all drying temperatures 600C, 700C, and 800C. When the drying temperature and puree load increased, the average vitamin C content decreased. The average vitamin C content of the fruit leather was also dependent on the fruit variety. The vitamin C content of the Keitt mango leather (26.93%) is greater than that of Tommy Atkins mango leather 59

(22.71%). When compared to the fresh puree mix, the Keitt mango leather is decreased by 39.66% from 44.64% to 26.93% and the Tommy Atkins mango leather is decreased by 57.82% from 53.85% to 22.71%.

4.9 Microbiological analysis of Mango fruit leather

The result of the microbiological analysis for the two fruit leather is given in Table 4.13

Table 4.13 Result of microbiological analysis of mango fruit leather

Result for Samples (cfu/g)

2 0 2 0 Parameters (Tests) B2 (0.6g/cm ) at 60 C D2 (0.6g/cm ) at 60 C

Mold count at 250C/5-7 days 6X104 5X102

Yeast count at 220C/5-7 days 1X104 <1X101

APC at 300C/72 h 1X105 1.02X105

Coliform count <1X101 <1X101

Fecal coliform count <1X101 <1X101

E.coli count <1X101 <1X101

S.coccus spp Not isolated/25g Not isolated/25g

Salmonella spp Not isolated/25g Not isolated/25g

Shigella spp <1X104 5.2X103

i.e. APC = Aerobic bacteria plate count

0 2 Product B2 is Keitt mango leather developed at 60 C and 0.6g/cm puree load where as product D2 is Tommy Atkins mango leather developed at 600C and 0.6g/cm2 puree load.

In the counts < 1 X 101 is the standard reporting format for plates from all dilution of the sample has no colonies. The microbiological result for yeast, coliform, fecal coliform, E. coli counts and Shigella species for both varieties of mango leathers was found to be safe < 1 X 104. S.coccus and 60

Salmonella species were not isolated for both products. The mold and aerobic bacterial plate counts were found to be higher. This could be as a result of unhygienic condition during the process of the product development. However, the product had been subjected to sensory analysis and there was no harm in any of the panelists which indicates that there is no significant effect on health.

4.10 Sensory analysis of Mango fruit leather

4.10.1 Effect of drying temperature, puree load and fruit varieties on the sensory qualities

Table 4.14 Effect of drying temperature on sensory qualities

Sensory qualities

Overall acceptability Temperature Color Aroma Taste Flavor Toughness (0C)

60 7.388a 6.988a 7.012a 7.013a 6.300a 7.175a

70 7.075a 6.763a 7.088a 6.763a 6.125a 6.838a

80 6.788a 6.687a 6.813a 6.825a 5.462b 6.475b

a-b Means bearing the same letters in the same column are not significantly different at P < 0.05

Table 4.15 Effect of puree load on sensory qualities

Sensory qualities

Overall acceptability Puree Load Color Aroma Taste Flavor Toughness (g/cm2)

0.4 6.983a 6.775a 6.817a 6.742a 5.525a 6.575a

0.6 7.183a 6.850a 7.125a 6.992a 6.400b 7.083b

a-b Means bearing the same letters in the same column are not significantly different at P < 0.05 61

Table 4. 16 Effect of fruit variety on sensory qualities

Sensory qualities

Mango Variety Overall acceptability

Color Aroma Taste Flavor Toughness

Keitt 6.083a 6.475a 6.600a 6.483a 5.508a 6.250a

Tommy Atkins 8.083b 7.150b 7.342b 7.250b 6.417b 7.408b

a-b Means bearing the same letters in the same column are not significantly different at P < 0.05

4.9.1.1 Color

Color is one of the quality parameters of fruit leathers. The color of the fruit leather was significantly affected (P < 0.05) only by the fruit variety. On average, the color of the fruit leather dried at 600C and 700Cwas liked moderately by the respondents and the other which was dried at 800C was preferred slightly (Table 4.14). Moreover, the color of the fruit leather dried at 0.4 g/cm2 and 0.6 g/cm2 was approximately liked moderately by the respondents (Table 4.16). The respondents also liked very much the Tommy Atkins fruit leather, whereas for Keitt mango fruit leather, it was only slightly liked. Therefore, the Tommy Atkins Variety mango fruit leather was relatively of good quality based on the panelists’ preference. The color difference between the two mango varieties is shown in the pictures below.

Pic. 4 Tommy Atkins Mango fruit leather

Pic. 5 Keitt Mango fruit leather

4.9.1.2 Aroma

The aroma of the mango fruit leather is another quality parameter to grade the final products. From the sensory analysis result, it was observed that the aroma of the fruit leather was significantly affected (P < 0.05) by the mango variety. The drying temperature and the puree load did not have significance effect on the aroma. Table 4.14 and 4.15 indicate that the color of the fruit leather dried at all temperatures 600C, 700C, and 800C and puree load respectively was moderately liked by the respondents having a value of 7. Table 4.16 shows that the aroma of the Tommy Atkins mango fruit leather was liked moderately and that of the Keitt variety was slightly liked. Therefore, based on the panelists’ preference, the Tommy Atkins mango fruit leather had relatively a better aroma than that of the Keitt variety.

4.9.1.3 Taste

The taste of the mango fruit leather was not significantly affected (P < 0.05) by the drying temperature and the puree load. Table 4.14 and 4.15 show that the taste of the fruit leather was liked moderately by the respondents on average. However, the taste of the fruit leather was significantly affected by the fruit variety. Table 4.16 indicates that the Keitt variety mango fruit leather was liked slightly by the respondents, where as the Tommy Atkins fruit leather was liked very much. Therefore, it can be concluded that the taste of the Tommy Atkins mango leather had a better quality in terms of taste.

4.9.1.4 Flavor

The flavor of the mango fruit leather was not significantly affected (P < 0.05) by the drying temperature and the puree load. In Table 4.14 and 4.15, it is indicated that the flavor of the fruit leather was moderately liked by the respondents approximately. However, the flavor of the fruit leather was significantly affected by the variety of the mango fruit. Table 4.16 indicates that the flavor of the Keitt fruit leather was slightly liked, where as the flavor of the Tommy Atkins fruit leather was moderately liked by the respondents. Therefore, based on the panelists’ preference, the flavor of the Tommy Atkins fruit leather was relatively of good quality. Heat not only vaporizes water during drying but also causes loss of volatile components from the food and as a result most dried foods have fewer flavors than the original material. The extent of volatile loss depends on the temperature and moisture content of the food and on the vapor pressure of the volatiles and their solubility in water vapor. Volatiles which have a high relative volatility and diffusivity are lost at an early stage in drying. Foods that have a high economic value due to their characteristic flavors (for example herbs and spices) are dried at low temperatures (Mazza and LeMaguer, 1980).

4.9.1.5 Toughness

The toughness of the fruit leather is another quality parameter for grading fruit leathers. From the sensory analysis result, it was observed that the toughness was significantly affected (P < 0.05) by all the drying temperature, puree load and the fruit variety. The drying temperature has a significant effect on the toughness of the fruit leather especially at 600C and 800C and at 700C and 800C and their interactions. Table 4.14 indicates that the toughness of the fruit leather dried at 600C and 700C was slightly liked, whereas the toughness of the fruit leather dried at 800C was neither liked nor disliked by the respondents. A decrease in toughness was also observed with an increase of the

drying temperature. The toughness of the fruit leather dried with 0.4g/cm2 puree load as in Table 4.15 was neither liked nor disliked where as the one with 0.6 g/cm2 was slightly liked by the respondents. An increase in toughness with an increase of the puree load was also observed.

As indicated in Table 4.16 on average, the Keitt mango leather was neither liked nor disliked whereas that of the Tommy Atkins mango leather was slightly liked by the respondents. Additionally, 25% of the panelists suggested that the toughness of the fruit leather shall be softer. Since fruit leathers are not common in Ethiopia, the respondents find the product harder than an ideal or their expectations. Therefore, according to the panelists’ result, the Tommy Atkins mango leather dried at 60 0C or 700C with 0.6 g/cm2 is considered to be of better quality mango fruit leather in terms of toughness.

4.9.1.6 Overall acceptability

The overall acceptability of mango fruit leather was significantly affected (P < 0.05) by all the drying temperature, puree load and fruit variety. There is a significant effect on overall acceptability due to drying temperature at 600C and 800C. The overall acceptability of the mango leathers decreases with an increase of temperature Table 4.14. It has been also observed that the overall acceptability of the fruit leather dried at 600C and 700C was moderately liked by the respondents, whereas the fruit leather dried at 800C was only slightly liked.

The overall acceptability of the fruit leather with 0.4 g/cm2 and 0.6 g/cm2 puree load was moderately liked by the respondents. Table 4.16 indicates that the overall acceptability of the Keitt mango leather was liked slightly, whereas the Tommy Atkins mango leather was moderately liked. Therefore, according to the panelists’ preference, the Tommy Atkins mango fruit leather dried at 600C and 700C with both puree loads 0.4 g/cm2 and 0.6 g/cm2 is considered to be the best leather in terms of overall acceptability.

CHAPTER 5

SUGGESTED TYECHNOLOGY FOR MANGO LEATHER PROCESSING

5.1 Process description

Mango fruits can be processed and preserved in leather form. This can easily be achieved at a small scale industry through the following process procedures. First, the preliminary operations including: washing, sorting, peeling, cutting (slicing) and blanching will be done and then mixing, concentrating and drying will follow and finally, packaging, labeling and storage will make the process complete. Processing the mango fruits is intended to preserve them by slowing down the natural processes of decay caused by microorganisms, enzymes in the food, or other factors such as heat, moisture and sunlight and to change them into mango leather form, which are attractive and in demand by consumers. The processors should use their skills to develop attractive recipes and make mango leathers that consumers want to eat. By doing this successfully, they can increase sales and earn an income.

Preliminary plant design is suggested for small scale local mango fruit (Keitt Variety) leather processing industry in Ethiopia. This was done with the consideration of the availability of the mango fruit with in the country throughout the year as well as the low price of the incoming raw mango fruits to the processing industry. However, from the sensory analysis, it was observed that most of the consumers’ preference is towards Tommy Atkins fruit leather having a higher sensory quality. As a beginning, the researcher believes that a small scale plant design shall be suggested for processing locally grown mango fruits as the product could be relatively expensive. Moreover, with the same plant design if implemented with a lower capital investment, it would also be suitable for processing of the export standard Tommy Atkins mango fruits whenever there is plenty supply because the fruit is very seasonal. The following flow sheet (Figure. 4.3) clearly describes the process for making mango leathers for small scale processing industry.

Mangos

Reception and Storage

Preliminary Washing

Sorting and Grading

Secondary Washing

Weighing

Peel + Caustic Hot Caustic Peeling Soda Soda Slurry

De‐stoning (Pulping) Stones

Pulp

Blanching

Honey + Mixing Spices Citric Acid

Puree

Concentrating

Drying

Packaging

Mango Leather

Fig. 4.3 Qualitative flow diagram for Mango leather processing

 Material and Energy Balances

Material balance as per laboratory work:

The material balance will enable us to quantify the substances going in and out of the entire process and piece of equipments. Emissions can be calculated as the difference between the input and output of each listed substances. If there is any accumulation within the equipment during process, it should be accounted for the calculation.

Literature Data:

A survey of the literature will often reveal general information and specific data pertinent to the development of a design project. The literature data for physicochemical and composition of mango and mango puree is summarized in Table 4.17.

Table 4.17 Proximate and physicochemical composition of Mango and puree

Value Ranges (% Fresh Weight)

Composition Mango Fruit Mango Puree

Moisture 72.1–85.5 67–86

Crude protein 0.30–5.42 0.3–1.5

Crude fiber 0.30–2.38 0.05–0.6

Ash 0.29–1.13 0.13–0.61

Total soluble solids 17–24 0.28–0.64

Total sugars 10.5–18.5 12.28–17.54

pH 4.0–5.6 11.27–15.38

TA (as citric) 0.327 0.1–1.1

Source: Hulme (1971), Caygill et al. (1976), Wu et al. (1993), and Narain et al. (1998).

The literature data for average compositions of Honey is summarized below:

 Moisture Content (M.C) = 17.1%

 Carbohydrate = 82.4%

 Proteins, amino acids, vitamins, and minerals = 0.5%

Source: National Honey Board (2009).

The literature data for average composition of lemon juice is:

 Moisture content = 92%

 Solids = 8%

For Lemon Fruit, the average values per 100g of edible portion are:

 Water = 89g

 Protein = 1.10g

 Fat = 0.30g

 Carbohydrate = 9.32g

 Fiber = 2.8g

Source: USDA National Nutrient Database (2004), within the Handbook of Fruits and Fruit Processing, Hui (2006).

Laboratory test result:

The laboratory data for the process of mango leather production provides information useful for a rapid material balance. This is summarized as follows:

 Mass of Mango fruits = 3,195g = 3.2 kg

 Mass of peel = 629.6g = 0.631kg

 Mass of Stones = 824.8g = 0.82kg

 Mass of Pulp = 1652.6g = 1.65kg 69

 Mass of mango leather = 520g = 0.52kg

 Mass of Honey = 65g

 Mass of Spices = 5g

 Mass of Lemon juice = 30g

 Drying time = 8 h

 Water temperature of the water bath = 800C

 Temperature of the puree = 750C

Assumptions:

Plant production capacity of 200 days per year

Production of 200kg of mango leather per day

Therefore, based on all the above information, including the laboratory records and the literature reviews, the following detailed material balance is for the laboratory scale is done.

Overall mass balance on the peeling unit:

Mangos Peeled Mangos

Peeling M 1= 3.2kg M2 = 2.56kg

Peel M3 = 0.64kg

M1 = M2 + M3

3.2 = 2.56 + 0.64

Overall mass balance on the pulping unit:

Peeled Mango Pulping Pulp

M2 = 2.56kg M4 = 1.65kg

Stones, M5 = 0.91kg

M2 = M4 + M5

2.56 = 1.65 + 0.91

Overall mass balance on mixing unit

Honey, M6 = 0.065kg, y6 = 0.17

Pulp Mixing Puree Mix,

M4 = 1.65kg (Blendin g) M9 = 1.75kg

Y4= 0.79 y9 = ?

Lemon Juice, Spices, M8 = 0.005kg, y8 = 0.11

M7 = 0.03kg, y7 = 0.92

Mass balance:

M4 + M6 + M7 + M8 = M9

1.65 + 0.065 + 0.03 + 0.005 = 1.75kg

Water balance:

W4 + W6 + W7 + W8 = W9

=> M4y4 + M6y6 + M7y7 + M8y8 = M9y9

=> (1.65*0.79) + (0.065*0.17) + (0.03*0.92) + (0.005*0.11) = 1.75y9

=> 1.75y9 = 1.3427

=> y9 = 0.767

Therefore, the moisture content of the mixed puree is 76.7%.

Mass balance on the heating unit:

0 o Ti= 20 C Heating T = 75C

Mixed Puree Hot Puree

M10 = 1.75kg M11 = 1.75kg

y10 = 0.767 y11 = 0.767

Here, the input is equal to the output.

M10 = M11, and y10 = y11

Energy balance on the heating unit

The heating rate (heat load) of a heat exchanger (q, kW), required to heat the product (m, kg/s) by a temperature difference (∆T, K or °C), is estimated from the equation:

q = mCp∆T

Where, Cp (kJ/kg K) is the specific heat of the product.

To determine the specific heat capacity of the mixed puree, we use:

Cp, mixed puree = ∑ (CpiMi)

Where, Cpi = The specific heat capacities of each component in the mixture, and

Mi = Mass fractions of each components

The specific heat of the mixed puree is estimated using the Choi and Okos model for determination of specific heat of foods based on Table 4.18 summarized below. 72

Table 4.18 Specific heat relationships for food product components

Therefore, based on the calculations within Table 4.18 the specific heat of the mixed puree was found.

Cp of Mixed Puree at 75oC= 3.45KJ/kg.K . Thus, the heat can be determined by,

Q = MCp∆T

= 1.75kg*3.45KJ/kg.K* (75-20)

= 332.06KJ

Therefore, the heat required to heat the puree is 332.06KJ.

Overall mass balance on the drying unit

Moist Air out, M12

Tray Drying Hot Puree Mango Leather

M11 = 1.75kg

Dry Air in M13 = 0.52kg

Y11 = 0.767 y13 =?

Mass balance:

M11 = M12 + M13

1.75kg = M12 + 0.52kg

M12 = 1.23kg of water

Therefore, 1.23kg of water is removed from the drying process.

Water balance:

M11y11 = M12 + M13y13

1.75*0.767 = 1.23 + 0.52y13

Y13 = 0.2156

Therefore, the final moisture content of the product was 21.6%.

Energy balance for drying:

The parameters that are critical for the production of mango fruit leather were selected and fixed to calculate the air speed of the dryer.

o T4 = 41 C

Moist Air out, G2, y2

Drying Mango Puree Mango Leather

M1 = 1.75kg M2 = 0.52kg

x1 = 0.767 Dry Air in, x2 =0.2156

o T1 =40 C G1, y1 T2 =

o T3 = 50 C

The fixed parameters were as follows:

The relative humidity of the inlet hot air is set at 10% and its temperature at 50ºc.

The following assumptions were made so that the air follows an adiabatic saturation curve (constant wet bulb temperature line) on the Psychrometric chart.

(Cp)air, (Cp)water, (∆Hv)water are independent of temperature at the prevailing process conditions.

The enthalpy changes undergone by the un-evaporated liquid water and the solid components in going from T1 to T2 are negligible as compared to the changes undergone by the entering hot air and the evaporated water.

Even though, the air at the interface could have a relative humidity of closer to 100%, it is the nature of engineers to assume the worst case and benefit. Hence the relative humidity of the out let air is assumed to be 40%.

Then from material balance calculations, Perry’s handbook of chemical engineers and psychrometry the following data is generated:

y1 = 0.00794

y2 = 0.01185

λ = 2382kj/kg

o Cp(product) = 3.452KJ/kg K

Cp(air) = 1.007

Cp(water liquid) = 4.179

Cp(water vapor) = 1.88

Where, λ is the latent heat of vaporization of water at 50ºc. Therefore, the total mass balance and

component balance on the drier solves for the two unknowns, G1 the inlet amount of the hot air and

G2 the outlet amount of wet air in kilo grams.

Total mass balance:

M1 + G1 = M2 + G2

=> M1 - M2 = G2 - G1

=>G2 - G1 = 1.23 ……………. (eq.1)

Component balance on water:

M1x1+G1y1 = M2x2 + G2y2

=> G2y2 - G1y1 = M1x1 - M2x2

=> G2y2 - G1y1 = 1.23 …………... (eq. 2)

We got two equations and two unknowns, G1 and G2.

Then, solve for G1 by first multiplying (eq. 1) by y2:

(G2 - G1 = 1.23) y2; where, y2 = 0.01185

=> G2y2 - G1y2 = 0.0146 ………… (eq. 3)

Then solve (eq. 2) and (eq. 3) simultaneously;

G2y2 - G1y1 = 1.23

(G2y2 - G1y2 = 0.0146) multiply with (-1)

G1 (y2 - y1) = 1.2154 76

G1 = 1.2154

(y2 – y1)

Where y2 = 0.01185

y1 = 0.00794

=> G1 = 310.85kg air and from (eq.1),

G2 - G1 = 1.23

=> G2 = 312.08kg air

Energy balance on the convective drier

Based on the above assumptions the simplified energy balance equation becomes;

Q = (m, evaporated water) (λ) + (m, evaporated water) (cp, water liquid) (T3 – T1) (eq.4)

Q = (1.23*2382.7) + (1.23*4.179)* (10)

=> Q = 2982.13 kj

Therefore, the amount of energy required by the dryer is 2982.13kj.

The quantitative flow diagram for the whole process as per laboratory scale for material balance is presented below in Figure 4.4.

Mangos, 3.2kg Peels, 0.64kg Peeling

Peeled Mangos, 2.56kg

Pulping Stones, 0.91kg

Pulp, 1.65kg

Honey, 0.065kg Mixing Lemon Juice, 0.03kg, M.C=92% (Blending) M.C=17% Spice, 0.005kg, M.C=11%

Mixed Puree, 1.75kg, M.C=76.7% Heating

(800C)

Hot Puree, 1.75kg, M.C=76.7%

Convective Water, 1.23kg Drying

Mango Leather 0.52kg, M.C= 21.6%

Figure 4.4 Quantitative flow diagram for mango leather process

 Product commercialization (Scale up the laboratory scale mango leather process in to small scale processing industry)

The process selected for the manufacture of the mango leathers is semi-continuous even though the drying process is batch. Provisions for possible shutdowns for repairs and maintenance, and seasonal production of mango fruits are incorporated into the design of the process by specifying plant operation for 200 calendar days per year.

The laboratory result shows that one can get an output of 0.52kg of mango fruit leather from 3.2kg of mango fruits. To scale up this in to a small scale processing plant with the overall assumptions of 200kg production of mango leather per day, we need 1230.8kg mango fruits supply per day:

i.e. 3.2kg mango fruit => 0.52kg mango leather

X => 200kg mango leather

Therefore, X = 1230.8kg of mango fruit

The plant operates 200 days per year, so the annual production of mango leather will be: 200kg X 200 = 40,000kg.

Since the intended daily production of mango leather is 200kg, we can take out a scale up factor for multiplying all the laboratory scale results to obtain the daily needs of all the inputs and outputs of the whole process. This can be done by dividing 200kg of leather/day with 0.52kg of leather. Therefore, we get a scale up factor of 384.62 for daily production. Therefore, based on the factor, the quantitative flow diagram for the whole process as per daily basis for material balance is presented below.

On average 5 liters of water is required to wash 1 kilogram of mango fruit. So to wash 1230.8 kg of mangos we need 6154L of water.

Ripened Mangoes

1230.8kg/day

Water in, 6154L/day Waste water out, 6154L/day Washing

Mangos, 1230.8kg/day Peels, 246.2kg/day Peeling

Peeled Mangos, 984.6kg/day

Pulping Stones, 350kg/day

Pulp, 634.6kg/day, M.C=79%

Honey, 25kg/day Lemon Juice, 11.5kg/day, M.C=92% Mixing M.C=17% (Blending) Spice, 1.9kg/day, M.C=11%

Mixed Puree, 673.1kg/day, M.C=76.7% Heating

Hot Puree, 673.1kg/day, M.C=76.7%

Drying Water, 473.62kg/day

Mango Leather 200kg/day, M.C= 21.6%

Figure 4.5 Quantitative flow diagram for daily production of mango leather

Fig. 4.6 Equipment layout for mango leather processing

 Equipment sizing and selection

The equipment design for this preliminary process evaluation involves determining the size of the equipments in terms of the volume, flow per unit time, or surface area. The determination of the equipments capacity per hour basis is done with the general assumption of 200 working days per year and 8 working hours per day with two shifts. Therefore, the production can be further reduced in to an hour basis by taking 200kg of mango leather production per day and assuming the plant operates 8hrs; we can get 25kg/h production of mango leather.

Washing unit equipment selection:

Fruit Washing Machine: Washing is intended to be completed maximum within two hours, so;

Washer Capacity:

1230.8kg = 615 kg/h

Therefore, select a fruit washer with a capacity of washing 700kg of mango fruits per hour.

Peeling unit equipment selection:

Peeler Capacity: peeling is also intended to be completed within maximum of two hours; so,

1230.8kg = 615 kg/h

Therefore, select a fruit peeling machine with a capacity of peeling 700kg of mangos per hour.

Pulping unit equipment selection:

Pulper Capacity: the pulping process is intended to be completed with a maximum of one hour; so,

984.6kg = 984.6kg/h

Therefore, select a pulper with a capacity of pulping 1,000kg of mangos per hour 82

Mixing unit equipment selection:

Mixer (Blending Machine) Capacity: the blending and mixing process together should also be completed within an hour; so,

673kg = 673kg/h

Therefore, select a mixer with a capacity of mixing 700kg of ingredients per hour.

Heating unit equipment selection:

Heat Exchanger Capacity: the heating process can also be finished within an hour, so;

673kg = 673kg/h

Therefore, select a heat exchanger with a capacity of heating 700kg of mixed mango puree per hour.

Drying equipment selection:

Convective hot air dryer:

Drying of mango leather was experimented in laboratory and it was found that, to dry 1.75kg of mango puree with a M.C of 76.7%, 3 trays were used each trays were 25 X 35Cm. Therefore, the total area for drying was 0.265m2. From this result, it can be scaled up to dry 673kg of mango puree with total area of 101.165m2. Therefore, select a convective hot air dryer with a surface area of 105m2 to dry the hot mango puree.

 Economical analysis

Production planning:

Production can be planned using the calculations below and answering the following questions. The information required to do this includes:

200days per year/12months per year = 16 working days on average per month.

How much product (kg) is sold each month?

200kg leather per day * 16days = 3,200kg/month

Answer: 3,200kg/month assuming all the produced mango leathers are sold

How many hours are worked per day?

Answer: 8 hours

How many days are worked per month?

Answer: 16 days on average per month

This information is first used to calculate the daily production rate, so that ingredients and packaging can be ordered. Then the average amount of production per hour (termed the ‘product throughput’) can be calculated to find the size of equipment and numbers of workers required.

Daily production rate:

The daily production rate is calculated as follows:

Production rate (kg/day) = Amount of product sold/month (kg)

Number of day’s production/month

= 3200kg = 200kg/day

16days

This figure is used to decide how much raw material, ingredients and packaging to buy.

Raw materials and ingredients

Having decided how much product to make, a processor needs to calculate how much fruit to buy. This is based first on the recipe for the product and secondly on the likely levels of wastage and losses during the process.

 Calculating weights of ingredients from a recipe for making mango leather

A recipe for mango leather (Table 4.19) shows in the left column of the table below and the amounts of ingredients needed to make 0.52 kg are shown in the right column, with the calculation in the centre.

Table 4.19 Recipes, calculations and amount of ingredients for making Mango leather

Recipe Calculations Amount needed to make 0.52kg of Mango Leather

Mango = 3200g (3200/3300) X 0.52 0.504kg

Honey = 65g (65/3300) X 0.52 0.0102kg

Lemon Juice = 30g (30/3300) X 0.52 0.0047kg

Ground Ginger = 5g (5/3300) X 0.52 0.00079kg

Total = 3,300g 0.52kg

However, the amounts of raw material and ingredients that are calculated from the recipe are not the amounts that are used. Losses arise from peeling, from spoiled raw materials that are thrown away during sorting, from spillage during filling into packs or from food that sticks to equipment and then lost during cleaning. The average typical losses during processing have to be considered during the production of mango leather. These losses can be referred to in Table 4.20 presented below.

Table 4.20 Typical losses during processing of fruits and vegetables

Stages in a Process Typical Losses (%)

Washing Fruits and Vegetables 0-10

Sorting 5-50

Peeling 5-60

Slicing/dicing 5-10

Batch preparation/weighing 2-5

Boiling 5-10

Drying 10-20

Packaging 5-10

Machine Washing 5-20

Accidental Spillage 5-10

Rejected packs 2-5

(does not include evaporation losses)

(Source: Fellows, P., Midway Technology Ltd, Bonsall, UK)

The amount of usable food after raw materials are prepared for processing is known as the ‘yield’ and is calculated as follows:

Yield (%) = Weight of raw material actually used in the process X 100

Weight of raw material that is bought

On average mangos cost 0.6 Birr each and a single fruit weighs 200g (i.e. 3Birr/kg). 3.2kg of mango fruits are bought for 9.6 Birr and after peeling and coring there is 1.65kg available for processing.

Therefore, Yield = 1.65 *100 = 51.56% (i.e. 48.44% is waste)

3.2

The UNIDO Technology Manual (2004) has indicated that the typical losses during the preparation of mango fruits during peeling and de-stoning to be 45%. Therefore, the result of wastage in this case 48.44% is relatively comparable.

The true cost of raw materials depends on the yield and can be calculated as below:

True raw material cost = Supplier cost * 100

% Yield

The true cost of the usable part of a single fruit = 0.6 * 100 = 1.16Birr

51.56

This result also shows the value addition of the product from the raw material after preliminary process.

From the laboratory result theoretically, 0.52kg of mango leather is available for sale. Ignoring other production costs (labor, depreciation etc.) the value of the product is therefore:

Cost of raw materials = Mango + Honey + Lemon juice + Ginger (or Spice)

= 9.6Birr + 2.275Birr + 0.3Birr + 0.5Birr

= 13.15Birr

Cost of raw materials = 13.15Birr = 25.28 Birr/Kg

Weight of product 0.52kg

Therefore, processing has increased the value of the raw materials 13.15/kg to Birr 25.28/kg.

 Cost benefit analysis of Mango leather production

Plant parameters for Mango leather production

Capacity 40,000kg per year

Number of shifts /day 2

Working days/year 200

The amount of total product per year = 40,000kg/yr

The amount of raw materials needed:

- Mango fruits = 246,160kg/yr - Lemon Juice = 2,300kg/yr

- Honey = 5,000kg/yr - Spice (Ground Ginger) = 380kg/yr

 Machinery and equipment

Table 4.21 Machinery and equipment requirements for mango leather production

Item Quantity Capacity Unit price, Birr Total Price, Birr (kg/h)

Fruit washer 1 700 23,520.00 23,520.00

Fruit Peeler 1 700 25,000.00 25,000.00

Fruit pulper 1 500 23,640.00 23,640.00

Mixer (Blender) 1 700 100,000.00 100,000.00

Heat Exchanger 1 700 100,000.00 100,000.00

Tray Dryer 1 200kg/24h 60,000.00 60,000.00

Total 332,160.00

 Manpower requirement

Table 4.22 Manpower required for Mango leather production

Human Resource Number Monthly average Total monthly Total yearly salary, birr salary, birr salary, Birr

Manager 1 3,000.00 3,000.00 36,000

Skilled 4 1,800.00 7,200.00 86,400

Unskilled 10 800.00 8,000.00 96,000

Total 15 5,600.00 18,200.00 218,400.00

 Cost of raw materials

Table 4.23 Raw material costs for Mango leather production

Unit price, Total price, Item Quantity (kg/yr) birr Birr/kg

Mango fruits 246,160 3.00 738,480.00

Honey 5000 35.00 175,000.00

Lemon Juice 2300 10.00 23,000.00

Spices (Ground Ginger) 380 30.00 11,400.00

Total 947,880.00

 Cost of utilities

Table 4.24 Cost of utilities for Mango leather production

Unit price, Total price, Birr Item Quantity birr

Electric Power 70,000kwh 0.90 65,000.00

Water 1,230,800 l 0.005 6,154.00

Total 71,154.00

 Fixed capital cost estimation

Table 4.25 Fixed capital cost estimation for Mango leather production

Item Description / factor Total Cost, Birr

A. a. Equipment 332,160.00

b. Installation 0.47* 332,160.00 156,115.20

c. Instrumentation 0.18* 332,160.00 59,788.80

d. Piping 0.66* 332,160.00 219,225.60

I Direct Costs e. Electrical 0.11* 332,160.00 36,537.60

B. Building +auxiliary 0.70* 332,160.00 232,512.00

C. Service facilities 0.70* 332,160.00 232,512.00

D. Land 0.06* 332,160.00 19,929.60

Total direct cost A+B+C+D 1,288,780.80

A. Engineering & supervision 0.1*1,288,780.80 128,878.08

B. Construction + contractor fee 0.1*1,288,780.80 128,878.08

II. Indirect C. Contingency 0.06*1,288,780.80 77326.848 Costs Total indirect cost A+B+C 335,083.008

III. Fixed capital investment Direct +Indirect cost 1,623,863.808

IV. Working capital 0.15*1,623,863.808 243579.57

V. Total capital investment III +IV 1,867,443.379

 Estimation of Total Product Cost (TPC)

Table 4.26 Estimation of total product cost for Mango leather

Item Description/factor Total cost, Birr

A. a. Fixed Charges

a. Depreciation 0.1*mach. + 0. 02*building 37,866.24 cost

b. Local taxes 0.02*FCI 32477.28 I. Manufacturing cost c. Insurance 0.006* FCI 9743.18

Total of A 80,086.70

B. Direct production cost

Total product cost (tpc) Total fixed charge/0. 15 533911.33

a. Raw material Calculated 947,880.00

b. Utilities Calculated 71,154.00

c. Operating labor (ol) 0.1*tpc 53,391.13

d. Supervisory 0.1*ol 5,339.11

e. Maintenance 0.05*FCI 81,193.19

f. Lab charges 0.12*ol 6406.94

Total of B 1,699,275.69

C. Plant overheads 0.1*tpc 53,391.13

Total manufacturing cost A+B+C 1,832,753.52

II. General a. Administrative cost 0.05*tpc 26,695.57

Expenses b. Distribution 0.1*tpc 53,391.13

c. Research & 0.05*tpc 26,695.57 development

d. Interest 0.05*tpc 26,695.57

Total general expenses 85,477.83

III. Total Product Cost I +II 1,918,231.35

1,918231.35 = 47.96 Birr/kg 40,000.00 Total product cost/kg of mango leather

 Financial evaluation

Assume selling price of 1kg of mango fruit leather = 65.00 Birr

Expecting all produced product will be sold,

Total income = 65*40,000 = 2,600,000.00 Birr

Gross income = total income-total product cost

= 2,600,000.00 – 1,918,231.35 = 681,768.65 Birr

Let the tax rate be 35% (income tax of Ethiopia)

Taxes = 0.35*681,768.65 = 238,619.03 Birr

Net profit = gross income – tax => 681,768.65- 238,619.03= 443,149.62 Birr

netprofit 443,149.62 Return on investment = 100 = 100 = 23.73% totalcapitalinvestment 1,867,443.379

FCI 1,623,863.808 Payback period = = = 3.4 years NP  Depre 443,149.62  37,866.24

CHAPTER 6

CONCLUSIONS AND RECOMMENDATION

6.1 Conclusion

To be competitive and increase the market share and profits, the mango leather processing industry must ensure that its products are of higher quality, less expensive, and more desirable than their competitors, and also safe and nutritious. To meet these standards, the processing industry needs to analyze the mango fruits, before, during and after the manufacturing process. The most important concerns of the mango leather manufacturer is to produce a final product that consistently has the same qualities with overall properties, such as appearance, texture, flavor and also shelf life. However, the properties of the raw ingredients and the processing conditions vary from time to time which causes the properties of the final product to vary, often in an unpredictable way. Therefore, the processing industry has to wisely control the manufacturing process to produce a final product with consistent properties. This can be achieved by characterizing and measuring the properties of the incoming raw materials, to ensure that they meet certain minimum standards of quality that have previously been defined by the manufacturer. If the industries standards are not met it has to reject the material since variations in its properties might lead to changes in the properties of the final product.

The nutritional content of the puree, after being mixed with honey and lemon juice, increased for both varieties while the moisture content decreased. The viscosity of Tommy Atkins variety mango puree mix was found to be lower than that of Keitt variety. The drying time was generally shorter at higher temperatures due to quick removal of moisture. The puree load also affected the drying time at all drying temperatures. Generally, the drying time was considerably prolonged for more than 7 h for 0.6g/cm2 puree load at all drying air temperatures (600C, 700C and 800C). The result of the analysis showed 70.3% moisture loss after drying process is completed. The texture analysis result of the final mango leather showed that 4 sheets and 5 sheets of leather with 5mm and 6mm thickness respectively were found to be suitable for a single bite. The results of the proximate analysis for both varieties of mango fruit leather indicated that the processing affected the nutritional composition of the fruit leather. The vitamin C content was also found to be dependent on all drying temperature, puree load and fruit variety. The vitamin C content of the Keitt mango

leather (26.93%) is greater than that of Tommy Atkins mango leather (22.71%). When compared to the fresh puree mix, the Keitt mango leather is decreased by 39.66% and that of the Tommy Atkins mango leather is decreased by 57.82%. The microbiological analysis of the mango fruit leather has also indicated that the products are generally safe for consumption. The sensory analysis result also indicated that the Tommy Atkins mango leathers dried at 60 and 700C with 0.4 and 0.6 g/cm2 puree loads were well accepted by the panelists especially in terms of color, taste, flavor and overall acceptability.

Currently in Ethiopia there is no fruit processing industry involved in fruit leather development process. Most fruit processing industries are interested in production of juices and similar types of products. However, fruit leather production can easily be implemented taking advantage of utilizing fruit normally not selected for juice making, freezing or other processes. Mangos can be preserved by production of mango fruit leathers without any addition of preservatives. This meets consumer demand for health food products, in a form of fruit leathers. In the country, the production of fruit leathers is almost unknown and if this project were to be implemented, it will be very attractive and profitable. Besides, the application of this kind of simple processing technology based on drying principles is one way of minimizing postharvest loss.

The project has designed and developed the process for the production of mango fruit leather at a small scale level within Ethiopia. It has been demonstrated that the mango fruit leather production would result in a feasible and strong return on investment. Therefore, investors who are interested in food processing can take advantage of seasoning and diversifying mango products within the country and develop a value added product with strong profit.

6.2 Recommendation

The mango properties during processing have to be monitored and measured. So that if there is any problem developed it can be quickly detected, and the process will be adjusted to compensate for it. This helps to improve the overall quality of the mango leather and reduce the amount of material and time wasted. The final mango fruit leather product has to be also analyzed and characterized to ensure that it retains its desirable properties up to the time when it is consumed, meets the appropriate high quality requirements, and that it is safe for consumption.

By mixing different proportions of various types of fruits, fruit leathers can be developed to nutritionally enrich the final product and attract customers’ attention. The fruit leather products are being targeted at consumers’ requirement with increased awareness towards health food choices. Consequently fruit leathers are being marketed as luxury health food products in Europe. Therefore, if mango fruit leathers can be produced and exported, it will contribute to the country’s foreign exchange. Once the technology is applied and implemented for mango fruit processing industry, it can also be used for processing of different types of fruit leathers at different seasons of the year whenever the fruit types are abundant. So it is recommended that further researches need to be conducted on the processing of fruit leathers, fruit bars and dried fruits and the process needs to be designed and implemented within the country in the near future.

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ANNEXES

Annex 1 Determination of aerobic colony count for mould and yeast in food (NMKL, No. 98, 1997)

Method principle

The aerobic colony count estimates the number of viable aerobic mould and yeast per g or ml of product. A portion of the food homogenate is mixed with a specified agar medium and incubated under specific conditions of time and temperature. It is assumed that each viable aerobic mould/ yeast will multiply under these conditions and give rise to a colony.

Responsibilities: All trained stuff with adequate experience

Positive Control: Any spp. of mold and yeast.

Negative Control: check sterility of PDA medium and diluents used by pouring control plates and incubate at 37oc and 22 oC for 5-7 days.

Equipment to Calibrate: Incubator 37°C and 22oC, Autoclave, and pH-meter. Media: PDA

Diluents: peptone water

Procedure:

1. Preparation of food homogenate

2. Dilution

2.1 Mix homogenate by shaking and pipette 1ml into a tube (labled102 containing 9ml of normal saline. Mix carefully by aspirating 10 times with a pipette

2.2 From the first dilution, transfer with the same pipette 1ml to 2nd dilution tube containing 9ml of the Ns, Mix with a fresh pipette

2.3 Repeat using 3rd or more until the required numbers of dilutions is made

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2.4 shake all dilution carefully.

3. Pour plating

3.1 Pipette 1ml of the food homogenate and of each dilution of the homogenate into each of the appropriately marked duplicate dishes.

3.2 Pour into each petridish 15-20ml of the PDA.

3.3 Mix the sample dilution and agar medium thoroughly and uniformly, allow solidifying.

4. Incubation. Incubate the prepared dishes, inverted, at 370c and 220c for 5-7 days.

5. Counting the colonies. Following incubation, count all colonies on dishes containing 30- 300 colonies and recorded the results per dilution counted.

Verification: If there is growth on the negative control or if there is no growth on the positive controls the test should be repeated.

Expressions of results: calculate the average count and multiply by the dilution. And express the result in cfu per g –ml (if a liquid sample)

- the result at 370c reported as yeast and mold count at 370c

- the result at 220c reported as yeast and mold count at 220c

Annex 2 Determination of Aerobic Plate Counts (APC) in food (NMKL, No. 86, 2006)

Method principle

The aerobic colony count estimates the number of viable aerobic bacteria per gm or ml of a product. A portion of the diluted sample mixed with a specified agar medium and incubated under specific temperature for 48 hr. It is assumed that each viable aerobic bacterium will multiply under these conditions and give raise to colonies.

Terms:

Mesophillic bacteria: an organism whose optimum growth lies within a range generally accepted as 20-450C

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Psychrophilic bacteria: an organism which grows optimally at or below 15 0C, which has an upper limit for growth at 20 0C , and which has a lower limit of 0 0C or lower.

Termophilic bacterial: an organism whose optimum growth temperature is >45 0C

Responsibilities: All trained stuff with adequate experience.

Positive Control: Reference material with known aerobic plate count.

Negative Control: check sterility of PCA medium and diluents used by pouring control plates.

0 0 Equipment to Calibrate: Incubator37 C for Mesophillic bacteria, Incubator 55 C for Termophilic 0 bacterial, Refrigerator 2-8 C for Psychrophilic bacteria, Autoclave, PH meter, Safety cabinet, Pipettes controllers, Colony counting device, Centrifuge optional, only for some food type, Stomacher optional, only for none liquid sample, and Digital balance.

Media: PCA

REAGENT: 2%sodium citrate (tempered to 45 0c) (for cheese sample only)

Diluents: peptone water diluents (SOP 4.2.15)

Procedure:

1. Sample preparation

Transfer 10ml of liquid sample to 90ml of diluents or 25g of sample to 225 ml of diluents in a flask if shaker used or in sterile plastic bag if stomacher used to make 101 dilutions (the first dilution) Mix well with shaker/stomacher

2. Dilutions

Mix the first dilution by shaking then pipette 1ml into a tube (labled102) containing 9 ml of normal saline. Mix carefully by aspirating 10 times with a pipette.

From the 102 dilution, transfer with the same pipette 1ml to the tube (labled103) containing 9ml of the diluent, Mix with a fresh pipette. Repeat until the required numbers of dilutions are made.

3. Pour plating

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Pipette 1ml of each serial dilution into each of the appropriately marked duplicate dishes. Pour 15- 20ml of the molten PCA kept at 45 0C into each Petri dish. Mix it thoroughly and allow it to solidify.

4. Incubation.

Incubate the dishes, inverted, at 35 0C or for dairy products at 320C for 48 hr.

N.B: Avoid excessive humidity in the incubator, to reduce the tendency for spreader formation, but prevent excessive drying of the medium by controlling ventilation and air circulation. Agar in plates should not lose weight by more than 15% during 48 hours of incubation.

5. Counting the colonies.

Following incubation, count all colonies within the range of 30-300 colonies and record the results per dilution counted.

Sample preparation: weigh 10g of the sample in to a sterile 250ml Erlenmeyer flask; marked to indicate 100ml volume. Add sterile saline peptone to 100ml mark. Dissolve and shake thoroughly.

Dilution: 1:10, 1:100, 1:1000, etc

Dilution factor: 1 x 101, 1×102, 1× 103 etc

Inoculation: Pipette 1ml of the food homogenate and of each dilution of the homogenate into each of the appropriately marked duplicate dishes followed by pour plating of PCA.

Incubation: Incubate the prepared dishes, inverted, at 350C for 48 hours, and for dairy products at 320 C for 48±3 hrs.

Counting colonies: Following incubation, count all colonies on dishes containing 30-300 Colonies, including those of pinpoint size and recorded the results per dilution counted.

Verification: If there is growth on the negative control and /or no growth on the positive control the test should be repeated with the corrected media

Expression of results: express the result in cfu per g /ml (if a liquid sample)

Calculation formula: Use the best two consecutive dilutions, as n1 and n2 to calculate the results.

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N =C/V (n1 + 0.1n2) d

Where, C = is the sum of colonies on all plates counted

V = is the volume applied to each plate

n1= is the number of plates counted at first dilution.

n2= is the number of plates counted at second dilution,

d = is the dilution from which first count was obtained.

N= is the average plate count.

Round the result to two significant figures and express it as a number between 1.0and 9.9 multiplied by 10 x where X is the appropriate power of 10.

Annex 3 Enumeration of coliform (MPN) (NMKL, No. 44, 2004)

Method principle

Graduated amount of food (diluted) sample are transferred to a series of fermentation tubes containing lactose or lauryl sulphite tryptose broth of proper strength, it is usual practice to inoculate to three fermentative tubes. The tubes are incubated at 35+ 0.5 0C for 24 and 48hrs.The formation of gas in any of the tubes with in 48hr ,regardless of the amount, constitutes as positive for coliform and the absence of gas formation with in this period considered as negative for coli form . Confirm the coliform by BGBB

Responsibilities: All trained stuff with adequate experience

0 Positive Control: any Coliform spp. For total coliform test 44.5 C gas positive E.coli for fecal coliform test.

Negative Control: Uninoculated tubes with the media and inverted tube 0 44.5 C negative E.aerogenes for fecal coliform test.

0 Equipment to Calibrate: Incubator37 C, PH meter, Safety cabinet, Pipettes controllers, Colony counting device, Centrifuge optional, only for some food type, 0 Stomacher optional, only for none liquid sample, Digital balance, and Water bath 44 C.

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Media: LSTB, BGBB, EC broth,

Diluents: Peptone water

Procedure:

Presumptive test for coliform group (MPN)

1. Preparation of the first dilution (101)

Transfer 10ml of liquid sample to 90ml of diluents or 25g of sample to 225 ml of diluents in a flask if shaker used or in sterile plastic bag if stomacher used to make 101 dilution (the first dilution) and Mix well with shaker/stomacher. Mix homogenate by shaking and pipette 1ml into a tube containing 9 ml of normal slain. Mix carefully by aspirating 10 times with a pipette. From the first dilution, transfer with the same pipette 1ml to 2nd dilution tube containing 9ml of the Ns, Mix with a fresh pipette. Repeat using 3rd or more until the required numbers of dilutions are made. Shake all dilution carefully.

2. Inoculation

Inoculate each of 3 replicate tubes of LSTB broth per dilution (containing inverted tubes) with 1ml of the previously prepared 1:10, 1:100 and 1:1000 dilutions using sterile pipette for each dilution.

3. Incubation: Incubate the LSTB tubes at 35+ 0.5 0C for 48hrs.

4. Reading: Record tubes showing gas production after 48hr

5. Result reading: Record all tubes showing gas within 48+ 2hrs and refer to MPN table for the 3 tube dilution and report results as the presumptive MPN of coliform bacteria per g (or ml of liquid product).

6. Confirmed test for coliform group (MPN)

Subculture all positive tubes showing gas within 48 + 2 hours 2 hours in to BGB broth by means of the 3 mm loop. Incubate all BGB tubes at 35+ 0.5 0C for 48 + 2 hours. Record all BGB tubes showing gas, and refer to the MPN table for 3 tube dilution. Report results as confirmed MPN of coliform bacteria per g (or ml of liquid product).

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Annex 4 Determination of coliforms, fecal coliforms and E. coli by using MPN technique (FDA/BAM, 2006)

50 g of the sample was weighted into sterile high-speed blender jar. Frozen samples can be softened by storing it for <18 h at 2-5°C, but do not thaw. 450 ml of Butterfield's phosphate- buffered and water were blended for 2 min. If <50 g of sample are available, weigh portion that is equivalent to half of the sample and add sufficient volume of sterile diluents to make a 1:10 dilution. The total volume in the blender jar should completely cover the blades.

Decimal dilutions with sterile Butterfield's phosphate diluents were prepared. Number of dilutions to be prepared depends on anticipated coliform density. Shake all suspensions 25 times in 30 cm arc or vortex mix for 7 s. Do not use pipettes to deliver <10% of their total volume. Transfer 1 ml portions to 3 tubes for each dilution for at least 3 consecutive dilutions. Hold pipette at angle so that its lower edge rests against the tube. Let pipette drain 2-3 s. Not more than 15 min should elapse from time the sample is blended until all dilutions are inoculated in appropriate media. Incubate tubes at 35°C. Examine tubes and record reactions at 24 ± 2 h for gas, i.e., displacement of medium in fermentation vial or effervescence when tubes are gently agitated. Re-incubate gas- negative tubes for an additional 24 h and examine and record reactions again at 48 ± 2 h. Perform confirmed test on all presumptive positive (gas) tubes.

Annex 5 Enumeration of Staphylococcus aureus (NMKL, No. 66, 2003)

Method principle

Certain staphylococci produce enterotoxins which cause food poisoning. This ability to produce enterotoxins, with few exceptions, is limited to those strains that are coagulase positive, and /or produce a heat stable nuclease (TNase). This method determines the presence of S. aureus by plating known quantities of (dilutions of) food sample onto a selective agar. After incubation presumptive staphylococcal colonies are selected and subjected to confirmatory tests from the results of these tests the number of S. aureus per g or ml of the food is calculated .The quantity that present may indicate a potential for the presence of enterotoxin , or they may also indicate a lack of adherence to good hygienic practices.

Responsibilities: All trained stuff with adequate experience

Positive Control: S.aures

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Negative Control: E.coli

Equipment to Calibrate: Incubator 37°C, Autoclave, pH-meter Media: Baird-parker agar and Mannitol salt agar

Reagent: Human plasma or commercial rabbit plasma

Diluents: Normal saline (Ns)/peptone water

Sample preparation:

Weigh 10g of the sample in to a sterile 250ml Erlenmeyer flask marked to indicate 100ml volume. Add sterile normal saline to 100ml mark. Dissolve and shake thoroughly.

Procedure (1): Using Baird-parker agar media

1. Preparation of food homogenate

Transfer 10g of sample with sterile spoon or other depending on the sample type in to a sterile250ml Erlenmeyer flask containing 90ml of normal saline.

2. Dilution

2.1 mix homogenate by shaking and pipette 1ml into a tube containing 9ml of normal slain. Mix carefully by aspirating 10 times with a pipette

2.2 From the first dilution, transfer with the same pipette 1ml to 2nd dilution tube containing 9ml of the Ns, Mix with a fresh pipette

2.3 repeat using 3rd or more until the required numbers of dilutions are made

2.4 shake all dilution carefully.

3. Pipette 0.25 ml of the material on the plates (two plates for each dilution) and spread with a sterile bent glass rod. The plates are incubated at 370c for 24- 48 hr.

4. select plates with 30-300 separate colonies which are black and shiny with narrow white margins and surrounded by the zones extending in the opaque medium .Mark the position of these colonies and re-incubate for 24-hrs. Count all colonies with the above appearance that developed in the second 24 hrs incubation and submit these for coagulase test. Then total the

109 colonies which produced clear zones in both periods of incubations. Multiply by 4 and by the dilution factor to calculate the number of staphylococcus auras per ml of sample.

Procedure (2): Using Mannitol salt agar media

Inoculate 0.1ml of the sample into the surface of the medium. Incubate as above and count the typical colonies which form yellow zones and not those surrounded by red or purple zones .This give the number of suspected staphylococcus.

Dilution: 1:10, 1:100, 1:100, etc

Dilution factor : 1 x 101, 1×102, 1×103

Inoculation: spread with a sterile bent glass rod

Incubation: Incubate the prepared dishes, inverted, at 370c for 48 h

Counting colonies: following incubation, count all colonies on dishes containing 30-300 colonies and recorded the results per dilution counted.

Verification: If there is growth on the negative control or no growth on the positive control the test should be repeated.

Expression of results: after calculating the average count and multiply by the dilution express the result in cfu per g or ml (if a liquid sample).

Annex 6 Isolation of Salmonella (NMKL, No. 71, 2005)

Method principle

The procedure consists of six distinct stages. The initial handling of the food and the Non-selective enrichment stage (pre-enrichment) very according to the type of food examined.

Non- Selective Enrichment (Pre enrichment)

The test sample is initially inoculated into a non- inhibitory liquid medium to favors the repair and growth of stressed or sub lethally- injured salmonellae arising from exposure to heat, freezing, desiccation, preservatives, high osmotic pressure or wide temperature fluctuations.

Selective Enrichment

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Replicate portions of each pre-enrichment culture are inoculated into two enrichment media to favor the proliferation of salmonellae through a selective repression or inhibition of the growth of competing microorganism.

Selective Plating

Enrichment cultures are streaked onto selective differential agars for the isolation of salmonellae.

Purification

Presumptive Salmonella isolates are purified on MacConkey agar plates or SS agar plates.

Biochemical Screening

Isolates are screened using determinant biochemical reactions.

Serological Identification

Polyvalent and / or somatic grouping antisera are used to support the tentative identification of isolates as members of Salmonella spp. If available, complete sero-typing is essential.

Responsibilities: All trained stuff with adequate experience

Positive control: Salmonella spp.

Negative control: Uninoculated media

Equipment to calibrate: Incubator 37oC, Blender, stomacher or other homogenizing device.

Medium: Nutrient Broth (NB), Trypticase ( Tryptic, Tryptone) Soy Broth, Brilliant Green Water.

Buffered peptone Water (BPW), Skim Milk Medium, Tetrathionate Brilliant Green Broth (TBG), Selenite Cystine Broth (SC), Bismuth Sulfite Agar (BS), Brillian, Green Sulfa Agar (BGS), MacConkey Agar, SS agar, Nutrient Agar, Triple Sugar Iron Agar (TSL), Lysine Iron Agar (LIA) and Urea Agar ( Christensen's).

Reagent

1 Commercial biochemical test kits.

2 Polyvalent and single grouping somatic (O) and flagellar (H) antisera.

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3. Physiological Saline.

Procedure

Handling of Sample Units

Analyze samples as soon as possible. If necessary, store samples under time and temperature conditions that will prevent the growth or death of native micro flora. If sample units have been abused in transit, re-sampling of the lot should be carried out.

Frozen Foods; sample units that show no signs of thawing upon receipt may be stored in the freezer at- 100C to - 20 0C. Dried and shelf stable foods may be stored at room temperature. Refrigerate all other foods, including those that are received in a partially thawed condition; analyze these samples as soon as possible preferably within 24 h of receipt. Thaw frozen samples at room temperature within 60 min, if this is not possible, thaw the samples at refrigerator (4 to 100C) temperature.

NOTE:

a) Large samples (e.g. whole chicken ) may not readily thaw at refrigerator temperatures. For greater expediency, enclose the frozen sample in a heavy- walled paper bag and thaw overnight at room temperature. This technique maintains the product surface cold during the thawing process.

b) Appropriate containers should ensure that the drippings from the product do not contaminate the laboratory environment.

If the sample unit received for analysis is less than the recommended analytical unit, analyze the entire amount and record the weight used

Blending of samples should be limited to the minimum time required to produce a homogeneous suspension. Excessive blending could result in physical damage that would adversely affect the viability of endogenous micro flora. For products that do not require blending; disperse the analytical unit into the appropriate pre-enrichment broth.

Use aseptic techniques and sterile equipment at all stages of analysis. Containment during the handling of powdered products is critical if cross- contamination of the work environment is to be avoided.

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Non-selective Enrichment (Pre-enrichment)

Compositing of Analytical Units

To reduce the workload, up to 15x25g (ml) analytical units may be composited into a single test sample (e.g. 375 g or ml). If a sample unit consists of more than one container, aseptically mix the contents of the containers prior to withdrawal of the analytical unit. If not possible or practical, the analytical unit shall then consist of equal portions from each of the containers

Sample Analysis

The required analytical unit is dispersed into a suitable active enrichment broth Nutrient broth (NB) and buffered peptone water (BPW) are equally reliable and can be used interchangeably as general purpose pre-enrichment. If the pH of the pre-enrichment mixture lies outside the range of 6.0-7.0, adjust with 1N Na OH or 1N HCl.

NOTE; if the sample unit consists of a container with little food material, thoroughly rinse the interior of the container with a suitable pre-enrichment broth medium and incubate the rinse in a sterile flask. This eventuality is more frequently encountered in situations involving consumer complaints or food poisoning investigations. Positive Salmonella and a negative medium control should be set up in parallel with the test samples. Incubate the pre-enrichment mixture and the positive and negative controls at 35±0.5 0C for 18 - 24 h.

Selective Enrichment

With a sterile pipette, 1.0 ml of the pre-enrichment culture into each of 9 ml of selenite cystine (SC) and tetrathionate brilliant green (TGB) broths. Incubate SC and TGB broths for 24±2 h at 35±0.50C and 43±0.50C, respectively.

Selective plating

Streak replicate loopful of each selective enrichment culture onto BS and BGS agar to obtain well isolated colonies. The enrichment cultures may be streaked onto additional plating media for the isolation of salmonella. Incubate plates at 35± 0.50C for 24±2 h.

If colonies suggestive of Salmonella have not developed on BS plates, incubate for an additional 24±2. Examine incubated plates for colonies suggestive of Salmonella. Typical Salmonella usually occur as pink to fuchsia colonies surrounded by red medium on BGS agar and 113

as black colonies on BS agar with or without a metallic sheen, and showing a gradual H2S- dependent blackening of the surrounding medium with increasing incubation time.

NOTE:

Lactose- and/or sucrose- fermenting Salmonella strains develop a coliform- like (greenish) appearance on BGS agar. A heavy growth of non- salmonellae may also mask the presence of Salmonella on this medium. b. BS agar can retard the growth of Salmonella serovars other than S. typhi unless poured plates are refrigerated (4 to 100C) for 24 h prior to streaking. The absence of suspect colonies on the plates indicates that the analytical or composite test samples did not contain Salmonella spp.

Purification

Streak suspect colonies onto MacConkey agar for purification, Incubate plates at 35±0.50C for 24±2 h .Typical Salmonella colonies are lactose- negative and will appear as colorless colonies on this medium. However, lactose- positive biotypes will occur as pink colonies.

Biochemical Screening

With a sterile needle, inoculate suspect colonies into the biochemical media or in commercial diagnostic kits that would yield equivalent results. Incubate the biochemical media for 18 - 24 h at 35 ± 0.50C.

NOTE: Erroneous biochemical results may be obtained if tubes are not loosely capped during incubation.

Commercial diagnostic kits may be used to obtain detailed biochemical profiles of bacterial isolates. If none of the isolates from a particular analytical unit are suggestive of Salmonella, the analytical unit is considered to be free of salmonellae. If the presence of Salmonella is suspected, proceed with serological testing. If serological testing is not to be performed within 72 h, inoculate suspect isolates into nutrient agar slants and incubate at 35 ± 0.50C for 24 ± 2 h. Store the agar slants at refrigerator (4 to 100C) temperature. Nutrient agar slants that have been stored for more than 72 h should not be used for serological testing. Prepare fresh agar slants for this purpose.

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Annex 7 Proximate compositions of the Fruit Leathers

7.1 Tests of Between-Subjects Effects on Moisture Content of the Fruit Leather

Dependent Variable: Moisture content

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 69.598a 11 6.327 11165.420 .000

Intercept 6071.893 1 6071.893 1.072E7 .000 temp 32.107 2 16.054 28329.735 .000

Pload 11.234 1 11.234 19824.735 .000 variety 3.241 1 3.241 5720.029 .000 temp * Pload 8.646 2 4.323 7629.029 .000 temp * variety 9.514 2 4.757 8394.971 .000

Pload * variety .558 1 .558 984.971 .000 temp * Pload * variety 4.297 2 2.148 3791.206 .000

Error .007 12 .001

Total 6141.497 24

Corrected Total 69.605 23 a. R Squared = 1.000 (Adjusted R Squared = 1.000)

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7.2 Tests of Between-Subjects Effects on Protein Content of the Fruit Leather

Dependent Variable: Protein

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 1.900a 11 .173 40.506 .000

Intercept 134.213 1 134.213 31467.881 .000 temp .913 2 .456 106.973 .000

Pload .107 1 .107 25.087 .000 variety .052 1 .052 12.274 .004 temp * Pload .094 2 .047 10.973 .002 temp * variety .442 2 .221 51.782 .000

Pload * variety .007 1 .007 1.533 .239 temp * Pload * variety .287 2 .143 33.607 .000

Error .051 12 .004

Total 136.165 24

Corrected Total 1.952 23 a. R Squared = .974 (Adjusted R Squared = .950)

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7.3 Tests of Between-Subjects Effects on the Fat Content of the Fruit Leather

Dependent Variable: Fat

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 25.963a 11 2.360 22.445 .000

Intercept 154.642 1 154.642 1470.536 .000 temp .304 2 .152 1.445 .274

Pload 9.604 1 9.604 91.323 .000 variety 1.383 1 1.383 13.153 .003 temp * Pload .192 2 .096 .911 .428 temp * variety 1.329 2 .664 6.317 .013

Pload * variety 11.931 1 11.931 113.453 .000 temp * Pload * variety 1.222 2 .611 5.810 .017

Error 1.262 12 .105

Total 181.867 24

Corrected Total 27.225 23 a. R Squared = .954 (Adjusted R Squared = .911)

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7.4 Tests of Between-Subjects Effects on the Crude Fiber of the Fruit Leather

Dependent Variable: Crude Fiber

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 15.868a 11 1.443 324.463 .000

Intercept 1065.973 1 1065.973 239764.603 .000 temp 5.175 2 2.587 581.979 .000

Pload .572 1 .572 128.718 .000 variety .036 1 .036 8.176 .014 temp * Pload .425 2 .213 47.824 .000 temp * variety 1.825 2 .912 205.236 .000

Pload * variety .026 1 .026 5.819 .033 temp * Pload * variety 7.808 2 3.904 878.150 .000

Error .053 12 .004

Total 1081.895 24

Corrected Total 15.921 23 a. R Squared = .997 (Adjusted R Squared = .994)

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7.5 Tests of Between-Subjects Effects on the Ash Content of the Fruit Leather

Dependent Variable: Ash Content

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 1.758a 11 .160 4.006 .012

Intercept 92.932 1 92.932 2329.111 .000 temp .713 2 .356 8.934 .004

Pload .170 1 .170 4.266 .061 variety .258 1 .258 6.458 .026 temp * Pload .335 2 .167 4.193 .042 temp * variety .019 2 .009 .235 .794

Pload * variety .067 1 .067 1.672 .220 temp * Pload * variety .198 2 .099 2.475 .126

Error .479 12 .040

Total 95.169 24

Corrected Total 2.237 23 a. R Squared = .786 (Adjusted R Squared = .590)

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7.6 Tests of Between-Subjects Effects on the Carbohydrate Content of the Fruit Leather

Dependent Variable: Carbohydrate

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 71.128a 11 6.466 42.520 .000

Intercept 119469.370 1 119469.370 785595.071 .000 temp 34.480 2 17.240 113.366 .000

Pload .073 1 .073 .477 .503 variety .031 1 .031 .203 .661 temp * Pload 2.745 2 1.373 9.025 .004 temp * variety 9.147 2 4.574 30.074 .000

Pload * variety 20.387 1 20.387 134.061 .000 temp * Pload * variety 4.265 2 2.133 14.024 .001

Error 1.825 12 .152

Total 119542.324 24

Corrected Total 72.953 23 a. R Squared = .975 (Adjusted R Squared = .952)

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Annex 8 Vitamin C content of the Fruit Leather

8.1 Tests of Between-Subjects Effects on the Vitamin C content of the Fruit Leather

Dependent Variable: Vitamin C

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 1777.290a 11 161.572 543.837 .000

Intercept 14791.232 1 14791.232 49786.062 .000 temp 418.564 2 209.282 704.425 .000

Pload 374.065 1 374.065 1259.072 .000 variety 106.977 1 106.977 360.076 .000 temp * Pload 2.734 2 1.367 4.601 .033 temp * variety 663.752 2 331.876 1117.067 .000

Pload * variety .988 1 .988 3.326 .093 temp * Pload * variety 210.210 2 105.105 353.775 .000

Error 3.565 12 .297

Total 16572.086 24

Corrected Total 1780.855 23 a. R Squared = .998 (Adjusted R Squared = .996)

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Annex 9 Sensory Characteristics of the Fruit Leather

9.1 Tests of Between-Subjects Effects on the Color of Fruit Leather

Dependent Variable: Color

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 29.383a 11 2.671 8.687 .000

Intercept 1204.167 1 1204.167 3915.989 .000 temp 1.441 2 .720 2.343 .138

Pload .240 1 .240 .780 .394 variety 24.000 1 24.000 78.049 .000 temp * Pload .243 2 .121 .394 .683 temp * variety 1.852 2 .926 3.012 .087

Pload * variety .060 1 .060 .195 .667 temp * Pload * variety 1.547 2 .774 2.516 .122

Error 3.690 12 .308

Total 1237.240 24

Corrected Total 33.073 23 a. R Squared = .888 (Adjusted R Squared = .786)

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9.2 Tests of Between-Subjects Effects on the Aroma of the Fruit Leather

Dependent Variable: Aroma

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 4.331a 11 .394 3.436 .022

Intercept 1113.844 1 1113.844 9720.818 .000 temp .390 2 .195 1.702 .224

Pload .034 1 .034 .295 .597 variety 2.734 1 2.734 23.858 .000 temp * Pload .210 2 .105 .916 .426 temp * variety .190 2 .095 .829 .460

Pload * variety .070 1 .070 .615 .448 temp * Pload * variety .703 2 .352 3.069 .084

Error 1.375 12 .115

Total 1119.550 24

Corrected Total 5.706 23 a. R Squared = .759 (Adjusted R Squared = .538)

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9.3 Tests of Between-Subjects Effects on the Taste of the Fruit Leather

Dependent Variable: Taste

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 8.935a 11 .812 2.291 .085

Intercept 1166.220 1 1166.220 3288.988 .000 temp .323 2 .162 .456 .644

Pload .570 1 .570 1.609 .229 variety 3.300 1 3.300 9.308 .010 temp * Pload 1.903 2 .952 2.684 .109 temp * variety 1.703 2 .852 2.402 .133

Pload * variety .120 1 .120 .340 .571 temp * Pload * variety 1.013 2 .507 1.429 .278

Error 4.255 12 .355

Total 1179.410 24

Corrected Total 13.190 23 a. R Squared = .677 (Adjusted R Squared = .382)

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9.4 Tests of Between-Subjects Effects on the Flavor of the Fruit Leather

Dependent Variable: Flavor

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 7.943a 11 .722 2.541 .062

Intercept 1131.627 1 1131.627 3982.264 .000 temp .271 2 .135 .477 .632

Pload .375 1 .375 1.320 .273 variety 3.527 1 3.527 12.411 .004 temp * Pload .772 2 .386 1.359 .294 temp * variety 1.031 2 .515 1.814 .205

Pload * variety .042 1 .042 .147 .708 temp * Pload * variety 1.926 2 .963 3.389 .068

Error 3.410 12 .284

Total 1142.980 24

Corrected Total 11.353 23 a. R Squared = .700 (Adjusted R Squared = .424)

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9.5 Tests of Between-Subjects Effects on the Toughness of the Fruit Leather

Dependent Variable: Toughness

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 20.741a 11 1.886 5.220 .004

Intercept 853.234 1 853.234 2361.893 .000 temp 3.123 2 1.561 4.322 .039

Pload 4.594 1 4.594 12.716 .004 variety 4.950 1 4.950 13.704 .003 temp * Pload .857 2 .429 1.187 .339 temp * variety 3.816 2 1.908 5.281 .023

Pload * variety 1.354 1 1.354 3.747 .077 temp * Pload * variety 2.047 2 1.024 2.834 .098

Error 4.335 12 .361

Total 878.310 24

Corrected Total 25.076 23 a. R Squared = .827 (Adjusted R Squared = .669)

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9.6 Tests of Between-Subjects Effects on the Overall Acceptability of the Fruit Leather

Dependent Variable: Overall Acceptability

Type III Sum of Source Squares df Mean Square F Sig.

Corrected Model 16.005a 11 1.455 8.455 .000

Intercept 1119.300 1 1119.300 6504.409 .000 temp 1.961 2 .980 5.697 .018

Pload 1.550 1 1.550 9.010 .011 variety 8.050 1 8.050 46.782 .000 temp * Pload .881 2 .440 2.559 .119 temp * variety 2.456 2 1.228 7.136 .009

Pload * variety .220 1 .220 1.281 .280 temp * Pload * variety .886 2 .443 2.574 .117

Error 2.065 12 .172

Total 1137.370 24

Corrected Total 18.070 23 a. R Squared = .886 (Adjusted R Squared = .781)

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Pic. 6 Keitt Mango grown in Assossa region Pic. 7 Tommy Atkins Mango grown at Awara Melka in Afar region

Pic. 8 Oven drying of Mango leather Pic. 9 Tommy Atkins Mango leather in the middle of two Keitt variety leathers

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A. Tommy Atkins Mango puree B. Keitt Mango Puree

Pic. 10 The difference between the Tommy Atkins and Keitt variety Mango puree

Pic. 11 Oven dried Keitt variety Mango fruit leather

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Pic. 12 Tommy Atkins Mango fruit leather

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Pic. 13 Keitt variety Mango fruit leather

Pic. 14 Tommy Atkins variety Mango fruit leather

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Pic. 15 Keitt Mango leather

Pic. 16 Tommy Atkins Mango leather

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Pic. 17 Mango Fruit Leathers produced from Tommy Atkins and Keitt varieties of mango fruits

Pic. 18 Storage of Mango fruit leathers in a refrigerator

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Declaration

I, the undersigned, declare that this thesis is my original work and has not been presented for a Degree in any other University, and that all sources of materials used for the thesis have been duly acknowledged.

Name: Binyam Teshome Tesfaye

Signature: ______

Place: Addis Ababa, Ethiopia

Date of submission: ______

This thesis has been submitted for examination with my approval as University advisor.

Name: Mr. Adamu Zegeye

Signature: ______

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