BELINDA AGYEI- POKU FINAL THESIS.Pdf

KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, KUMASI

COLLEGE OF SCIENCE

DEPARTMENT OF FOOD SCIENCE AND TECHNOLOGY

THE EFFECT OF PRE- TREATMENT AND OVEN DRYING TEMPERATURES ON THE

NUTRITIONAL, ANTI-NUTRITIONAL VALUES AND COLOUR PROPERTIES OF THE

FRUITS OF SOLANUM TORVUM

THIS DESSERTATION IS PRESENTED TO THE DEPARTMENT OF FOOD SCIENCE

AND TECHNOLOGY IN PARTIAL FULFILMENT OF THE REQUIREMENT OF

MASTER OF SCIENCE (MSc) DEGREE (HONS) IN FOOD QUALITY MANAGEMENT

BELINDA AGYEI- POKU

JULY, 2017

DECLARATION

I declare that I have wholly undertaken the study reported herein under the supervision of Mr.

Emmanuel Yaw Adu Amankwah and that except portions where references have been duly cited, this dissertation is the outcome of my research.

Belinda Agyei-Poku (PG4367715) …………………… …………………..

Student Name and ID Signature Date

Mr. Emmanuel Yaw Adu Amankwah …………………… …………………..

Supervisor‟s Name Signature Date

Mrs. Faustina D. Wireko Manu (PhD) …………………… …………………..

Head of Department Signature Date

ACKNOWLEDGEMENT

I thank the almighty God, whom I serve, for the grace to finish thesis work. My profound gratitude goes to my supervisor, Mr. Emmanuel Adu Amankwah for his tireless, guidance, patience, constructive criticisms, critical comments and suggestions throughout the course of this study. I am grateful to him for his supervision, guidance and support during my research work. Special thanks should go to my family: My husband Thomas Agyei-Poku, children;

Akua, Kwasi, Ama and Kwame Agyei-Poku, my father and mother Ernest and Theresa

Owusu-Badu, sister Brenda Biney, and all my siblings whom I shall always remain grateful for their support, kindness, love, prayers and patience during all the time of the study. My deep sincere gratitude also go to friends Apeku Osborn-Jnr, Williams and Redeemer, all at

KNUST, for their full time support, assistance and kindness during my thesis at Kwame

Nkrumah University of Science and Technology.

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DEDICATION

I dedicate this work to my beloved husband Mr Thomas Agyei-Poku for his love and care. To my children Akua, Kwasi, Ama and Kwame Agyei-Poku so that they become greater scholars who will not only be able to understand different aspects of the world but also to change them in appropriate and positive ways. May Almighty God bless them all, Amen.

ABSTRACT

Fruits of Solanum torvum are generally consumed by lactating and nursing mothers, pregnant women and anemic patients when cooked for medicinal and nutritional purposes. Lack of preservation method has led to its high postharvest losses. However processing methods such as drying can affect differently the nutrient, colour and anti-nutrient content of food samples at different temperatures. This work therefore sought to determine the effects of treatment and different temperatures on the nutritional and anti-nutritional composition of the dried fruits. Proximate composition, some minerals (iron, magnesium, and calcium), anti-nutrients (Alkaloid, Oxalate and Tannin) and colour of the fresh and pre-treated dried samples were determined. AOAC (1995) methods were used for the determination of moisture, fiber, fat and ash content. AOAC (1990) method was used for the determination of protein. Minerals were determined using the Atomic Absorption Spectroscopy methods. Oxalate was determined by titrimetric method, Tannins by the spectrophotometric method and Alkaloids by the Gravimetric method. The results indicate that the fresh fruits possess high moisture content of 78.3% and 82 on wet basis. Fat, fiber, ash and protein contents increased with the exception of carbohydrate which decreased for the dried samples irrespective of the drying pretreatment. Minerals determined increased after drying for all temperatures with the effect of the treatments not well established. Vitamin C decreased after drying with the exception of the berries pretreated with ascorbic acid. Alkaloids and Tannins reduced after drying but oxalate was not affected by heat. Boiling reduced the browning effect with the 5% ascorbic acid treated samples recording the highest range of browning values. The high iron content of the fruits proves the fact that the fruits truly have hematinic property. These present research indicate that Solanum torvum fruits boiled and dried at 70oC has the best nutritional qualities, reduced anti-nutritional properties and a better desirable colour properties.

TABLE OF CONTENTS

DECLARATION...... i ACKNOWLEDGEMENT ...... iii DEDICATION...... iv ABSTRACT ...... v TABLE OF CONTENTS ...... vi LIST OF TABLES ...... ix LIST OF FIGURES ...... x

CHAPTER ONE…………………………………………………………………………………………….…………….………1 1.0 INTRODUCTION ...... 1 1.1 Background ...... 1 1.2 Problem Statement and Justification ...... 5 1.3 Significance of the study ...... 6 1.4 Main objective ...... 6 1.5 Specific objectives...... 6 1.6 The scope of the study ...... 7 1.7 Limitation of the study ...... 7

CHAPTER TWO ...... 8 2.0 LITERATURE REVIEW ...... 8 2.1 Introduction ...... 8 2.2 Origin of solanum torvum ...... 8 2.3 The Solanum torvum plant ...... 9 2.4 Varieties ...... 10 2.5 Health benefits...... 11 2.6 Nutritional composition of Solanum torvum ...... 13 2.7 Cuisine ...... 13 2.8 Food Preservation ...... 14 2.8.1 Drying...... 14 2.8.2 Fundamentals of Drying ...... 15 2.8.3 The Drying Process ...... 16 2.8.3.1.1 Mechanism of Drying...... 17

2.9 Oven Drying ...... 17 2.9.1 Batch Drying Ovens ...... 18 2.9.2 Conveyor Drying Ovens ...... 18 2.9.3 Specialty Drying Ovens ...... 18 2.10 Nutritive values of dried vegetables ...... 19 2.10.1 Types of food to dry ...... 19 2.10.2 Equipment for drying ...... 19 2.10.3 Pre-treatment before drying...... 19 2.11 ANTI-NUTRIENT ...... 21 2.11.1 Oxalates ...... 23 2.11.2 ALKALOIDS ...... 23 2.11.3 Tannins ...... 24 2.12 BROWNING Index ...... 25

CHAPTER THREE………………………………………………………………………………………………..………S….26 3.0 MATERIALS AND METHODS ...... 26 3.1 Source of materials ...... 26 3.1.1 Sample preparation ...... 26 3.2.0 Laboratory Experiment ...... 28 3.2.1 Moisture determination ...... 28 3.2.2 Crude protein determination ...... 28 3.2.3 Crude fiber...... 29 3.2.4 Crude fat determination ...... 30 3.2.5 Ashing ...... 31 3.2.6 Mineral analysis ...... 31 3.2.7 Determination of Vitamin C ...... 32 3.3 Anti-nutrients ...... 32 3.3.1 Oxalate Determination ...... 32 3.3.2 Alkaloids DETERMINATION ...... 32 3.3.3 Tannin CONTENT determination ...... 33 3.4 Effect on Colour ...... 33 3.5 DATA ANALYSIS ...... 34

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CHAPTER FOUR ...... 35 4.0 RESULTS AND DISCUSSION ...... 35 4.1 Proximate composition ...... 35 4.2 Mineral Composition...... 38 4.3 Vitamin C contents ...... 41 4.4 Antinutrient concentrations ...... 42 4.4. Drying curves ...... 46 4.5 Browning Index ...... 47

CHAPTER FIVE ...... 51 5.0 CONCLUSION AND RECOMMENDATION ...... 51 5.1 Conclusion ...... 51 5.2 Recommendation ...... 51

REFERENCES ...... 52 APPENDIX 1 ...... 62

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LIST OF TABLES

Table 4. 1 Proximate composition of Solanum torvum fruits dried under different temperatures and pretreatments ...... 38

Table 4. 2 Mineral and Vitamin C contents of Solanum torvum fruits dried under different temperatures and pretreatments ...... 42

Table 4. 3 A composition of Solanum torvum fruits dried under different temperatures and pretreatments ...... 45

Table 4. 4 Colour measurements of Solanum torvum fruits dried under different temperatures and pretreatments...... 49

LIST OF FIGURES

Figure 1: Flow chart for blanched, unblanched and boiled fruit of Solanum torvum (Modified from Kingori et al., 1999)...... 27

Figure 2 Moisture content (Kg[water]/Kg[dry mater] as a function of drying time at different temperatures of boiled and ascorbic acid treated turkey berry (Solanum torvum) fruits...... 47

CHAPTER ONE 1.0 INTRODUCTION

1.1 BACKGROUND

The Solanum torvum (Solanaceae) plant is a common plant native to many tropical countries in Africa and the West Indies. It is also found in some parts of Asia. The leaves are used in many traditional medical practises in Africa (Adjanohoun et al., 1996). The plant grows as a short (about 2 - 4 m tall), erect shrub with lots of branches. Solanum torvum grows into a large thorny impenetrable thicket (Mohan and Bhandare, 2012). Some other species, which belong to the genus Solanum, are Solanum ficifolium and Solanum ferrugineum (Langeland and

Burks, 1998).

The fruits of Solanum torvum are collection of little greenish and spherical with diametrical length of about 1 centimeter. Their greenish appearance turns yellowish when they are fully ripen and has a very thin flesh with so many seeds that are flattened. They are thin-fleshed and contain numerous flat, round, brown seeds (Little et al., 1974; Howard, 1989; Liogier, 1995).

Mineral nutrition is a significant aspect of human life and it plays a vital role for healthy growth. These nutritional minerals have various sources. In many African countries, wild edible plants are used as food and hence contribute significantly to the nutritional needs of the people. In Ghana, Solanum torvum (locally referred to as ‘Kwahunsusua’) is used essentially for food. In the south of Ghana, especially, it is added to palm nut soup and some stews. It is a general belief in the Ghanaian culture that the fruit of Solanum torvum is rich in minerals that help boost the amount of blood in the human body, hence, it is generally recommended by locals to take the juice of Solanum torvum to prevent anaemia. The fruit is well known for its tremendous nutritional value and supplementary role as tonic and haemopoietic agents. It is also used for the treatment infections like jigger wounds as well abscesses. Dermatophilosis in animals, ringworm and athlete’s foot in man are also been remedied with Solanum torvum.

(Chah et al., 2000). It is used in the treatment of stomach pain and skin infections (Siemonsma and Piluek, 1994). It possesses antimicrobial (Ajaiyeoba, 1999; Chah et al., 2000), antiviral

(Arthan et al., 2002), anti-oxidant (Sivapriya and Srinivas, 2007). Cardiovascular and anti- platelet aggregation activities (Nguelefack et al., 2008). Solanum torvum contains a number of potentially pharmacologically active chemicals like isoflavonoid sulfate and steroidal glycosides (Yahara et al., 1996; Arthan et al., 2002). Fluid concentrates of solarnum torvum pose a deadly risk to various species like mice. They turn deadly by shrinking erythrocytes quantity as well as leukocytes and Platelets in their blood (Tapia et al., 1996).

According to Akoto et al. (2015) the dried fruits of Solanum torvum possess very high moisture content (86.230%), with carbohydrates amounting 7.033%, proteins contributing

2.322%, fat deposits 0.278%, 0.143% of ash and crude fiber contributing 3.993%. They also did analysis for essential metal contents and had following results were attained; iron contributing 76.869mg/kg, manganese contributing 19.466 mg/kg, calcium 221.583 mg/kg, copper contributing 2.642 mg/kg and zinc contributing 21.460 mg/kg. In the determinations of the vitamins, 0.078mg/100g and 2.686 mg/100g were obtained for vitamins A and C respectively. There was similar study conducted in India, proximate composition analysis revealed a lower moisture percentage (80.5 %) but much higher ash content (12.3 %). Iron, copper and manganese were found to be below 0.5 μg/mL (which is equivalent to mg/kg).

Calcium was the most abundant mineral as well in that study (Bhagyashree et al., 2012).

Alternative work was also done on anti-nutrients by Pramodini and Uday (2015) which revealed a higher oxalates content of (6.08±0.83), tannins (0.067±0.004) and saponin

(0.06±0.03).There was similar work performed by Pérez-Amador et al., (2007) of which the alkaloid content was (0.12%). According to Karmakar et al. (2015) the ascorbic acid in the fresh fruits is (24.64g/100g). Also similar work was done by Ajay et al. (2012) of which the fruit possess (37.4mg/100g) ascorbic acid.

Drying is a primordial process used to preserve and prolong shelf life of various food products

(Ratti, 2001). The removal of moisture prevents the growth and reproduction of microorganisms and minimizes many moisture-mediated deteriorative reactions. It brings about substantial decrease in volume and weight, diminishes packing, storage, transportation costs and permits storage ability of the product under ambient temperatures (Mujumbar,

1995). However, drying results in structural, chemical and phytochemical changes that can affect quality properties such as texture, colour and nutritional values (Maskan, 2000;

Attanasio et al., 2004; Scala et al., 2008). These sensory characteristics of vegetables that are texture, colour, taste and aroma are considered very important parameters in the drying quality of vegetables, and they may strongly influence consumer acceptance of these food items.

Changes in texture in dry foods are often dramatic because of the membrane disruption and the associated loss of turgor.

According to Salunkhe et al. (1991) the colour of fruits and vegetables can easily be changed due to the enzymatic and non-enzymatic reactions. He further said, browning, lipid oxidation, colour loss and change of flavor in foods can occur during drying and storage. Enzymatic browning of foods is undesirable because it develops undesirable colour and produces off flavour. These can be prevented through pre-treatment such as the application of heating

(blanching), sulphur dioxide or sulphites and acids which can help vegetables to retain it colour.

Several drying methods used for various products include air, oven, solar, microwave, smokehouse and freeze drying. In the Ghanaian community, the most preferred method is solar drying. For the purpose of this research oven drying will be used.

Solar drying technology appears to be one of the most possible options to reduce the postharvest losses (Wiriya et al., 2009). Nonetheless, drying of the fruits at very high temperatures

could destroy the flavour, colour and nutrients of the dehydrated products (Praveenkumar et al., 2006)

Drying foods with oven is seen as the simplest and cheapest way because it doesn’t use any specialized equipment and it is also a faster as compared to the sun drying. Oven drying produce more uniform, hygienic and attractively coloured dried product (Doymaz, 2004). As indicated by Ogunlakin et al. (2012), stove drying techniques have better impact on dietary and utilitarian properties of cocoyam flour than coordinate sun or sunlight based drying strategy.

According to Vega et al. (2009) air-drying and oven drying are favoured due to processing cost and efficiency. However, air drying has drawbacks of both long drying time required and poor quality. Fruits, vegetables and their dried products are good sources of energy, minerals and vitamins. However, during the dryness process, there are changes in nutritional quality

(Sablani 2006). There are vitamins such as A, C and thiamine that are sensitive to heat as well as to oxidative degradation vegetables. Sulphuring can destroy thiamine and riboflavin while pre-treatments such as blanching and dipping in sulphite solutions reduce the loss of vitamins during drying.

The human body needs a good amount of fiber to provide it with minerals and vitamins like thiamine, riboflavin and niacin in order to function properly and these are largely found in fruits and vegetables like peas, corn, peppers, zucchini, onions, okra, tomatoes, millet, carrot and green beans (Troftgruben, 1977). Although consumption of fresh unprocessed plant food is widely advocated, evidence is emerging that in vivo bioavailability of many protective compounds are enhanced when vegetables are dried. Mohan et al. (2009) utilized dried products of Solanum torvum to know the impact it will have on pulse and metabolic modifications in fructose hypertensive rats and announced that ethanolic concentrate of

Solanum torvum treatment essentially diminished systolic circulatory strain and other metabolic parameters in fructose model of hypertension. Likewise Mohan et al. (2010) used dried fruits of S. torvum to know the effect on doxorubicin-induced nephrotoxicity in rats and reported that Solanum torvum has the potential in preventing the nephrotoxicity induced by doxorubicin. Sivapriya and Leela (2007) utilized dried seeds of Solanum torvum for their examinations on Isolation and decontamination of a novel cell reinforcement protein from the water concentrate of Sundakai (Solanum torvum) seeds and announced that a novel protein from the water concentrate of Sundakai seeds is a magnificent cancer prevention agent.

However, the method used is unknown. Karmakar et al. (2015) who used sun as an initial preservation after which oven method for drying the fruit of Solanum torvum for their project.

The rest failed to mention the type of drying methods used for drying the Solanum torvum.

1.2 PROBLEM STATEMENT AND JUSTIFICATION

From the above information, there has been mixed reports, whereas drying has been done on other products but on Solanum torvum is scanty. Many researchers use dried fruits of Solanum torvum but they failed to mention the type of drying methods used. Meanwhile Solanum torvum fruit is widely consumed vegetable in Ghana. It is a seasonal crop and mostly available on the market in its fresh and raw state but not the dry one leading to high spoilage rate.

Considering the fact, that most Ghanaian homes use it in preparing soups and other sauces due to the high nutritional content; it would be very much appreciated if it is available all year round. The challenge here is how to treat it in order to preserve it for a longer period and most importantly, retain most of its nutrients during the preservation process.

The most preferred preservation process utilized for vegetables and fruits is drying; either oven or using the sun’s heat. Whichever method employed involves the use of some level of heat and as already mentioned the application of heat to vegetables destroys most of their nutrients such as the B and C Vitamins. This study therefore seeks to identify the effects of

drying method on the nutritional and anti-nutritional values of Solanum torvum and the possibility of oven drying the Solanum torvum fruits so it can be made available all year round.

1.3 SIGNIFICANCE OF THE STUDY

There has been literature indicating some studies conducted on Solanum torvum fruits with emphasis only on the nutritional content of the fresh sample. Mention can be made of Akoto et al. (2015) as mentioned in the literature. Chah et al. (2000) decided the antimicrobial movement of methanolic concentrate of Solanum torvum natural product. Arthan et al. (2006) worked on Furostanol glycoside 26-O-β-glucosidase from the leaves of Solanum torvum.

From literature, different drying method and effect on its nutritional composition of vegetables especially the vitamins C have not been reported. This work seeks to investigate the effects of treatment and different temperatures of oven drying method on the nutritional and anti- nutritional content of Solanum torvum. An attempt is thus being made to make the fruits which are perishable, available all year round.

1.4 MAIN OBJECTIVE

To determine the effects of pre- treatment and different temperatures of oven drying method on the nutritional, anti-nutritional values and colour properties of the fruits of Solanum torvum

1.5 SPECIFIC OBJECTIVES

1. To determine the proximate, mineral and anti-nutrient composition of fresh and dried

Solanum torvum at different oven temperatures.

2. To determine the effect of temperature on colour and some heat labile vitamins such as

vitamin C of pretreated and untreated Solanum torvum fruits.

1.6 THE SCOPE OF THE STUDY

The study lies within finding out drying effects on nutritional as well as anti-nutritional value in Solanum torvum fruit. It will also be used as a means of curing diseases in our present country, since Solanum torvum is highly nutritious vegetable with a lot of medicinal values.

Finally, the study recommends the use of Solanum torvum be in fresh or dry state, since it is cheap and easy to come by.

1.7 LIMITATION OF THE STUDY

Financial constraints in laboratory work and also some chemicals and equipment needed to perform the work was major problems for the research.

CHAPTER TWO 2.0 LITERATURE REVIEW

2.1 INTRODUCTION

A lot of research work has been done on solanum torvum in several countries including

Ghana. There is more information on it as a top health food, ways of using it on menu and pharmacological area. There is, however, not much information on effect of drying on the nutritional and anti-nutritional composition in solanum torvum, therefore this chapter will investigate the various works that have been done on solanum torvum and also whether pretreatment and drying has effect on solanum torvum fruit.

2.2 ORIGIN OF SOLANUM TORVUM

The Solanum torvum (Solanaceae) plant, a common plant is geographically traced from

Florida through southern Alabama and West Indies thus Mexico through Central and South

America through Brazil. The plant is also found in numerous tropical nations in Africa (Little et al., 1974). It is additionally found in a few sections of Asia.

With just a modest number in the calm zones, there are around 2000 types of Solanum on the planet that are for the most part appropriated in the tropical and sub-tropical regions, (Jennifer et al., 1997). It is a little Solanaceous bush appropriated generally in Pakistan, India, Malaya,

China, Philippines, and tropical America (Nasir, 1985) and has around 21 species and one assortment in this sort is utilized for home grown drug (Hu et al., 1999). Pharmacological investigations show that the stem and foundation of S. torvum have hostile to tumor, against viral, hostile to bacterial, mitigating, and other restoratively crucial impacts. Among the major chemical components of S. torvum are steroids, steroid saponins, steroid alkaloids, and phenols. In Ghana, the solanum torvum is acquired from various forest zones especially in the

Ashanti, Brong-Ahafo, and certain parts of central region and also in the backyards of most homes.

Solanum torvum was widely naturalized in the hotter beach front areas in north and east of

Australia (Batianoff and Butler, 2002). It was perhaps at the same time naturalized in the beach front areas northern New South Wales and in Tropical Africa, Asia and southeastern

America (Cowie and Kerrigan, 2007).

2.3 THE SOLANUM TORVUM PLANT

Solanum torvum grows as a short (about 2-4 m tall), erect shrub with lots of branches and into large thorny impermeable undergrowth (Mohan and Bhandare 2012). The fruits of Solanum torvum are groups of little green berries (around 1 cm in breadth) that end up noticeably yellow when completely developed. The fruits come in various levels of thin skins, rounded in shape with darker seeds (Little et al., 1974; Howard 1989; Liogier 1995). Solanum torvum grows every year in height around 0.75-1.5m. The plant may be killed by within two years by bushes at which stage pruning wouldn’t even help it survive (IPIF, 2007).

According to (Little et al, 1974), the solanum torvum plant is usually 2 or 3m in height and

2cm in basal diameter, but may reach 5m in height and 8cm in basal diameter. The shrub usually has a single stem at ground level, but it may branch on the lower stem.

The stem bark is gray and nearly smooth with raised lenticels. The inner bark has a green layer over an Ivory color while the roots are white. According to Tu Forest and Kim Starr, Starr

Environmental, turkey berry is a broadleaved, evergreen shrub that can grow to about 16 ft.

(4.9 m) in height. The stems are armed with stout, straight, or lightly curved prickles (Van

Brakel, 1978).

According to the USDA (2007), the more youthful stems are green or purplish in shading and now and then meagerly canvassed in thistles of about 3-7mm. More established stems end up plainly darker or greenish-dark colored and in the long run lose their covering of hairs.

The similarly huge, on the other hand orchestrated leaves are usually borne on stalks of 1 - 5 cm long and the leaves are extensively egg-molded in layout (i.e. applaud) or practically adjusted fit as a fiddle with whole to shallowly-lobed edges. In any case, the leaves of more youthful plants might be all the more profoundly lobed (i.e. pinnatisect).

Whenever exhibited, the tips leaf and flaps might be pointed or adjusted and that of grown-up plants don't have any prickles. The seedlings and youthful plants may have some little prickles on their upper surfaces. More so the surface and whitish undersides, are shrouded in star- molded hairs. Likewise the little, white blossoms happen in huge, spread groups. Plants bloom ceaselessly in the wake of achieving a stature of 3.3 to 4.9 ft. (1 to 1.5 m).

The flowers of the plant sprout in bunches on a single stalk of about 2-17mm long holding about 15-100 flowers on a single stalk with about five white petals (9-12 mm long), combined at the base with green sepals of about 2.5-6 mm.

As indicated by Bostock and Holland (2007), the plant is viewed as ecological weed in

Queensland, and lately recorded as a need ecological weed in no less than one Natural

Resource Management locale.

2.4 VARIETIES

There are other species which belong to the genus Solanum, and they are, Solanum ficifolium,

Solanum ferrugineumgiant, Solanum chrysotrichum, Solanum lycocarpum, Solanum grandiflorum, Solanum bahamense of Carl Linnaeus (as var. persicifolium) Solanum chrysotrichum of von Schlechtendal (as var. pleiotomum) Solanum ferrugineum (as var. ferrugineum, var. hartwegianum) Solanum lanceolatum of Cavanilles (as var. schiedeanum)

Solanum macaonense (as var. lasiostylum), Solanum rudepannum (as var. fructipendulum, var. ochraceo-ferrugineum), Solanum scuticum (as ssp./var. brasiliense, var. daturifolium, var. genuinum) (Langeland and Burks, 1998).

2.5 HEALTH BENEFITS

In Ghana and many other countries, the fruits and leaves are used for food and many traditional medical practices respectively (Adjanohoun et al., 1996). Solanum torvum are utilized as a part of conventional drug as tonic and haemopoietic operators and for the treatment of torments. Generally in the North-West Province of Cameroon, the juice of natural product is utilized for the treatment of jigger wounds, abscesses, skin contaminations, for example, ringworm and competitor's foot in man and dermatophilosis in creatures

(Siemonsma and Piluek, 1994). Research shows that the natural products contain phytoconstituents, for example, steroid glycosides and saponins, settled oil; vitamin B gathering; vitamin C; press salts: saponins and steroidal alkaloids.

In Ghana, a few sections of the plant have been utilized either as a haemostatic after labor or as a wellspring of saponin for the hemi union of cortisone and sex hormones or for exacerbating tranquilizers, diuretics or stomach related tonics. Its organic products are utilized as a part of the treatment of weakness, wounds, snakebites, inciting lactation, and as hors d'oeuvres though the leaves are utilized as a part of the treatment of stomach torment, whitlow, colds and whooping hack.

It has pain relieving and calming (Ndebia et al., 2007), antimicrobial (Ajaiyeoba, 1999; Chah et al., 2000), antiviral (Arthan et al., 2002), antiulcer (Nguelefack et al., 2008a), immuno- secretory (Israf et al., 2004), anti-oxidant (Sivapriya and Srinivas, 2007), cardiovascular and anti-platelet aggregation properties. S. torvum contains a number of pharmacologically active chemicals like isoflavonoid sulfate and steroidal glycosides (Yahara et al., 1996; Arthan et al.,

2002). For a long time, diverse ethnic gatherings have utilized the dried stem and foundation of this plant for treatment of different illnesses. Its Chinese therapeutic name is Jinniukou.

As indicated by Chah et al. (2000), the methanol concentrate of S. torvum natural product exhibited intriguing development restraining action against microscopic organisms generally connected with pyogenic contaminations. The watched exercises may offer a help for a portion of the employments of the organic product squeeze in ethnomedicine.

Diabetes mellitus is a standout amongst the most genuine unending infections around the world. It is caused by ceaseless hyperglycemia and creates alongside increments in stoutness and maturing in the general populace. (Lord et al., 1998). One of the therapeutic methods to decreasing postprandial hyperglycemia is to retard the absorption of glucose by the inhibition of carbohydrate hydrolyzing enzymes -amylase and glucosidase in the digestive organs. The fruit of Solanum torvum is an inhibitor of sucrose and maltase. Screening experiments for rat intestinal glucosidase (sucrose and maltase) inhibitors in 325 plants cultivated in Japan’s southern island, Tanegashima, marked reserve against both sucrose and maltase in the extract of the fruit of Solanum torvum.

Yahara et al. (1996) indicates that solanum torvum fruits are moderate inhibitors against glucosidase which provides a prospect for anti-diabetics. In any case, S. torvum displayed some level of cell reinforcement action and DNA repair ability on oxidative DNA harm caused by free radicals (Abas et al., 2006).

In a distributed novel, protein was disconnected from the water concentrate of S. torvum seed and that ended up being successful cell reinforcement, even at low measurement, when contrasted with prestigious standard manufactured cancer prevention agents (Sivapriya and

Srinivas, 2007). Be that as it may, fluid concentrate of S. torvum uncovers intense calming and pain relieving properties (Ndebia et al., 2007). In Ghana, the leaves are utilized to treat frosty; the natural products are utilized to upgrade the hemoglobin in pregnant ladies, lactating moms and people experiencing sickliness.

2.6 NUTRITIONAL COMPOSITION OF SOLANUM TORVUM

Solanum torvum is composed of the following vital minerals and nutrients which are very supportive in curing and averting diseases. Vitamin A, Iron (24.5 mg), Calcium (0.28 mg), Fat

(1.7 mg), Fiber (56.9 mg).

According to Akoto et al. (2015), the fruits of Solanum torvum possess very high moisture content (86.230%), carbohydrates 7.033%, proteins 2.322%, fats 0.278%, ash 0.143% and crude fiber 3.993%. They also did an analysis for essential metal contents and had following outcomes; iron 76.869mg/kg, manganese 19.466 mg/kg, calcium 221.583 mg/kg, copper

2.642mg/kg and zinc 21.460mg/kg. In the determination of the vitamins, it contains

0.078mg/100g and 2.686 mg/100g for vitamins A and C respectively.

There was similar study conducted in India where proximate composition analysis revealed a lower moisture percentage (80.5 %) but much higher ash content (12.3 %). Iron, copper and manganese were found to be below 0.5 μg/mL (which is equivalent to mg/kg or ppm).

Calcium was the most predominant mineral as well in that study (Bhagyashree et al., 2012).

2.7 CUISINE

The green crisp organic products are utilized as a part of Thai food as a fixing in specific curries or crude in certain bean stew glues (nam phrik)

(http:/www.thaitable.com/Thai/Ingredients/2. pea eggplant.htm). In Tamil Nadu, India, The natural product is expended specifically, or cooked as nourishment in Tamil Nadu, India. The fruits of solanum torvum have much medication significance as in Siddha medication; one of the conventional frameworks of India is utilized to enhance assimilation. In Ghana, it is used for preparing soups such as palm nut soup, groundnut soups, light soup, green soup

(abunabunu). It is also used to prepare stews such as “nkontomire” (spinach), garden eggs stew among others.

2.8 FOOD PRESERVATION

Food Preservation is a process of retaining food over a period without being contaminated by pathogenic organisms or chemicals and without losing its flavour, colour, texture, and nutritional value. The reasons for preserving food are the availability of food, and also to obtain different types of food at different locations. According to Rahman (2007), food preservation is very important for food safety and security. Unsuitable preservation and storage methods cause losses of food which range from 10 to 30% for cereals and 50 to 70% for fruits. Methods of food preservation are as follows; solar drying, heat processing, dehydration, chemical preservation, smokehouse drying, canning, pasteurization, oven drying, and freeze drying.

2.8.1 DRYING

Drying is a mass exchange process comprising of the evacuation of water or another dissolvable by dissipation from a strong, semi-strong or fluid. This procedure is regularly utilized as a last generation venture before offering or bundling items. For an item to be viewed as "dried", the last item should be strong, as a nonstop sheet (e.g. paper), long pieces

(e.g. wood), particles (e.g. corn chips or oat grains) or powder (e.g. sand, salt, washing powder, drain powder). A wellspring of warmth and an operator to evacuate the vapor delivered by the procedure are frequently included. In bio items like sustenance, grains, and pharmaceuticals like antibodies, the dissolvable to be evacuated is perpetually water

(Greensmith, 1998). Also drying is carried out through the application of heat or at ambient conditions. The product is spread thinly over pavement, tarpaulin or plastic sheet and exposed to the sun when drying under ambient temperatures. Turning has to be completed regularly to avoid sun burns or scorching of product. When the water is forced out of the product, it is termed as dehydration.

Drying can likewise be said to be the most seasoned safeguarding technique. Individuals have been drying sustenance for a huge number of years by putting the nourishment on mats in the sun. The moisture level of agricultural products is decreased between 10-15% to prevent microbial growth or retard activities of enzymes. According to Hartel and Heldman (2012),

Food scientists have found that by reducing the moisture content of food to between 10 and

20%, bacteria, yeast, mold and enzymes are all prevented from spoiling food items.

Be that as it may, this straightforward technique enables the nourishment to be defiled by clean, organisms, airborne molds and bugs, rodents, and different creatures. Moreover, outdoors drying is frequently impractical in muggy atmospheres (DeLong, 1979). There are various sorts of drying strategies including; (sun powered) drying, Oven drying, Freeze drying, Smokehouse drying, Drum drying, Tunnel drying, Microwave drying among others.

The factors that normally affect drying product include the following:

i. Composition of raw material,

ii. Size, shape and arrangement of stacking of produce,

iii. Temperature, relative humidity and velocity of air and

iv. Pressure and heat transfer to surface.

2.8.2 FUNDAMENTALS OF DRYING

Drying includes the evacuation of dampness; this is proficient through the utilization of warmth to the item. The warmth builds the vapor weight of the dampness in the item over that of the encompassing air. The moisture, both liquid and vapour, are caused to move to the surface of the product by pressure and/or thermal gradient. Evaporation occurs and water vapour is transmitted to the surrounding air. Nonetheless, this air may become saturated but the process of drying continues if this moist air is replaced by less saturated air (Fuller, 1991).

2.8.3 THE DRYING PROCESS

When drying food, temperatures ought to be monitored carefully at the beginning and end of the drying period. Drying the fruits is really a difficult task since too low a temperature can allow bacteria to grow on them and too high a temperature could also cook the fruits instead of drying them. At the end of drying period, high temperatures also cause food to burn losing its flavour and nutritive value. High temperatures may be used at the beginning, but essentially, should be reduced as food begins to dry.

The significance of dried foods cannot be overrated. Since the products lose water, they are easy to transport and don’t require any special storage equipment. They have to be stored in a moisture-free environment in order to ensure that the products do not rehydrate after being dried. However drying is generally not difficult, dried foods are tasty, nutritious, lightweight, and easy to store and use. The flavour and most of the nutritive value are preserved and concentrated. In many cases, vegetables, fruits, meat, fish and herbs can all be dried and preserved for several years. Fundamentally there are two disadvantages of drying; the products lose vitamins, and they change in appearance (Troftgruben, 1977).

The kitchens and sustenance stores in any nation will attest the amount and assortment of dried nourishments being used. The evaluations of sustenance are momentous. Dried items are turning into an exceptionally appealing contrasting option to advertising new items. Drying might be required for a few reasons. Right off the bat, water is expelled from the new yield to broaden its helpful life. The dried item is later re-hydrated before use to create a sustenance intently taking after the crisp harvest. Dried vegetables are a case of this drying application.

Furthermore, a product may require drying for additionally handling. For instance, many grains are dried so as to be ground into flour. At long last, new harvests are in some cases dried so another item, particularly not quite the same as its unique shape, can be delivered.

Sultanas, the dried type of grapes, are a case of this drying application. In Ghanaian

communities, the most common preservation method used is drying and to be precise is solar drying. This work seeks to use oven drying.

2.8.3.1.1 MECHANISM OF DRYING

The vitality of the sun is utilized by sun powered dryers to warm the air that streams over the nourishment in the dryer. Warmed air can hold more dampness as its relative moistness diminishes. The dampness vanishes from the surface of the sustenance as warm, dry wind streams through the dryer (Archuleta et al., 1983). The real measure of dampness vanished per unit of time diminishes as the drying continues. The dampness in the outside surface of the sustenance is vanished in the principal period of drying. At that point, dampness from the deepest segment of the material must go to the surface once the external layer is dried in the second period of drying. Due to the diminished cooling impact coming about because of the slower rate of dampness dissipation, overheating may happen amid the second period of the drying procedure. The sustenance will "case solidify" or shape a hard shell that traps dampness inside if the temperature is too high. This can be a source decay of the sustenance.

Expanded wind streams or less warmth accumulation might be alluring with a specific end goal to anticipate overheating amid this bit of the drying cycle.

2.9 OVEN DRYING

Oven drying is the least complex intends to dry nourishment on the grounds that no uncommon hardware is required. It is additionally speedier than sun drying or utilizing a sustenance dryer. Regardless stove drying can be utilized just on a little scale. For the most part, a kitchen stove can just hold 4 to 6 pounds of sustenance at once.

The greatest efficacy and quality comes from using the right oven for the job, and drying ovens come in three core classifications: batch, conveyor, and specialty.

An oven can be used as a dehydrator by merging the factors of heat, low humidity and air flow. Dehydrators are quicker than oven drying because they have an in-built fan for the

movement of air. However, some convention ovens have in-built fans. It takes about twice the time needed to dry food in an oven than it does in a dehydrator. Thus, the oven uses more energy and is not as efficient as a dehydrator (Harrison and Andress, 2000). Oven dried food is more brittle and generally darker than and not as much of flavour as food dried in a dehydrator. Another drawback of oven drying is its energy cost. Test the oven temperature with an oven thermometer for about 1 hour before drying in an oven. The oven must maintain a temperature of 55º C to 65º C. You will not have high-quality dried food if the oven cannot maintain a temperature in this range (Rhee et al., 2003).

2.9.1 BATCH DRYING OVENS

Batch drying ovens are often used by manufacturing companies for drying items of inconsistent sizes, with large bulky objects, or when items need an extended drying time. They also are suitable for processes where production volume is relatively low, and where capital budgets are tight because they are manually loaded and unloaded.

2.9.2 CONVEYOR DRYING OVENS

Conveyor drying ovens are the most efficient and effective solution where manufacturing companies requires inline production or a high volume of items on conveyors, in continuous or indexed stop-and-go motion. Though they usually entail a greater capital investment than batch ovens, conveyor drying ovens have the potential for a substantial yield on investment over time from increased productivity.

2.9.3 SPECIALTY DRYING OVENS

Some categories of manufacturing call for a specialty drying oven designed and constructed from the ground up. Only the requirements of the manufacturing process can determine the precise features and methods to be employed. A few of the types of products that have required specialty ovens are fishing line, powders.

2.10 NUTRITIVE VALUES OF DRIED VEGETABLES

Vegetables are an incredible wellspring of minerals and Vitamins B, for example, thiamine, riboflavin, and niacin. The two foods grown from the ground offer profitable measures of the fiber (mass) that the body needs. The water utilized for splashing or cooking dried sustenance must be incorporated into the arrangement of soups, sauces and flavors. This is because the water is nutrient-rich as it contains the oozed Vitamins of B and C.

2.10.1 TYPES OF FOOD TO DRY

Dried foods that are consumed worldwide include grains such as rice, millet, wheat, sorghum among others.

Fruits like ripe apples, peaches, berries, apricots, cherries, mango, sultanas’ currents, orange, and pears are subjected to drying. Fruits are simpler to dry than vegetables because moisture evaporates more easily. Vegetables, for example, peas, corn, onions, peppers, okra, green beans and tomatoes including flavors, herbs, meat, fish, nuts and drinks, for example, tea and espresso can likewise be dried.

2.10.2 EQUIPMENT FOR DRYING

These equipment helps in making more uniform good product although they are not absolutely necessary: a thermometer to check the broiler temperature, an electric fan to course the air, a sustenance scale to measure nourishment previously, then after the fact drying, a blancher for vegetables and a sulfur box for organic product (Keith, 1984).

2.10.3 PRE-TREATMENT BEFORE DRYING.

The pre-treatment generally improves quality and can make the food safe to eat although many fruits and vegetables may be dried and stores without pre-treatment. It maintains colour, reduces nutrient loss, stop decomposition by enzyme action, ensure more uniform drying and also extend storage life. During storage, decomposition from enzyme action is less a problem

with fruits than it is with vegetables as they have higher sugar and acid, which counteract enzyme action (Harrison and Andress, 2000).

Blanching (heating in boiling water or steam) is the pre-treatment process of choice for vegetables. Virtually all vegetables must be blanched before drying to destroy the enzymes that make vegetables deteriorate. On the other hand, fruits are ordinarily not blanched prior to drying due to their delicate nature and intrinsic acidity (Bruhn et al., 2007). Some fruits and vegetables are blanched by soaking in hot water (95 to 100 °C) or exposure to steam. A fellow

(2009) stipulates that enzymes turn inactive when blanched at 80 oC and stops all life processes. It further cleans and softens vegetables and makes them easier to rehydrate later.

Sulfuring dried fruits must be carefully controlled so that sufficient Sulphur in existent to preserve the physical and nutritional properties of the product all through its anticipated shelf life, but not so large that it undesirably affects flavour (Harrison, and Andress, 2000). In this work, ascorbic acid with different concentrations, steam blanching with different temperatures and boiling was used.

Boiling is a method by which food is cooked in adequate quantity of water. For example we boil potatoes, eggs, rice and vegetables. Usually green leafy vegetables such as cabbage, fenugreek and spinach are cooked without adding extra water. Vegetables such as green peas and green beans are boiled or cooked with a little water.

The significance of boiling can be said safe and simple method of cooking also the food does not get charred. It is suitable for large scale cooking. Boiled food is also digested easily. Some of the drawbacks of boiling includes, water soluble nutrients are lost if the water in which food is boiled is thrown away. Boiled foods are not attractive and at times tasteless. Therefore the taste of boiled food can be improved by adding lemon or other herbs and spices.

2.11 ANTI-NUTRIENT

Anti-nutrients are said to be chemical compound found in plants which work contrary to ideal nutrition needed in humans. These chemical compounds do not allow man to utilize all the nutrients available to him when they are present in the body. Their characteristics pose a major limitation in the use of certain plants as food sources without adequate and effective processing (Akande et al., 2010). These chemicals are known as anti-nutrients or anti- nutritional factors. Although they are not entirely associated with feed and food from plant origin, they are frequently considered to come from plant. These hostile to healthful components are otherwise called auxiliary metabolites that are created as side-items to the typical essential metabolites that the plant needs. Anti-nutrients are also known to be generated through mechanisms such as inactivation of nutrients, diminution of the digestive process or the metabolic utilization of feed or food (Gemede and Ratta, 2014). According to

Khokhar and Apenten (2003), these anti-nutritional factors are synthesized as part of the plant’s defence against attack by herbivores, insects and pathogens as well as a ways of survival during unfavourable growth conditions. They are used by the plants to protect themselves and prevent them from being eaten up by predators (Inuwa et al., 2011). There are numerous anti-nutritional factors and these include saponins, tannins, phytates, alkaloids, flavonoids, enzyme inhibitors, oxalates, cyanogenic glycosides, protease inhibitor, lectins and goitrogens. Anti-nutrients can block the absorption of nutrients and can act as toxins in the body. Numerous hostile to supplements are contained in grains, vegetables (counting soy) and white potatoes. Gluten, a protein found in many grains, is a protein hostile to supplement that can devastate unobtrusive or gigantic destruction on different frameworks of the body, even without celiac malady. Strategies for de-enacting these against supplements incorporate maturing, growing and drenching. Hostile to supplements, for example, Saponins in white potatoes are negligibly adjusted by warmth, and afterward cause a provocative response in the

small digestive organs, where the lion's share of supplement ingestion happens. This incendiary response not just pieces assimilation, it can cause "defective gut", which at that point enables other lethal atoms to rupture the intestinal boundary and enter our circulatory system. (Cheikin, 2012).

Some of these plant chemicals have been shown to be harmful to health or obviously useful to human and animal health if consumed at exact amounts. (Gemede and Ratta, 2014). The most useful antinutrients are phytate, tannins, protease inhibitors, calcium oxalate and lectins.

According to Shahidi (1997) these antinutritional factors use adverse or beneficial health effects through the same mechanisms and that these effects are dependent on the concentrations present. He proved that these effects can be manipulated through their concentrations in order to take advantage of the useful aspects in the management of chronic diseases. Many of the anti-nutrients like phytates, lectins, phenolic compounds and tannins, saponins, enzyme inhibitors, cyanogenic glycosides and glucosinolates have been reported to reduce the availability of certain nutrients, inhibit digestive enzymes, increase the production of gases in the colon, impair hydrolytic functions and transportation at the enterocyte site, form precipitates and complexes with nutrients and minerals limiting their availability and accessibility and impair growth. Others such as phytoestrogens and lignans have also been linked to induction of infertility in humans (Nair et al., 2012). Recorded among the beneficial effects of According to (Shahidi, 1997; Khokhar and Apenten, 2003).these antinutritional factors have the aptitude to reduce blood glucose and/or plasma cholesterol and triacylglycerols. In the interim, phenolic compounds from plant sources, phytic acid, protease inhibitors, saponins, lignans and phytoestrogens have been demonstrated to reduce cancer risks and possess anti-inflammatory and antimalarial properties. Due to these properties, they are becoming of increasing interest in the pharmacology, nutrition, medical and biochemistry.

Examples of anti-nutrients found in food materials include, Oxalates, phytates, saponnins, alkaloids and Tannins.

2.11.1 OXALATES

Oxalates are a salt framed from oxalic corrosive cases incorporate, Calcium Oxalates, which is observed to be in plant life. Solid ties are shaped among oxalic corrosive with different reserves, including Calcium, Magnesium, Sodium, and Potassium. These compound mixes frame Oxalates salts. A few Oxalates salts are dissolvable, for example, sodium and potassium though calcium Oxalates salts are fundamentally insoluble. These insoluble calcium Oxalates has a tendency to hurry in the Kidneys or in the Urinary tract, molding sharp-edged calcium

Oxalates valuable stones when the levels are adequately high. These pearls help in the advancement of kidney stones game plan in the urinary tract when the destructive is released in the urine. Oxalates are an anti-nutrient which under normal conditions is restrained to separate compartments. However, when it is processed or digested, it comes into contact with the nutrients in the gastrointestinal tract (Noonan et al., 1999). Oxalic acid, when released, binds with nutrients, rendering them inaccessible to the body. If food containing some amounts of oxalic acid is consumed regularly, nutritional deficiencies are likely to occur and severe injury to the lining of the gut (Gemede and Ratta, 2014).

2.11.2 ALKALOIDS

Alkaloids are little natural particles that are created by plants from amino acids. The amino acids are decarboxylated to create amines which thusly respond with amine oxides to shape aldehydes. The aldehyde and amine bunches consolidate to shape a trademark heterocyclic ring. The idea of this ring fills in as methods for ordering alkaloids. For instance, when the glycone parcel is glycosylated with a starch moiety, it is ordered a glycoalkaloid. Alkaloids are known to be one of the greatest gatherings of concoction mixes orchestrated by plants that are by and large present as the salty acidic concentrates of plants, for instance, citrus extracts 23

from oxalic, malic and tartarics. Alkaloids are available in around 15-20 percent of every single vascular plant and are comprised of a few rings of carbon with side chains with at least one of the carbon molecules supplanted by nitrogen. They are bitter metabolic by-products and these accounts for their potential toxicity and ability to wade of insects and other plant eating animals (Rodriguez and Tecson-Mendoza, 1998). Alkaloids act on the nervous system to disrupt or increase electrochemical transmission in very undesirable ways. One of the subclasses of Alkaloids is the tropane alkaloids and utilization of these high tropane alkaloids will cause loss of motion, fast heartbeats and in serious cases, may prompt demise. Another alkaloid subclass is the tryptamine alkaloids, high doses of which lead to staggering gate and death. Different activities of alkaloids in people are interruption of the cell layer in the gastrointestinal tract and manifestations of neurological issue (Gemede and Ratta, 2014).

2.11.3 TANNINS

The term Tannins alludes to the utilization of tannins in Tanning creature stows away into cowhide; be that as it may, the term is broadly connected to any huge polyphenolic compound containing adequate hydroxyls and other appropriate gatherings to shape solid edifices with proteins and different macromolecules. Tannins have atomic weights going from 500 to more than 3000. Tannins are known to be steady with diminishing protein absorbability among species, either by hiding stomach related chemicals. They hinder the exercises of trypsin, chymotrypsin, amylase and lipase, diminish the protein and also invade dietary iron ingestion,

(Felix et al., 2000). They are responsible for lessened reinforce utilization, advancement rate; maintain adequacy and protein absorbability in test animals. If tannins center in the eating regimen ends up being too high, microbial impetus practices including cellulose and intestinal preparing may be disheartened. Moreover, tannins shape insoluble structures with proteins and the tannins-protein buildings may be responsible for the counter nutritious effects of tannins containing foods, (Gemede and Ratta, 2014)

2.12 BROWNING INDEX

The procedure of nourishment turning darker inferable from the compound responses that happen inside is called Browning. There are various differing ways sustenance synthetically changes after some time; cooking falls into two fundamental gatherings these are enzymatic and non-enzymatic procedures. The searing procedure of sustenance may deliver alluring or bothersome outcomes, contingent upon the type of food. Kaanane.et al (1989).

Enzymatic caramelizing is a standout amongst the most essential responses that happen in many products of the soil and in fish. These procedures influence the taste, shading, and estimation of such sustenance, Holderbaum, (2010).

As per (Osanai et al., 2003; Hosoda et al., 2005) enzymatic searing has been measured utilizing caramelizing markers through a biochemical record, for instance utilizing polyphenol oxidase movement. (Yam et al., 2004).also said physical markers in light of shading, CIE

L*a*b* shading space has been the most widely utilized shading reference, because of the uniform dispersion of hues and on the grounds that it is near human view of shading.

Browning Index is a parameter that is used to determine the occurrence of Brown-colored compounds in product (Bal et al., 2011). It can be used a yardstick to determine the quality of particular reference food product. So as to do a nifty gritty portrayal of the shade of a nourishment thing and along these lines all the more accurately assessed its quality, it is important to know the shading estimation of each purpose of its surface. Be that as it may, at introduce accessible business colorimeters measure L*a*b* facilitates just finished a not very many square centimeters, and in this manner their estimations could be not exceptionally illustrative in heterogeneous materials, for example, most nourishment items (Papadakis et al.,

2000)

CHAPTER THREE

3.0 MATERIALS AND METHODS

3.1 SOURCE OF MATERIALS

Fresh samples from Solanum torvum plant were gotten from local market specifically Agogo markets in Kumasi. The equipment used was force-air oven (BINDER GmbH Germany),

Muffle furnace (ThermoLYNE F48010-33 USA), Goveh crucible, Soxhlet apparatus and

Kjeldahl (KJELTEC SYSTEM 1026 Sweden), electronic balance, desiccator and tongs. The chemicals were Analar grade and obtained from department of food science and technology and the central laboratories of KNUST.

3.1.1 SAMPLE PREPARATION

The Solanum torvum fruits were remove;d from the stalk, well washed with clean running water and then wiped with clean kitchen cloth to dry all the water around it. The average dimensions of fresh fruit ranged between 2.3 - 4.5cm diameters. The three methods of treatment were blanching, boiling and ascorbic acid treatment. To steam blanch, a water bath with a tight fitting lid and a colander that hold the food to at least 3 inches above the bottom of the water bath was used. About an inch or two of water was put into the water bath and the water brought to different temperatures 50, 60 and 70°C respectively. As soon as the water reached it various temperatures Thermometer was inserted in the water to determine the various temperatures, the samples (100 gramms) (weight or number of samples) were placed in the colander in a single layer so that the steam reaches all parts of the sample. The water bath was covered and timed till the samples were completely blanched. For the boiled samples, the fruits 400 gramms (weight) were placed in cold water and was covered and boiled at (100°C) for 5 minutes and the water drained. The sample was allowed to dry for 8 minutes.

Hot air dryer was used. The fruits were then weighed (electronic balance) to 100 grams for each treatment. Three 100 g each sample (triplicates), were distributed evenly in single layer on a perforated sample tray, and placed in a hot air dryer (model and country of make) for uniform distribution of air and temperature The samples were air dried at temperatures of 50 ,

60 and 70oC. The weight of drying sample was measured within 5 minutes using electronic balance of 0.01g accuracy (model and country of make). The weight was taken at 1h intervals for 4h, and then 2h intervals for 4 and subsequently at 6h intervals till the end of drying. The dried specimen was permitted to cool at room temperature and moved into a cooler at 4°C out of a zip bolt sack till additionally analyzes were directed. Drying was continued until the sample reached the desired moisture level of 10% (wet basis). Figure 1 shows the flow diagram of procedure for the blanched, unbalanced and boiled fruit before drying.

Figure 1: Flow chart for blanched, unblanched and boiled fruit of Solanum torvum (Modified from Kingori et al., 1999).

3.2.0 LABORATORY EXPERIMENT

Laboratory work was carried out in the Laboratory of Food Science and Technology, KNUST.

Moisture, Ash, Fat, Protein, Fibre, Carbohydrate, Iron (Fe), Magnesium (Mg), Calcium (Ca),

Tannins, Oxalates and Alkaloids were determined.

3.2.1 MOISTURE DETERMINATION

The level of moist was calculated by the Association of Official Analytical chemist (AOAC)

1995). Two grams (2 g) of fresh samples was accurately weighed in a clean (crucible) of a known weight. It was immediately put in a conventional oven at 105 °C for 6 h. The crucible were then put inside desiccator over a period of 30 minutes and allowed to cool. Afterwards, the crucible with its content was weighed. The percent moisture was then calculated using the following formula: % moisture = W2 − W3 × 100W2 − W1

Where: W1 = Weight of crucible,

W2= Weight of crucible + slices,

W3 = Weight of crucible + dry sample.

3.2.2 CRUDE PROTEIN DETERMINATION

The protein content was determined by the Association of Official Analytical chemist

(AOAC) (1990).Two grams (2 g) of the sample were weighed into a digestion tube. Five grams (5 g) of catalyst and 1 glass bead together with 10 mL concentrated sulfuric acid was also added. Digestion tubes were placed in the digester. Digestion commenced initially at a temperature of 400ºC in order to avoid bubbling and boiling to achieve a clearer solution. An

Erylenmeyer flask of measure (250 mL) containing 50 mL of 4% boric acid was placed in distillation unit for 10 min with the condenser tip extended below the surface of the acid solution. A 100 mL water as well as 70 mL (50% sodium hydroxide) excess was added to the

digests during the distillation process to ensure complete release of ammonia. Titration on the distillate with standardized 0.1 M hydrochloric acid until pinkish colorization was obtained.

Result was noted to the averaging 0.05 mL volume and calculated nitrogen and hence protein content

%Total Nitrogen

= 100 × 푠푎푚푝푙푒 푡푖푡푟푒 푣푎푙푢푒 − 퐵푙푎푛푘 푡푖푡푟푒 푣푎푙푢푒 × 0.1

× 0.01401sample weight × 10

% Protein = %N × 6.25

3.2.3 CRUDE FIBER

The crude fibre content was determined by the Association of Official Analytical chemist

(AOAC) (1995).Five (5) grams of sample was taken from the zip lock bags and defatted using the AOAC standard before subjecting to analysis. Two (2) g of Solanum torvum samples were weighted into a flat bottom flask and 200 mL of boiling sulphuric acid (1.25%) was added for

30 min. The resulting solution was filtered through cheese cloth using a funnel and then washed with hot water until it was free from the acid. The residue on the cloth was transferred into a flask and 200 mL of boiling sodium hydroxide solution (1.25%) was added. The flask was immediately connected to the digestion apparatus and boiled for 30 min. The flask was then removed and immediately the followed by filtration of the solution rinsed thoroughly with distilled boiling water. The residue was rinsed with 15 ml of alcohol. It was transferred into porcelain crucibles and dried at 105°C in an oven for 24 h. It was cooled to room temperature in a desiccator and weighed. The cauldron and its weight were burned in a mute heater at 550°C. It was cooled to room temperature in a desiccator and weighed. The difference between the two weights was recorded and the percentage crude fiber calculated as

3.2.4 CRUDE FAT DETERMINATION

The crude fat content was determined by the Association of Official Analytical chemist

(AOAC) (1995). A soxhlet extractor was utilized for dissolvable extraction of the oil. The dissolvable (pet ether) was expelled from the concentrate by refining and the lingering oil part gathered and utilized for investigative work. Dried examples from the dampness examination was weighed, pressed in a whatman channel paper and embedded into the soxhlet extractor. A

40-60ºC oil ether (BDH analar review) was utilized as the extraction dissolvable. The time of consistent extraction was 6 hours. Toward the finish of this period, the dissolvable was recouped by straightforward refining and the lingering oil was dried in a broiler at 105ºC for 2 hours and cooled in a desiccator and permitted to cool, before being weighed. The drying, cooling and weighing was repeated until a constant dry weight was obtained. The extracted oil sample was in a well-sealed dark brown coloured glass bottle and kept for analytical test

3.2.5 ASHING

The ash content was determined by the Association of Official Analytical chemist (AOAC)

(1995).Clean empty crucible was placed in a muffle furnace at 600°C for an hour. It was cooled in a desiccator and then weighed (W1). Sample of about 1.0 g was weighed (W2) and transferred into the crucible. The example was lighted over a burner with the assistance of blowpipe, until scorched. At that point the cauldron was put in a suppress heater at 600°C for

6 hours for finish oxidation of all natural issue in the specimen. After the procedure, cauldron was cooled in the desiccator and the weight was noted W3. Percent rough fiery remains was computed and recorded as

% Ash = (W3 − W1) × 100W2 − W1

Where: W1 = Weight of porcelain crucible,

W2= Weight of porcelain crucible + slices,

W3 = Weight of porcelain crucible + Ash.

3.2.6 MINERAL ANALYSIS

Mineral analysis for Iron (Fe), Magnesium (Mg), and Calcium (Ca) were done by using

Atomic Absorption spectrophotometer (AAS) and Association of official Analytical chemist

(AOAC) (1990).About 1 g of the sample was weighed and 10-20 ml of nitric acid was added.

The solution was digested till the volume reduced to almost half. About 10 ml sulphuric acids was added and digested until white fumes appeared and the solution cleared. About 10-20 ml of nitric acid was added and digested until the solution cleared. The arrangement was set in the instrument where it was warmed to vaporize and atomize the minerals. A light emission was gone through the atomized test, and the ingestion of radiation was measured and particular

wave lengths comparing to the mineral of intrigue. The sort and convergence of the minerals introduce was acquired by measuring the area and power of the crests in the retention spectra.

3.2.7 DETERMINATION OF VITAMIN C

About 5g of sample was weighed and prepared. 20ml aliquot of the sample solution was pipetted into a 250 ml conical flask and about 50ml of distilled water added. 1 ml iodine solution was also added. Sample was then titrated with 0.005M iodine solution. The endpoint of the titration was identified as the first permanent trace of a dark blue-black colour due to the starch-iodine complex using 1% starch as an indicator. Repetitions were carried out to until concordant results were obtained (titre agreeing within 0.1 ml) (AOAC, 1990).

Ascorbic acid content (mg/100g)

= titre x molarity of titrant x 176.12 x 100weight of sample

3.3 ANTI-NUTRIENTS

3.3.1 OXALATE DETERMINATION

A gram of test was weighed into 100ml cone shaped jar. 75ml 3M H2SO4 was included and mixed for 1hr with an attractive stirrer. This was separated utilizing a Whatman No 1 channel paper. After, 25ml of the filtrate was taken and titrated while hot against 0.05M KMnO4 arrangement until a black out pink shading endured for no less than 30 sec. The oxalate content was then computed by taking 1ml of 0.05m KMnO4 as proportionate to 2.2mg oxalate

(Underwood and Day, 1986)

3.3.2 ALKALOIDS DETERMINATION

Sample of 2g was weighed onto filter paper and transferred into conical flask. 20 mL of 10 % acetic acid solution was added to the sample. This was shaken and allowed to stand for 4h after which it was filtered using a number four filter paper. The filtrate was then evaporated

for 3mins over a hot plate to about ¼ of its original volume. About 10 mL NH4OH (25%) was added drop wise to precipitate the alkaloids. The precipitate was then filtered off with weighed filter paper number one and washed with 1 % NH4OH solution. The precipitate in the filter paper was dried in an air oven at 60°C for 30 minutes and reweighed. The alkaloid content was calculated from the difference in weight between the sample and the precipitated alkaloids

(Harborne, 1973).

3.3.3 TANNIN CONTENT DETERMINATION

Soak about 0.2g of sample in 10ml of 70% acetone and then place in an ice bath. Shake the set up for 12-15 minutes to extract tannin. Allow to cool for about 30min and then filter to collect the supernatant. Place 0.5ml of supernatant in a test tube and add 0.5ml of distilled water followed by 0.5 of foilin’s reagent and 2.5ml of 20% Na2CO3 solution. Vortex the test tube and incubate at room temperature for 40mins.Read the absorbance of the resulting solution at

725nm with a colorimeter and plot a standard tannic acid curve.DM basis (Doss et al., 2011).

3.4 EFFECT ON COLOUR

Tristimulus colour measurements (L*, a* and b* values) were performed using a chromameter

CR-410 (Konica Minolta Inc. Osaka, Japan). The instrument was calibrated with a white reference tile (L*=97.52, a*=–5.06, b*=3.57) prior to measurements. The L* (0=black,

100=white), a* (+red, –green) and b* (+yellow, –blue) colour coordinates were determined according to the CIELAB coordinate colour space system.

Specimen bowl were fully filled with test samples and placed on the blank surface tile measuring unit. The Optical System was placed over the specimen bowl to start the measuring cycle by clicking on the measure button. Each sample was measured in triplicates. All samples were measure at ambient temperature. Result was displayed on the screen on the Chroma

Meter.

Browning Index (BI) was calculated using the measured L*, a* and b* values using the following equations as described by Saricoban and Yilmaz (2010)

BI = 100 (푥 − 0.31)0.17

Where 푥 = (푎 ∗ +1.75퐿)(5.645퐿 ∗ +푎 ∗ − 0.012푏 ∗)

3.5 DATA ANALYSIS

The study was conducted according to a completely randomized factorial design of 3×1 of blanched, unblanched and boiled on drying (oven drying). The experiment was carried out in triplicate and analysis of variance (ANOVA) using Statistical Package for the Social Sciences

(SPSS) version 20 to determine significance of data Statistical significance was denoted at

5%.

CHAPTER FOUR

4.0 RESULTS AND DISCUSSION

4.1 PROXIMATE COMPOSITION

The close composition of solanum torvum fruits dried at different temperatures after boiling and ascorbic acid pretreatments are shown in Table 4.1. The results as displayed in the table clearly reveal that the fruits have very high moisture content. The moisture contents which were determined on the fresh fruits measure at 82.7% after boiling prior to drying and 78.3% prior to ascorbic acid treatment and later drying to an approximate moisture content of 10%.

These values although a little lower, are similar to result obtained by Akoto et al. (2015) for

Solanum torvum fruits from Ghana reported as 86.23% wet basis. Other researchers recorded higher values for different varieties in the solanaceae family. Chinedu et al. (2011) reported

89.27% for Solanum aethiopicum (Ethiopian eggplant) and 92.5% for Solanum macrocarpum

(Gboma eggplant) whereas Sam et al. (2012) mentioned 85.5% for African garden egg

(Solanum verbascifolium), while Edem et al. (2009) gave 74.8%. for Solanum gilo (Scarlet eggplant) This high moisture content and its thin flesh accounts for its low dry matter content, its high perishability (Edem et al., 2009; Chinedu et al., 2011). The moisture contents on dry basis after drying ranged between 0.07% and 0.12%. The samples were dried to approximately

0.1% moisture content (d.b) and no significant differences were observed in these values after drying.

Fat content ranged between 0.16 and 3.08% with the least in the fresh fruit and the highest in the boiled sample dried at 60 0C. It is also evident that the fat content of samples dried at 50 0C are statistically not different from the fresh sample and samples dried at 60 0C and 70 0C

(p>0.05). The influence of the ascorbic acid treatment and boiling prior to drying is not clearly seen here.

The ash content as reported in Table 4.1 ranges between 0.23 and 1.13%. The least ash was recorded in the fresh sample and the highest in the sample boiled and dried at 60 0C. It is seen that the fresh sample is significantly different from the rest of the samples (p<0.05) with the least value as more minerals that were secluded in the cellular parts of the fruits got exposed by the heat from boiling and drying treatments. Samples 705% and 60B are on the other hand not different significantly as well as 50B, 605% and 703% (p>0.05). However, a lot of similarities exist in these values statistically and the effect of pretreatments and temperature on ash content of Solanum torvum fruits is not clearly established in these results. Ash content for

Solanum torvum reported by Akoto et al. (2015) and other authors for other close relating varieties are comparable to the values recorded in the present work. Ash contents give an idea about the inorganic content which comprises the totality of all minerals in the food material.

Samples with high percentages of ash contents are expected to have high concentrations of various mineral elements (Bello et al., 2008). The low mineral contents recorded indicate that

Solanum torvum fruits contain lesser minerals.

The analysis also revealed the protein content of the samples range between 0.41 and 4.03%.

Here also the fresh sample recorded the least protein content contrary to what was observed by

Arinola and Adesina (2014), where boiling and heat treatment reduced protein contents which could be attributed to denaturation of protein and/or solubilization of some nitrogenous compounds during processing of African Walnuts. The sample treated with 3% ascorbic acid concentration and dried at 50 0C recorded the highest. Majority of the samples however were not different statistically (p>0.05). While it is believed that protein content increases after drying due to moisture loss, it is also believed that treatments like blanching can reduce protein contents due to nutrient leaching (Osum et al., 2012), this doesn’t seem to play out well here but it is seen that the fresh has the lowest protein content and the boiled samples had slightly lower protein values although not significantly different which could be attributed to

some protein structures getting broken down by heat to release more detectable nitrogen. The protein content recorded by Akoto et al. (2015) falls within this range. Chinedu et al. (2011) reported similar values of 2.24% and 1.33% for S. aethiopicum and S. macrocarpum respectively.

High fiber content of food materials places a premium on them as excellent source of dietary fiber to be incorporated into low fiber foods to lower cholesterol, prevent constipation and improve digestion (Nwofia et al., 2012). This may be an attribute of these fruits as the fibre recorded is high and ranged between 4.66% and 9.82%. Values recorded by Chinedu et al.

(2011) and Akoto et al. (2015) fell below this range whereas that by Edem et al. (2009) is higher (14.87%, 11.75%). However 4.8% recorded by Sam et al. (2012) for S. verbascifolium falls within the range. According to Chinedu et al. (2011), the high moisture content, and medium range protein and ash values of garden eggs is identifiable with fleshy vegetables which need to stay fresh for market demands. Additionally, the high fiber, low fat and low dry issue might be alluring in the battle against sicknesses, for example, obstruction, carcinoma of the colon and rectum, and artherosclerosis among others.

Carbohydrate determination revealed that the fresh sample contained the highest carbohydrate of 14.56% and the lowest (4.62%) found in the sample boiled and dried at 60oC. There seemed to be no significant observable trend in the carbohydrate results here also. Mahapatra et al.

(2012) reported 11.19% carbohydrate content for Solanum torvum in India falls which is within the range. However, Chinedu et al. (2011) reported values that fall below this range for the two varieties of the Solanum species they worked on. On the other hand Edem et al. (2009) reports values that are way above those recorded in this work.

Table 4. 1 Proximate composition of Solanum torvum fruits dried under different temperatures and pretreatments

Sample MC % Fat % Ash % Protein % Crude Fibre % Carbs % 50B 82.7±0.26a 0.65±0.06b 0.85±0.08bcd 0.96±0.15ab 4.66±0.12a 10.00±0.24bc 503% 78.3±0.00b 0.66±0.05b 0.99±0.03cd 4.03±0.85bc 7.87±1.43bcd 8.15±1.86abc 505% 78.3±0.00b 1.56±0.64ab 0.79±0.11bc 1.28±0.38ab 8.58±1.42cd 9.91±0.06bc 60B 82.7±0.26a 3.08±1.87a 1.13±0.11d 1.27±0.10ab 8.15±1.42bcd 4.62±1.20a 603% 78.3±0.00b 1.44±0.64ab 0.70±0.08b 1.46±0.21ab 6.74±0.65abc 11.36±1.46bc 605% 78.3±0.00b 2.33±1.07ab 0.89±0.06bcd 2.71±0.06bc 8.80±0.19cd 6.96±0.65ab 70B 82.7±0.26a 1.62±0.42ab 1.06±1.17cd 1.24±0.19ab 4.73±0.64a 8.94±0.78bc 703% 78.3±0.00b 1.42±0.33ab 0.90±0.15bcd 1.84±0.27ab 5.61±1.07ab 11.93±1.27cd 705% 78.3±0.00b 3.08±0.19a 1.10±0.06d 0.48±0.27a 9.82±0.11d 7.29±0.11ab Fresh 78.3±0.00b 0.16±0.04b 0.23±0.02a 0.41±0.10a 6.11±0.36abc 14.56±0.33d Values are means ± SD of 3 replications. Means across a column with the same superscript are not significantly different (p≥0.05).

KEY: B=boiled,% =percentage in ascorbic concentration. MC.= Moisture content: Db =dry basis: Carbs=Carbohydrates

4.2 MINERAL COMPOSITION

The mineral and vitamin C content of Solanum Torvum are presented in Table 4.2.

Calcium is a very important mineral in the formation of bones and teeth. Calcium is however recommended for intake from food materials as the use of calcium supplements have been linked with the development of kidney stones formation (Gordon and Vaugham, 1986;

Wardlaw, 1999). Calcium content recorded for S. torvum used in this experiment ranged between 4285 mg/Kg (fresh untreated sample) and 8155 mg/Kg (sample treated with 3% ascorbic acid concentration and dried at 60oC). It is evident from the results however that the calcium contents varied significantly. It is seen for each temperature variation that the contents increased significantly from the boiled in the 3% treated sample and then reduced for the 5% treated sample except for those dried at 70oC. which recorded a reduction in the 3% treated sample before increasing in the 5% treated sample. The observation for the effect of same treatments was different however as Calcium contents in the sample boiled and dried at 50oC

reduced significantly to 4925 mg/Kg for sample boiled and dried at 60oC and then increased to

5930 mg/Kg for the one at 700C. For samples dipped in 3% and 5% ascorbic acid concentration, the calcium contents increased at 60oC and then reduced at 70oC. Calcium can be concluded to be very abundant in S. torvum. Akoto et al. (2015) reported a value of

221.583 mg/Kg for work on S. torvum in Ghana which was very low compared to that which was recorded in this work. However Mahapatra et al. (2012) and Chinedu et al. (2011) recorded 1465.7 mg/Kg for S. torvum in India and 1010.6 mg/Kg for S. macrocarpon and

4984.7 mg/Kg for S. aethiopicum in Nigeria respectively. These values compare with those recorded in this work. Otu et al. (2017) reported an increase in Calcium content when the fresh fruits were dried followed by a significant reduction when the dried fruits were processed to powder.

Neurochemical transmissions and muscular excitability are very important functions in the body that involves magnesium. Many enzyme systems also require magnesium and it plays fundamental roles in phosphate transfer reactions as well. Its deficiency in man however may lead to severe diarrhea, migraines, hyper-tension, cardiomyopathy, arteriosclerosis and stroke

(Appel, 1999; Bamishaiye, 2011). The magnesium concentrations was least in the sample dried at 60oC combined with 5% ascorbic acid concentration treatment. Since it showed no significant difference (p<0.05) from the fresh fruits with a value of 1365 mg/Kg. The highest concentration was recorded in the 3% treated sample dried at 70oC with a value of 5550 mg/Kg. The other values showed significant differences pointing an effect of temperature and treatment applied. It is seen that for all samples dried at 50oC, the concentrations increased significantly from the boiled one to the 5% treated sample in that order whereas for samples dried at 60oC and 70oC, the concentration in the 3% treated samples decreased significantly before increasing again in the 5% treated sample. When same treatments are considered, the temperature effect is also seen as a reduction in Mg concentration for drying at 60oC followed

by a significant increase in samples dried at 70oC. Values available in literature according to

Edem et al. (2009) and Chinedu et al. (2011) were far lower than those recorded in this work.

Iron is an indispensable mineral in the body when processes such as haemoglobin production and oxygenation of red blood cells, digestion and circulation among many others are carried out in the human body. For its function in haemoglobin production, it’s mostly required in the diet of pregnant women, nursing mothers, infants, convulsing patients and the elderly to prevent anaemia and other related diseases (Oluyemi et al., 2006; Bamishaiye et al., 2011).

The results indicate that Iron was the most concentrated in the sample boiled and dried at

70oC. The least was recorded again in the fresh sample with 13.05 mg/Kg concentration. The results show significant differences between all samples analyzed (p<0.05). No particular trends were observed as Iron contents reduced significantly from 67.44 mg/Kg in samples boiled and dried at 50oC to 41.35 mg/Kg in sample treated with 3% ascorbic acid concentration before increasing to 48.26 mg/Kg in sample treated with 5% ascorbic acid concentration. For samples dried at 60oC, Iron contents reduced in 3% treated sample and further losses were observed for sample treated with 5% ascorbic acid. Samples dried at 70oC showed same trend as those dried at 50oC. Similar trends were also observed when same treatments were compared. Similar results were reported by Akoto et al. (2015), Mahapatra et al. (2012) and Otu et al. (2017). However, very low values were recorded by Chinedu et al.

(2011) and Sam et al. (2012). These trends observed also agree with several writers who reported that most minerals especially Iron and Calcium concentrations in many foods increase with heat treatments such as boiling and drying. The difference between the iron content of the fresh and boiled or dried at elevated temperatures can be attributed to heat effect. At higher temperatures, the minerals are released from the cells of the food material

(Esayas, 2009; Bamishaiye et al., 2011).

4.3 VITAMIN C CONTENTS

The results show the highest Vitamin C content in the fresh sample with a value of 31.54 mg/100g and the least 4.47mg/100g in sample boiled and dried at 70oC. It is observed that there were no significant differences (p>0.05) between the samples except for the fresh sample and samples treated with 3% and 5% ascorbic acid concentration and dried at 50oC. It is also evident that temperature affected vitamin C content of the fruits as increasing temperature for each treatment reduced vitamin C concentrations. For example, for boiled samples, 6.50 mg/100g recorded for sample dried at 50oC decreased to 5.47 mg/100g for sample dried at

60oC and further down to 4.47 mg/100g for sample dried at 70oC. At the same temperature, it is also observed that the concentration of ascorbic acid used in the pretreatment had an effect on the amounts determined after the drying process. At 60oC, the concentrations increased from 5.47 mg/100g for the boiled sample to 9.51 mg/100g for sample treated with 3% ascorbic acid concentration breefore increasing further to 9.71 mg/100g. Same trend is observed for

70oC except for 50oC where sample treated with 3% ascorbic acid concentration rose in concentration about three times (3X) to 18.42 mg/100g in the boiled before reducing to 10.69 mg/100g in 5% treated sample. It was expected that ascorbic acid treated samples will retain more ascorbic acid after the drying process but was not the case as the treated samples still had less concentrations significantly different from that of the fresh. This could be due to the fact that ascorbic acid remained on the surface of the fruits and was easily degraded by the heat over the long periods of drying. Although there were no significant differences between the samples dried at 60 oC and 70 oC, the boiled samples recorded the least concentrations which can be attributed to the fact that Vitamin C is water soluble. During the boiling process prior to drying, the vitamin leaches into the water and gets oxidized to form dehydroascorbic acid which is actually reversible. Upon further heating, the product undergoes irreversible conversions into 2,3-diketo-L-gulonic acid (diketogulonic acid) before breaking down into L-

threonic acid and finally into Oxalic acid where the Vitamin C properties are lost (Borsook et al, 1937). This resulted in the low concentrations recorded in the boiled samples. These trends are in agreement with reports that processing and cooking/heating degrades vitamins. Kaleem et al. (2016) reported that vitamin C content of fruit juices decrease with increasing temperature. Esayas (2009) reported that boiling decreases most minerals and vitamin C in fruits and vegetables. Igwemmar et al. (2013) also reported significant effects of heating on

Vitamin C contents of some vegetables in Nigeria and concluded that as heating time increases, the percentage loss of vitamin C increases. According to literature, Akoto et al.

(2015), recorded 2.686 mg/100g whilst Otu et al. (2017) recorded 2.86 mg/100g and 1.83 mg/100g for fresh and dried S. torvum fruits respectively. These values however are lower than that recorded in this work.

Table 4. 2 Mineral and Vitamin C contents of Solanum torvum fruits dried under different temperatures and pretreatments

Sample Ca mg/Kg Mg mg/Kg Fe mg/Kg Vit C mg/100g 50B 6610±42.43f 2630±70.71d 67.44±0.07h 6.50±1.28a 503% 7770±14.14h 3260±28.28f 41.35±0.07b 18.42±5.67b 505% 5070±14.14c 4960±28.28g 48.26±0.00c 10.69±0.95ab 60B 4925±49.50bc 2220±14.14c 55.74±0.01e 5.47±1.32a 603% 8155±49.50i 3125±35.36f 50.01±0.01d 9.51±0.45a 605% 7150±42.43g 1280±42.43a 41.35±0.07b 9.71±2.07a 70B 5930±70.71d 2850±14.14e 76.08±0.01i 4.47±0.28a 703% 4815±77.78b 5550±42.43h 58.71±0.02f 9.52±2.22a 705% 6425±35.36e 1660±28.28b 63.05±0.01g 9.67±0.89a Fresh 4285±7.07a 1365±35.36a 13.05±0.01a 31.54±7.38c Values are means ± SD of 3 replications. Means across a column with the same superscript are not significantly different (p≥0.05).

4.4 ANTINUTRIENT CONCENTRATIONS

The value recorded for the alkaloid content of the fresh sample is 446.10 mg/100g as shown in

Table 4.3 which is the highest among all the samples. The least however was recorded in the sample boiled and dried subsequently at 50oC with a value of 24.76 mg/100g. This is an approximately 94% reduction in alkaloid content in the fresh sample. It is also observed that

the samples boiled prior to drying had the least alkaloid concentrations which increased slightly with an increase in the temperature of drying. This implies that boiling has a significant effect on the alkaloid contents of dried Solanum torvum fruits. It is also observed that among the treated samples, the highest concentrations were recorded in the 3% ascorbic acid concentration treated samples followed by the 5% treated samples The effect of drying temperature on alkaloid contents was not seen as all the samples had similar values except those that were boiled before drying, whose values were lower. This simply suggests that alkaloids are soluble and most are lost to the water used in boiling before subsequent losses during drying. The drying reduced alkaloid contents significantly from the fresh sample.

These agree with Rodriguez and Tecson-Mendoza (1998), who propounded that alkaloids in plant materials can be removed completely by soaking in warm water at 60oC for 60 minutes.

Although significant reductions were observed due to the boiling and drying, it is worthy to note that these values do not go below the toxicity limit for alkaloid consumption as reported by Inuwa et al. (2011) as 20 mg/100g. According to them, when diets containing alkaloids beyond 20 mg/100g is consumed, the deleterious effects of alkaloids will be experienced.

Some of which include paralysis, rapid heartbeats and in severe cases, possible death, as well as symptoms of neurological disorder (Gemede and Ratta, 2014). On the contrary, Mcdonald et al. (1995) reported that the safe level for alkaloids in animal feed is 60 mg/100g. This means that the samples boiled prior to drying can safely be used in animal feeds without causing harm to the animals.

Tannin contents recorded in this work ranged between 31.12 and 511.57 mg/100g with the least recorded in sample treated with 3% ascorbic acid concentration and dried at 50oC and the highest in the fresh sample. The tannin content in the fresh fruit although high, it is lower than that recorded in unpublished work by Boatemaa (2017) for Solanum torvum in KNUST,

Ghana as 632.61 mg/100g (unpublished) and Pramodini and Uday (2015) as 6700 mg/100g.

This value is however higher than values recorded for Solanum melongena by Agoreyo et al.

(2012) and Solanum aethiopicum by Eze and Kanu (2014). It is also observed that among the treated samples, the highest values were recorded for the boiled samples. Although boiling brought significant reductions in the tannin contents from the fresh one which agrees with

Arinola et al. (2014) who observed significant decrease in tannin contents when African walnuts were boiled, it was expected that the least values will be recorded in the boiled samples instead as according to Felix and Mello (2000), tannins are soluble in water but heat stable. The toxicity level for tannins as reported by Inuwa et al. (2011) is 3 mg/100g. This indicates that tannin content reductions obtained in this work is not enough as samples still contain levels far above 3 mg/100g. When diets containing high levels of tannins are consumed, they bind proteins and inhibit digestive enzymes, cause stomach irritation, nausea, vomiting, and liver damage. (Gemede and Ratta, 2014). However, it has been established through studies that plants that have high levels of tannin are used for pharmaceutical purposes because tannins have antidiarrheal and antimicrobial activities (Amabeoku, 2009) and this could explain the traditional medicinal uses of Solanum torvum.

Oxalate content in the fresh fruits of Solanum torvum is the least among the determined antinutrients with a value of 361.66 mg/100g. However, it is evident from the results that boiling and the other treatments did not reduce the oxalate contents as they did for tannins and alkaloids. For oxalates, the least value was rather recorded in the fresh sample with significant increases recorded for the samples boiled before drying and the samples treated with 5% ascorbic acid concentration prior to drying. All samples treated with 3% ascorbic acid concentration prior to drying were not significantly different from each other and the fresh sample (p>0.05). This agrees with observations by Musa and Ogbadoyi (2012) who observed that only sun drying had no significant effect on oxalate contents of vegetables considered.

Nupo et al. (2013) also observed that blanching and drying had no significant effect on oxalate

and tannin contents of Solanum nigrum. Ilelaboye et al. (2013) observed that cooking and cooking after blanching brings significant reductions in oxalate and tannin contents of vegetables. On the contrary, oxalate contents recorded in this work increased with boiling and drying. This can be explained with the fact oxalates are normally secluded in compartments in the plant parts and get exposed to nutrients when processed or digested (Akande et al., 2010).

It is only reasonable therefore to assume that oxalates which could not be detected in the fresh sample got exposed during boiling and drying. Boiling may not have reduced oxalate contents if the oxalates present are more of the insoluble type. The maximum tolerable limit of oxalate is 2000-5000 mg/100g according to Munro and Basir (1969). This implies that oxalate contents of both dried and fresh Solanum torvum poses no risk to consumers. The high levels in the dried samples may however be exploited in the management of cancer as the reduction in calcium bioavailability which results from high oxalates is desirable in starving cancer cells.

Table 4. 3 Anti-Nutrient composition of Solanum torvum fruits dried under different temperatures and pretreatments

Sample Alkaloids (mg/100g) Tannins (mg/100g) Oxalates (mg/100g) 50B 24.76±0.32a 175.76±0.85g 1394.12±2.12e 503% 99.65±0.21d 31.12±0.39a 388.67±14.86a 505% 92.29±10.62cd 39.04±0.42b 387.17±16.98a 60B 29.57±0.31a 179.00±1.10h 1323.59±4.24d 603% 99.04±0.66d 56.60±0.07c 411.18±16.98a 605% 81.22±3.16bc 59.46± 0.30d 562.75±2.12b 70B 33.37±1.29a 179.64±0.20h 1437.64±25.47e 703% 99.75±0.28d 105.01±0.41e 376.67±14.86a 705% 77.21±3.74b 127.67±0.22f 946.92±2.12c Fresh 446.10±0.47e 511.57±0.46i 361.66±14.86a Values are means ± SD of 2 replications. Means across a Colum with the same superscript are not significantly different (p≥0.05).

4.4. DRYING CURVES

In drying, it is important to manage the operating parameters in order to be able to predict the performance of the drying process. This is enabled through mathematical modeling of the drying process which is essential to set out accurate models to simulate the drying curves under different drying conditions. The description and prediction of the drying kinetics of a given material is still a weakness in the modeling of drying process. Drying kinetics is generally evaluated experimentally by determining the moisture ratio through measuring the weight of a drying material as function of time (Fudholi et al., 2012).

Clearly from the Figure. 2, influence of drying temperature and type of pre-treatment on the moisture content as a function of drying time is reported. It is clear that the dampness content declines ceaselessly with drying time. As can be seen from the information exhibited, the time required to dry turkey berry natural products from a scope of 3.6-4.8 to a scope of 0.07-0.12

(db) dampness content diminished with increment in temperature (Figure 2). Generally for all samples, the boiled samples had the highest drying rate, followed by the 3% and 5% concentration ascorbic acid treated samples in that order. For all the treated samples (boiled and ascorbic treated), temperature had a strong influence on the rate of water removal. At

70oC and for different treatment, the drying time for the samples was 6 hours while that of the

3% and 5% concentration ascorbic acid treated sample were 14 and 18 hours respectively.

Boiling is proven to disrupt texture of food materials thereby allowing easy migration of water to the surface of the sample from the center. Chemical treatments modify the surface characteristics of food materials sometimes through case hardening where it becomes difficult for moisture migration into the surrounding air suggesting why the low rate of drying for the

3% and 5% ascorbic acid treated samples.

It is evident from the drying that there isn’t a constant rate time, but gradual reducing rate of drying was present and pronounced at end of drying. The drying behavior happens to be in

line with findings by (Massamba et al., 2012; Minaei et al., 2011; Ekow et al., 2013). Mass transfer of drying sample was rapid during the first early hours of drying. This suggests that the higher the moisture content in a sample the faster the rate of water transport from the inner part to the surface.

4.5

3.5 50B 60B 3 70B 2.5 503% 603% 2 703% 505% 1.5 605%

Moisturecontent/(Kg[water]/Kg[dry mater] 1 705%

0.5

0 0 10 20 30 40 50 60 Drying time/hrs

Figure 2 Moisture content (Kg[water]/Kg[dry mater] as a function of drying time at different temperatures of boiled and ascorbic acid treated turkey berry (Solanum torvum) fruits.

4.5 BROWNING INDEX

Browning Indexes (BI) in ascorbic acid treated samples were significantly higher than samples which were boiled prior to oven drying to 0.1% moisture content (db) (p<0.05). At constant ascorbic acid concentration influence of temperature on BI was not remarkable and not clearly defined. However, temperature strongly influenced the BI of boiled samples. Temperature was negatively related to BI. This clearly shows that the time of exposure of the food material to heat to reduce the moisture content to a certain predetermined moisture content also greatly affect browning. For boiled samples, the time of exposure at 50, 60 and 70oC were 23, 14 and

7 hours respectively while that of 5% ascorbic acid concentration treated sample were 54, 30 and 18 respectively. The BI of sample boiled prior to drying at 50oC was 16.31. This was reduced by 50% to 8.44 when dried at 60oC and further reduced to 5.04 when dried at 70oC this clearly shows that ascorbic acid is not suitable for reducing browning in Turkey Berry at

5% concentration. On the other hand boiling that inactivates some browning enzymes and further drying at higher temperature (70oC) for a shorter period is appropriate for reducing browning in Turkey Berry. Ascorbic acid has been used extensively in preventing enzymatic browning in fruits and vegetables such as reported by Jokić Stela et al. (2009) for apples but this assertion is not the case in this present work. Heat treatments such as blanching has been used to prevent browning and also to maintain texture in fruits and vegetables (Gudapaty et al., 2010; Ong and Law, 2011; Prajapaty et al., 2011). In addition to maintaining the texture, heat treatment effectively inactivates enzymes, however lower or non-thermal treatment is needed as a substitute to keep the fresh-like colour and texture of fresh cut fruits and vegetables (Rico et al., 2007; Shivahare et al., 2009, Gonzalez-Cebrino et al., 2012).

Table 4. 4 Colour measurements (browning index) of Solanum torvum fruits dried under different temperatures and pretreatments.

Temperature Time Pre-treatment Browning Index p-value 50 54 hours 5% Ascorbic acid 26.290.40 0.0001 concentration 23 hours Boil 16.311.23 60 30 hours 5% Ascorbic acid 30.110.32 0.0001 concentration 14 hours Boil 8.440.01 70 18 hours 5% Ascorbic acid 30.360.40 0.0001 concentration 7 hours Boil 5.041.01 values are meanstandard deviation.

4.6 SUMMARY

The proximate composition of the fruits of Solanum torvum plant as determined in this work clearly shows that the fresh fruits have very high moisture contents between 78.3% and 82.7% on wet basis. The least fat percentage of 0.16% was recorded in the fresh fruit and the highest in the boiled sample dried at 60oC which indicates as well a significant increase in fat contents when water is removed from food materials. The ash percentage also follows a similar trend as the fat content which also records an increase when the fruits are dried. The major nutrients protein and carbohydrates recorded were high in the dried samples and lower in the fresh one.

Fiber contents were also very high on weight basis as moisture loss concentrates more nutrients and fiber

The results from the mineral analysis showed that Calcium is the most abundant mineral in the fruits of Solanum torvum, followed by Magnesium among the three minerals analyzed. Iron contents were very low. Drying seems to concentrate minerals in a way as the dried samples recorded increases in the case of all minerals.

The effect of temperature on Vitamin C was clearly seen in the determinations of Vitamin C on the samples. The highest content was recorded in the fresh sample which reduced

drastically in the dried samples. Ascorbic acid treatments did not preserve Vitamin C contents in any way. However, the lower temperatures recorded less destruction of Vitamin C as observed in the samples treated with 3% and 5% ascorbic acid concentration and dried at 50

0C.

Anti-nutrient concentrations were very high in the samples of Turkey berry (solanum torvum) fruits used in this work. Boiling and drying were seen to have significant effects on the anti- nutrient concentrations. Boiling and drying reduced alkaloid and tannin contents in the dried samples as compared to the fresh sample. However, these concentrations were still higher than stipulated toxic levels which implies that the consumption of both fresh and dried turkey berry fruits may pose health challenges associated with diets containing high alkaloids and tannins.

On the hand, boiling and drying increased the oxalate contents of the fruits although not to levels beyond the toxic level. The highest increments were obtained in the samples boiled prior to drying and this is attributed to boiling exposing oxalates secluded in cellular compartments which could not be detected in the fresh sample.

It can be concluded from the drying curves that, the moisture content decreases continuously with drying time. As such, the time required to dry turkey berry fruits decreased with an increase in temperature. It is observed that the boiled samples dried faster than the treated samples with the fastest drying sample being the sample boiled and dried at 700C which dried in less than 10hrs. 3% and 5% ascorbic acid treated samples which were dried at 50oC were found to be the slowest drying samples with drying time above 50 hrs.

Browning indexes (BI) in ascorbic acid treatment samples were significantly higher than samples which were boiled prior to oven drying (p<0.05) and so can be concluded that, heat treatment in the form of boiling is the most successful in preventing excessive browning in the dried samples as it is proven to effectively inactivate enzymes as well.

CHAPTER FIVE 5.0 CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION The proximate composition shows that Solanum torvum is a good source of important nutrients such as protein, fiber, carbohydrate and fat. The dried samples had higher amount of minerals such as calcium, iron and magnesium than that of the fresh samples. However, there was a significant reduction in anti-nutrient such as tannins and alkaloids with the exception of oxalate, which was significantly and possibly affected by boiling. There was a decrease in vitamin C with increased boiling temperature while treatment did not show any specific trend on vitamin C at constant temperature. Boiling as a pre-treatment factor helped to retain the green colour of solanum torvum especially when dried at 70°C. This was better than the ascorbic acid pre-treatment. Drying at 70°C reduces drying time while maintaining most nutrient.

5.2 RECOMMENDATION

Since pre-treatment of boiling and dried at 70 °C retained the green colour of solanum torvum it is recommended that further work should be done with the focus on packaging the dried powdered fruits and establishing the shelf life of the final products.

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APPENDIX 1

METHODS USED IN PROXIMATE ANALYSIS

% moisture = (W2 − W3) × 100W2 − W1

W1=weight of dish, W2= weight and wet samples, W3= weight of dish and dry sample, where weight of moisture = W2-W3.

% Ash= (W3 − W1) × 100W2 − W1

Weight of ash (W3) = W1-W2,

W1=weight of crucible and sample before incineration, W2=weight of crucible and sample after incineration, W4=weight of sample transferred to crucible.

% Crude Fibre =

(weight of sample before ashing weight of sample after ashing) x 100weight of flour sample

% crude fiber = W3 × 100W4

Weight of fiber (W3) = W1-W2,

W1=weight crucible and sample and asbestos after incineration,

W2= weight of crucible and sample and asbestos after incineration

% total nitrogen= 100 x VA − VB × NA × 0.01401W X 10

Therefore % protein= % total nitrogen x factor

VA = Volume in ml of standard acid used in nitrogen, VB= volume in ml of standard acid used in blank,

NA=normality of an acid used (HCI), W=weight of sample in grams.

Total carbohydrate =100-(crude protein +moisture +crude fat +ash +crude fiber).