Intermediate Moisture Dr Aparana Sharma Assistant Professor ( Science) JNKVV-College of Agriculture, Ganj Basoda, Distt- Vidisha; MP [email protected] Introduction Water plays an important role in all types of food products. Be it raw or cooked, fresh or dried, fruits & vegetables or cereals & pulses, raw or cooked or preserved, veg or non- veg, liquid or solid; all kinds of food products contain a specific amount of water which is responsible for its texture, taste, mouthfeel and most important is its shelf-life. However, scientifically speaking moisture content of the food differs from water activity in the food. On one hand where the moisture content of the food is responsible for the nutritional content and sensory attributes of the food, water activity is considered responsible for microbial load or the shelf stability of the food itself. Free water in fruits and vegetables is the water available for chemical reactions, to act as a transporting medium for various compounds and also to support microbial growth. In bound form, also called the osmotic bonding, it is available with , , gums etc. Intermediate Moisture Foods (IMF)- The concept National Center for Coordination of Research on Food and Nutrition, France during 1980’s proposed a comprehensive definition for Intermediate Moisture Foods as, “Food Products of soft texture, subjected to one or more technological treatments, consumable without further preparation and with a shelf stability of several months, assured without thermal sterilization, nor freezing or refrigeration, but an adequate adjustment of their formulation; composition, pH, additives etc and mainly water activity O (aw) which must be between 0.6 and 0.84 (measured at 25 C).” Technically speaking, Intermediate Moisture Foods or food products are those which have water activity (aw) between 0.75-0.92 (Welti-Chanes et al., 1997). This water activity of these products is adjusted in the given range by using different preservation methods viz., dehydration, osmotic dehydration and dry infusion. Although different sources report varying water contents for IMF’s, the water content between 20 and 50 per cent may be accepted as the intermediate moisture level which makes the fruits soft, moist and ready to eat (Cemeroglu, 1986). aw (Water activity) Water activity is a thermodynamic property which is defined as the ratio of in a food system and vapour pressure of pure water at the same temperature. It is the ratio between the vapour pressure of the food itself, when in a completely undisturbed balance with the surrounding air media, and the vapour pressure of distilled water under identical conditions. Pure water has an aw of 1 . Free water in fruits and vegetables is the water available for chemical reactions, to support microbial growth and to act as a transporting medium for compounds. There exists a relationship between ‘Equilibrium Relative (ERH)’ and water activity (aw) and is equally important because of the common factor ‘Vapour Pressure’. Where, ERH is defined as the relative humidity of the air surrounding the food at which the product is in equilibrium with the environment, i.e., it neither gains moisture nor loses it. A saturated solution of sodium chloride has a water activity of 0.755 and this same concentration of solution in a closed container will develop an equilibrium relative humidity (ERH) in a head space of 55.5 per cent. Hence the relationship at the same vapour pressureis given as; ERH aw = ------100 The water activity of 0.80 means that the vapour pressure is 80 per cent of that of pure water at that particular temperature. Also, the water activity increases with rise in temperature. Foods with water activity around 0.95 or more provides sufficient moisture to support the growth of spoilage organisms including bacteria, yeasts and molds. Most of the spoilage causing organisms grow in a apecific moisture condition and thus is referred to as critical water activity, below which growth cannot occur. Intermediate Moisture foods have water activity values in a range of 0.65 to 0.90. Fig.1indicates the range of water activity for various types of food products, where the water content is also important.

Source: Elisavita Sandulachi. 2012.

Intermediate Moisture Food is an age old concept of in which traditional ingredients were just added to food to achieve specific water activity (aw) while maintaining the sufficient water content for acceptability and palatability of food products. With the advancement in the field of Science and Technology involving food and increased concern of food scientists towards reducing spoilage of food products, new ingredients namely humectants and preservatives have been used in the development of new IMF’s. it is important to understand that IMF’s take into account both water activity (aw) as well as moisture content of the food and thus sometimes the range of water activity (between 0.6-0.9) and moisture content (between 10-50 per cent) varies amongst a wide range. Many other factors including pH, Eh (electrical potential/ redox), F (High temperature), T (Low temperature) values, use of preservatives, micro flora etc also affect the preservation quality of food products including IMF’s. Different preservation methods viz., dehydration, osmotic dehydration and dry infusion may be used to adjust water activity during the preparation of IMF’s. Water content of such products may vary between 20-50 per cent to get an acceptable intermediate moisture level in products which are softer, moist and ready to eat (Cemeroglu, 1986). Different preservation methods that can be used to reduce the water activity in food products are categorized as: 1. Partial drying: It is the simplest and cheapest method of food preservation, ‘sun drying’. In most parts of the country open sun drying is still practiced for drying fruits, raisins, fish and similar type of food products. However, on commercial levels, large sized dehydrators, ovens and dryers can be used to reduce the water content and to control the water activity (aw). 2. Osmotic drying (Moist infusion): This method of drying is based on the principle of ‘osmosis’ in which different humectants, eg., sugars, , alcohols, polyols, organic acids and proteins etc are used. The difference in the osmotic pressure of the food and the solution used acts as the driving force between the two components. Thus, water in the food material diffuses into solution and humectants diffuses into food material. This method is used in the preparation of candid foods and preserves where is used as a humectant. 3. Dry infusion: This method is recommended for the preparation of high quality of dehydrated preserved products. This is also an energy intensive method of dehydration where fruits are first dehydrated and then soaked in required humectants until the desired water activity is achieved. 4. Blending or formulation: This is the most recent method of dehydration and its ease of use makes it more popular amidst food producers. Here, the food is mixed with required ingredients including humectants and the food mixture is applied to required cooking, baking or extrusion technique to achieve the required water activity in the final product. It is time saving, energy efficient and more flexible method to get a desired type of product including preserves, confectionery items, snacks and pet foods. Types of Intermediate Moisture Foods: The main purpose of IMF is to get the desirable water activity in the final product besides maintaining enough moisture content in the final product to ensure its palatability and . The technique is very useful in the preservation of fruits and vegetables without refrigeration. Use of sugar or salt as humectants helps to achieve the desired water activity as they act as water activity depressant. Also, addition of preservatives provides the margin of safety against spoilage organisms making these foods stable even at room temperature. Some of the examples of IMF’s include:  Murabba  Candied fruits/veg/rhizome/fruit peel  Crystallized fruit  Jam, jellies, marmalade  Dehydrated fruits  Dehydrated vegetables  Raisins  Dates  Seedless tamarind  Dried apricots  Dates paste  Safety of intermediate Moisture Foods The principle and technique for the preparation of Intermediate Moisture Foods is very reliable as it provides margin of safety against the spoilage causing . However, is one of the organism of high concern in these food products as these organisms can tolerate the water activity as low as 0.83 to 0.86 under aerobic conditions and a favorable pH. In addition some other organisms like S. faecalis, Lactobacillus spp., Aspergillus, Penicillium and others could also be a cause of concern when the water activity of the food product is deviated. The table (s) 1 and 2 below illustrates some of the microorganisms and range of their water activity.

Table 1 Water activity and growth of microorganisms

Source: Maria S Tapia et, al., 2007 Table 2 Water activity and growth/ toxin production by moulds

Source: Maria S Tapia et, al., 2007

In addition to using sugars and salt to control water activity, some chemical preservatives including sulfites, sorbic acid, citric acid, benzoic acid, propionic acid, phosphoric acid and ascorbic acids are widely used in the preparation of IMF’s (Welti- Chanes et al., 1997). Also, propylene glycol, a humectant with specific antimicrobial activity and sorbates & propionates as mould inhibitors, are used for the stabilization of these products. These additives can be used in combination as and when required as per the pH and water activity of the final product.

Some kind of deteriorative chemical reactions i.e., non-enzymatic browning and lipid oxidation, dramatically increase in IMF’s. These biochemical changes are especially due to the presence of reducing sugars and amino groups in the food products. Inclusion of peels may trigger lipid oxidation which can be easily avoided or controlled with Good Manufacturing Practices and/ or by avoiding heat treatment. The reaction of sugar with amino group, also called as Maillard reaction, develops brown pigments and sometimes it is a desirable change in some of the food products. However, to completely avoid the undesirable browning of the food products, use or involvement of pentose sugars viz., ribose, xylose and arabinose should be avoided.

As far as products from fruits are concerned, action of enzymes cannot be completely avoided. The browning reaction initiated by Poly Phenol Oxidase (PPO) is not a new problem in fruit products. It is a faster reaction and causes sensory unacceptability and nutritional losses in fruit based products. As these are heat sensitive enzymes and IMF involves avoiding use of heat treatment, an exposure of food products to 70-90OC for short durations will control the enzyme activity.

FSSAI recommendations for IMF

The regulations called as ‘ and Standards (Food Products Standards and Food Additives) Regulations, 2011’ suggests general and specific standards for various categories of food products. The regulations defines the Intermediate Moisture Foods in its own way, as;

1. Murabba or Preserve: means the product prepared from suitable , sound whole or cut, grated fruits, rhizome or vegetables, appropriately prepared, suitable for the purpose, singly or in combination, by impregnating it, with nutritive sweetners to a concentration adequate to preserve it. It should have TSS- 65 per cent and fruit content not less than 55 per cent.

2. a) Candied fruits/ vegetables/ rhizome/ fruit peel means the product prepared from sound ripe fruits, vegetables, rhizomes or fruit peel, of any suitable variety, appropriately prepared by impregnating it with nutritive sweeteners to a concentration adequate to preserve it.

b) Crystallised fruits/ vegetables/ rhizome/ fruit peel means the product prepared from candied product by coating with pure crystallized sugar or by drying the syrup on wet candied fruit.

c) Glazed fruits/ vegetables/ rhizome/ fruit peel means the product prepared from candied product by coating it with a thin transparent layer of heavy syrup with or without pectin which has dried to a more or less firm texture on the product.

All these three types of products should have not less than 70 per cent total sugar of which 25 per cent should be of reducing sugar to total sugar.

3. The regulation defines Jam, jellies and marmalade extensively and suggests that these products should be prepared from any fruit ingredient singly or in combination. The fruit content in these products not to be less than 45 per cent, except from the fruits of strawberry, raspberry and ginger, where the fruit content should be 25 per cent, 23 per cent in cashew apples and 8 per cent in passion fruit, by weight. TSS should be 65 per cent for jams and 60 per cent for jellies and marmalades. Some other substances that may be added to these products are cane sugar, sucrose, dextrose and invert sugar, liquid glucose, honey, salt, herbs, spices, condiments and their extracts and other ingredients appropriate to the product whose standards are prescribed in the regulations. Pectin extracted from other fruits may be added at GMP level. As per the regulations the jam, jelly and marmalade should have original colour and flavor, consistency should be free from objectionable materials, defects and fermentation etc.

4. Dehydrated fruits: is the product prepared from edible part of suitable variety of sound fruit, free from blemishes, insect or fungal infections, of appropriate maturity, from which, moisture has been removed, under controlled conditions of temperature, humidity and air flow, to the extent that the product is preserved. The product shall have moisture content not more than 20 per cent.

5. Dehydrated vegetables: is the product, prepared from edible portions of suitable variety of sound vegetables, free from insect or fungal infection, free from blemishes, suitably prepared, from which moisture has been removed under controlled conditions of temperature, humidity and air flow, to the extent that the product is preserved. The final product should have uniform colour and shall be free from discolouration due to scorching or enzymatic reactions. The regulations give specifications for the following parameters in dehydrated vegetables:

S.No. Name of Moisture SO2 not Total ash Ash Peroxidase vegetable not more more not more insoluble test than (%) than than (%) dil HCl not (ppm) more than (%) 1 Green leafy 7 2000 Negative veg. 2a Tubers like arvi 7 2000 Negative b Lotus root 6 2000 Negative tapioca c Yam 6 2000 Negative D Carrot 6 2000 Negative E Potato 6 2000 Negative 3 Karela 6 2000 Negative 4 Cabbage 6 2000 Negative 5 Okra 8 2000 Negative 6 Other 8 2000 5 0.5 Negative vegetables 7 Powders of 5 2000 5 0.5 Negative onion & garlic 8 Powders of 5 2000 5 0.5 Negative other veg. including tomatoes

6. Raisins means the product obtained by drying sound, clean grapes of proper maturity belonging to Vitis vinifera L.,. The product may be washed, with or without seeds and stems and may be bleached with sulphur di oxide. The product shall be free from foreign matter, living insects, mould, dead insects, insect fragments and rodent contamination. The product shall have uniform colour, pleasant taste and flavor, free from odour and taste and evidence of fermentation. The product shall be free from added colouring matter. The product shall conform to the following:

1 Moisture (m/m) Not more than 15.0 per cent 2 Damaged raisins (m/m) Not more than 2.0 per cent 3 Sugared raisins (m/m) Not more than 15.0 per cent

7. Dates means the product obtained by drying sound, clean fruits of proper maturity belonging to Phoenix dactylifera. The product may be washed, pitted or unpitted, with or without cap, pressed or loose. The product may be treated with sugar, glucose syrup. Flour and vegetable oil. The product shall be free from foreign matter, living insects, mould, dead insects, insect fragments and rodent contamination. The product shall have pleasant taste and smell, free from odour and evidence of fermentation. The product shall be free from added colouring matter. The product shall conform to the following:

1 Moisture (m/m) Not more than 30.0 per cent 2 Ash insoluble in dil HCl Not more than 0.1 per cent 3 Blemished/ damaged Not more than 5.0 per cent units 4 Extraneous matter Not more than 1.0 per cent 8. Seedless tamarind ;

a) Tamarind (without seed) shall be obtained from Tamarindus indica L., after removal of outer covering and seeds from mature and ripe fruits.

b) It shall be clean and will not contain deleterious substances, obnoxious odour, external moisture and inorganic extraneous matter.

c) It shall be free from insect infestation, live or dead insects, mould growth, rodent hair and excreta, added colouring matter and impurities of animal origin.

d) It shall also conform to the following standards;

1 Moisture content Not more than 20.0 per cent 2 Organic extraneous matter Not more than 5.0 per cent (w/w) 3 Total ash w/w (on dry Not more than 6.0 per cent basis) 4 Acid insoluble ash w/w Not more than 1.0 per cent (on dry basis) 5 Crude fibre w/w (on dry Not more than 9.0 per cent basis) 6 Tamarind seeds Not more than 0.5 per cent 9. Dried Apricots means products prepared from sound, ripe fruit of varieties of Armeniaca vulgaria lam. (Prunus armenica L.) and processed by sun drying or by other methods of dehydration. The product shall have colour characteristics of the variety and the type of treatment and shall have flavor and odour characteristic of the product. The product shall be free from living insects or mites and reasonably free from extraneous vegetable matter, insect debris and other objectionable matter. The product can be whole (unpitted), whole (pitted), halves and/ or slabs consisting of portions of sound, ripe apricots of characteristic colour, irregular in shape, size and thickness and excluding whole fruit. The product shall conform to the following standards:

S.No. Characteristics Requirement 1 Moisture content % w/w (max) a Dried apricots not treated with any 20 preservatives B Dried apricots treated with 25 permitted preservatives 2. Defects Slabs % (w/w) maximum 10.0 Total shall Damaged fruits % (w/w) Maximum 10.0 not be more Broken fruits % (w/w) maximum 10.0 than 15.0 Insect damaged and dirty fruits % 5.0 per cent (w/w) maximum w/w Mouldy fruit % (w/w) maximum 1.0 Immature fruits % (w/w) maximum 10.0 10. Date paste, means product prepared from fruits of date plam (Pheonix) that are sound, consistent in colour and texture, harvested at the stage of maturity, washed, pitted and capped. Dates used for making date paste shall be free from diseases and contain no parthenocarpic or unripe fruits. They shall be free from fermentation and mould, insects fragments, eggs, larvae, dirt and foreign matter. Date paste shall be soft and have no alteration in smell and flavor. It shall not contain whole or broken pits, stalks or extraneous matter. The product shall be from single variety of dates or a blend of several varieties of dates. No ADDITIVES are allowed in this paste. It shall conform to the following standards:

1 Moisture % by weight Not more than 20.0 per cent 2 Total Ash % by weight Not more than 1.2 per cent 3 Acid insoluble ash % by Not more than 0.1 per cent weight

11.Honey; shall be the natural sweet substance produced by honey bees from the nectar of blossoms or from secretions of plants, which honey bees collect, transform and store in honey combs for ripening. It shall possess pleasant aroma, sweet flavor and taste characteristic of honey. Honey shall be free from organic and inorganic matter including visible mould, insects and insect debris, fragments of bees, brood, pieces of bees wax, grains of sand, and any other extraneous matter. Honey consists essentially of other sugars, predominantly fructose and glucose as well as other substances such as organic acids, enzymes and solid particles derived from honey collection. The colour of honey varies from nearly colourless to dark brown. The consistency can be fluid, viscous or partly to entirely crystallized. Honey sold as such shall not have added to it any food ingredients, including food additives, nor shall any other addition be made other than honey. Honey shall comply with the following requirements:

S.No Parameters Limits . 1 Specific gravity at 27OC, Min. 1.35 2 Moisture per cent by mass Max. 20 3 Total reducing sugars, per cent, by mass Min. 65 Carvia callosa and Honeydew honey, per cent, by mass, Min. 45 4 Sucrose, per cent, by mass, Max 5 Carvia callosa and Honeydew honey, Max. 10 5 Fructose to Glucose ratio (F/G Ratio) 0.95- 1.50 6 Total ash per cent, by mass, Max 0.50 7 a) Acidity 0.20 expressed as formic acid per cent, by mass, Max. b) Free acidity 50.0 milli equivalents acid/ 1000 g, Max 8 Hydroxy Methyl Furfural (HMF) mg/kg, Max 80.0 9 Diastase activity, Schade units, Min. 3 10 Water insoluble matters per cent, by mass, Max 0.10 11 C4 sugar, per cent, by mass, Max. 7.0 12 Pollen count/ g, Min 25000 13 Specific marker for rice syrup (SMR) Negativ e 14 Trace marker for Rice syrup (TMR) Negativ e 15 Foreign oligosaccharides per cent, Max. 0.1 16 Proline, mg/kg, Min 180 17 Electrical conductivity 0.8 mS/ a) Honeys not cm listed under Honey dew, Max. b) Honeys listed 0.8 mS/ under Honeydew, Min. cm 18 a) ∆ δ 13C Max +2.1 (Maximum difference between all measured δ 13C values); per mil b) ∆ δ 13C Fru-Glu +1.0 (The difference in 13C/12C ratio between fructose and glucose); per mil. c) ∆ δ 13C (per >-1.0 cent) Protein- Honey (The difference in 13C/12C ratio between honey and its associated protein extract); per mil.

Honey shall not be heated or processed to such an extent that its essential composition is changed and / or its quality is impaired. The product can be labeled according to floral or plant source, if it comes from any particular source, and has the organoleptic, physicochemical and microscopic properties corresponding with that origin: in the case of ‘Monofloral honey’ the minimum pollen content of the plant species concerned shall not be less than 45 per cent of total pollen content and in case of ‘ multi-floral honey’, the pollen content of any of the plant species shall not exceed 45 per cent of the total pollen content. ‘Honey dew honey’ comes mainly from excretions of plant sucking insects of order Hemiptera on the living parts of plants or secretions of living parts of plants.

In addition to the above mentioned details of the food product(s), also referred to as Intermediate Moisture Foods, these products should follow the GMP’s, additives as per mitted in Appendix-A of the regulations and Microbiological standards as in Appendix-B of FSSAI regulations.

References:

Cemeroglu,B. 1986. Fruit and Vegetable Processing Technology. Ankara.

Erickson, L.E. 1982. Recent developments in intermediate Moisture Foods. Journal of Food Protection. 45(5): 484-491.

Manorma Negi. Intermediate Moisture Foods. www.slideshare.net/manormanayokchey/ppt-of-f-n-veg-tech www.moisturecontrol.weebly.com/intermediate-moisture-food-imf.html www.core.ac.uk>download>pdf www.fao.org/3/y4358e06.html www.fda.gov/wateractivity www.gov.mb.ca/agriculture/foodsfatey

Elisavita Sandulachi. 2012. Water activity concept and its role in food preservation. In:researchgate.net/publication

Maria S Tapia, Stella M Alzamora and Jorge Chirife. 2007. Effects of water activity on microbial stability: As a hurdle in food preservation. In Water activity in Foods: Fundamentals and applications. Eds; Book Editor(s): Gustavo V Barbosa-Canovas, Anthony J.Fontana Jr., Shelly J. Schmidt and Theodore P. Labuza. Wiley Press.