Milk is a treasure house of about 2000 ingredients. Value addition to milk products would provide health benefits to the consumers, improve the scale of the economy in the dairy industry. Indian dairy industry must seize the opportunity and gainfully exploit the highly dynamic, exciting, and promising future in the field of value added milk products, write, M.K. Sanyal, S.K. Gangopadhyay, and S.C. Paul.
Value addition to milk products is an age-old practice in India. Most of our traditional milk products such as sandesh, payasam, burfi, dahi, rasogolla, srikhand, kulfi etc. are value added milk products. Many of the value added functional dairy foods are designed to decrease the chances of diseases, managing the disease conditions and promoting the health of the consumers. Some Western countries are already marketing a variety of such foods incorporated with specific health-promoting factors and food ingredients derived from fractionation of milk employing emerging technologies like ultrafiltration, diafiltration, microfiltration, nanofiltration, reverse osmosis, fat fractionation, electrodialysis, etc.
Enrichment with Milk Fractions
Milk products incorporated with specific milk fractions – commonly known as functional dairy foods – provide nutrition as well as health benefits. They are also termed as nutraceuticals, health foods, medical foods, pharma foods, refreshing foods, bio foods, designer foods, performance foods, mood-elevating foods, supplements etc.
Milk proteins prove to be better than plant proteins in terms of quality and absorption characteristics in human beings. Whey proteins possess anti-cancer, anti-hypercholesteromic, immuno-modulatory, gelling, foaming, emulsifying and flavour development properties, to mention a few and can be used in foods for sportspersons, elderly people or HIV patients apart from common foods (Singh, 2003). Immunoglobulins (Ig) present in whey enhance immune response and can help in preventing tumour formation. (Ig) molecules can pass through the placental barrier in mothers to provide passive immunity to the newborn which, however, is not the case in bovines (Bhatia, 1997). Lactoferrin (Lf) – an iron-binding glycoprotein – inhibits microbial growth by depriving the organisms of iron.
Lysozyme (Lz) destroys bacterial cell wall and chitin cell wall components of most fungi. It also stimulates the growth of probiotic bifidobacteria by supplying -NAG-NAM, a bacterial cell wall hydrolysate component, a lactalbumin – a calcium-binding protein – enhances calcium absorption (Chandan, 2000). Lactoperoxidase (LP) catalyzes the enzymic oxidation of thiocyanate molecules by H2O2 thereby producing short-lived intermediary compounds possessing antibacterial properties, which either kill or inhibit bacteria and prolong the shelf life of raw milk at ambient temperature.
Colostrum is richer in many functional components like Lf, LP, Lz, lg, cytokines, growth factors etc. than milk and is being increasingly used to improve the functional properties of dairy foods. Casein helps in transporting minerals like calcium and phosphorus.
Milk fat provides high energy, prevents emaciation due to protein-sparing action, protects organs, insulates the body from external onslaughts, carries fat-soluble vitamins and essential fatty acids like to w 3-linoleic, linolenic, arachidonic, eicosopentanoic and docosahexanoic acid. It also influences the sensory properties of foods. Conjugated linoleic acid is antioxidant and may play a role in the prevention of breast cancer and colon cancer, reduction in chronic inflammation, increase in bone density and normalization of blood glucose level (Chandan, 2000). Fatty acids present in milk fat do not increase the serum cholesterol level but lower the surface tension and provide barrier to pathogens apart from decreasing pH to help protein digestion.
Lactose enhances absorption of calcium and magnesium, stimulates bifidobacteria in the colon, is less cariogenic and suitable for patients suffering from diabetes. Lactulose, an isomer of lactose, is produced from a lactose hydrate in heated milk and acts as a prebiotic to bifidobacteria as lactulose is not hydrolyzed in the small intestine. Hydrogenation of glucose moiety in lactose produces lactitol – a polyol comprising galactose and sorbitol – which is permitted by EEC for use in foods for diabetics, low calorie slimming foods, low-calorie tabletop sweeteners, bakery products for crispiness and in products that are safe to teeth.
Minerals such as calcium, phosphorus and magnesium help in bone growth and maintenance. Calcium regulates blood pressure and prevents osteoporosis. Several rat and water-soluble vitamins present in milk can be used to fortify value added milk products.
Physiologically significant bioactive peptides formed during the preparation of fermented milk products and also during the passage of milk proteins through human digestive system have an extra-nutritional role in the intestine and circulatory system. Some milk protein hydrolysates prevent formation of Angiotensin II from Angiotensin I, thereby reducing the chances of an increase in blood pressure. Immunopeptides, phosphopeptides, casokinins and casoplatelins perform the job of improving immune properties, transporting minerals, reducing blood pressure and diminishing blood-clotting tendencies, respectively. Opoid (possesses analgesic properties) agonist like casomorphins and lactophorins, and opoid antagonist such as lactoferroxins and casooxins have been isolated from milk proteins (Chandan, 2000).
Use of Probiotics
Probiotics refer to the viable mono or mixed cultures of microorganisms, which on ingestion in certain doses exert beneficial health effects to the host by improving the properties of indigenous microflora in the gastro-intestinal (GI) tract. Probiotics are mostly selected from lactic acid bacteria (LAB) group in which lactobacillus species normally predominate because of their capacity to grow rapidly and tolerate acid environment. Probiotics bring about changes in enteric flora with decrease in E.coli count, colony formation on the intestinal wall thereby preventing colonization by pathogenic microorganisms, synthesis of lactate with consequent decrease in intestinal pH, neutralization of toxic amines and ammonia, generation of antibacterial substances, immunomodulation, competition with other microorganisms for nutrients in the GI tract etc. (Chandan, 2000).
Probiotics put up ecological barriers to the infective bacteria. Production of H2O2 and bacteriocins by these organisms prevents proliferation of pathogens. They can prevent diarrhoea. Probiotics exhibit antimutagenic and anticarcinogenic activity, inhibit cholesterol synthesis by the body, stimulate the immune system against certain antigens and pathogens, reduce lactose intolerance by metabolizing lactose, improve calcium absorption, synthesize vitamins and help in predigestion of proteins (Mishra and Prasad, 2000).
LAB are extensively used in foods because of their role as preservatives, nutritive and therapeutic agents. They enhance longevity of humans and are natural inhabitants of GI tract. Probiotics for application in value added dairy foods may include lactobacilli such as L. acidophilus, L. plantarum, L. casei subsp. rhamnosus GG, L. brevis, L. delbruckii subsp. bulgaricus etc.; bifidobacteria such as B. bifidum, B. infantis, B. longum, B. animal is, B. breve etc.; yeast such as Candida kefir, Kluveromyces fragilis, Saccharomyces boulardii or others like Enterococcus faecium, Lactococcm lactis subsp. lactis, Lactococcus lactis subsp. cremoris etc (Ram and Bhavadasan, 2002).
Enriching Milk Products with Plant Products
Extenders from cheap vegetable sources may be used in dairy products for value addition to milk products. Addition of potato/ sweet potato starch in the preparation of Gulab Jamun; soya- or groundnut proteins in chhana, paneer or Gulab Jamun; and refined vegetable oil in ice-cream to replace milk fat not only reduces the cost of the products but also saves valuable milk solids for alternate uses. Incorporation of viscous polysaccharides into dairy foods may reduce low-density lipoproteins and total serum cholesterol in blood (Chandan, 2000).
Extracts from herbs like tulsi, dandakalash, mint, brahmmi etc.; fruits such as mango, grapes, pineapple, nuts etc. and vegetables such as carrot, beans etc. are being also used in certain Indian dairy products to aid in health management.
Addition of Additives to Milk Products
The use of additives in small quantities during production, processing, packaging and storage of dairy products may bring about certain desirable changes. For example, emulsifiers and thickeners provide physical form and texture; preservatives and antioxidants prolong shelf life; vitamins, minerals and nutrients contribute towards health; flavours, colours and sweeteners improve sensory quality etc. Food industry is currently using more than 3000 additives. Incorporation of carrageenan, algmate or sodium chloride into milk increases moisture retention beyond 60% in paneer, which is otherwise difficult to achieve with the existing technologies (Sanyal and Yadav, 2000).
Naturally occurring antimicrobial compounds (biopreservatives), tree-radical trapping agents, oxygen scavengers, chelating agents etc. can play vital role in the production of value added dairy products. Biopreservatives may be of microbial, plant or animal origin. They help in extending shelf life and safety of foods. Biopreservatives produced by lactic acid bacteria such as nisin, pediocin, leucocin, sakacin, plantaricin, helveticin etc. are getting serious attention from researchers for biopreservation of foods (Malik, 2000).
Modification in Processing Conditions
Manufacturing technique of dairy products may be modified to regulate the state and proportions of the major constituents – water, fat and protein. Lowering of coagulation temperature of milk increases the retention of moisture in coagulated dairy products.
High hydrostatic pressure (100-600 MPa) to food products improves the keeping quality without causing damage to the heat labile components.
Utilization of Recombinant Dairy Enzymes
Recombinant chymosin obtained through cloning and expressing calf rennet genes in E. coli works satisfactorily during the production of cheese and overcomes problems related to the development of bitter flavour due to improper proteolysis as is often the case with microbial rennet (Batish et al., 1998). Research works on recombinant dairy enzymes for use in the manufacture of cheese from buffalo milk needs to be given priority as the use of calf rennet is banned in India.
Texturization of Milk proteins
Texturized soy protein is widely used as meat extender, replacer or analogue. Texturization of proteins is generally accomplished by extrusion process, which stretches, and shears the protein into new fibre-bundle like structure that is able to withstand hydration, cooking and other procedures adopted in the preparation of foods (Onwulata et al. 2003). Works are being carried out to texturize whey proteins from whey protein concentrates, whey protein isolates and whey albumins by extrusion process for use in snack foods, as meat extender/analogue, instant thickeners to replace starch and other hydrocolloids, thermo coagulated gels, edible food wraps etc.
Extruded products containing 65-80% starch, 20-35% whey proteins and 10-15% moisture have been prepared for use in puffed snacks or as meat extenders (Onwulata et al. 2001). Beef patties extended with texturized whey proteins and cornstarch up to 40% level were acceptable to consumers (Hale et al., 2002). Coextrusion with whey proteins, however, poses problems such as collapsing of whey proteins in the starch matrix, increase in hardness, reduction in expansion properties in snacks etc. High temperatures used in extrusion process may also cause Maillard reaction, discolouration or denaturation of proteins. However, incorporation of texturized whey proteins into foods would improve nutritional quality, provide scope to reduce calorie from carbohydrates in a food and help in utilizing whey proteins in value added milk products.
Intelligent Packaging for value addition to milk products
Incorporation of active substances into the packaging materials may permit the latter to perform functions such as antimicrobial activity, ethanol emission, scavenging of oxygen/moisture/ethylene etc. apart from providing the usual barrier and protective properties. Such active packaging technologies (APT) are designed to add value to the food products through enhancement of shelf life without adversely affecting their quality and safety. Among various APT, the oxygen scavenging system and antimicrobial system hold greatest promise. The former absorbs oxygen gas within the package thereby limiting the growth of aerobic microorganisms including molds and retarding oxidation of fat. The latter controls microbial contamination by extending the lag phase of specific organisms, decreasing the growth rate and total population of the microorganisms.
Antimicrobial substances, gas emission or flushing, radiation etc. can exert antimicrobial effects. The antimicrobial chemicals generally occupy the amorphous structural regions in the polymeric structure of the packaging materials without affecting mechanical strength and machinability (Han, 2000). Modified atmospheric packaging wherein the air inside the package is replaced by a suitable mixture of gases enhances the shelf life of the food products considerably (Rajorhia, 1998).
Packaging of processed American cheese with high-density polyethylene films containing 10% potassium sorbate and subsequent storage at room temperature allowed the cheese to remain microbe-free for 5 months (Han, 2000). Sorbic acid and its potassium salts to a wax layer extend shelf life of natural cheese while a shrink-wrapping film of imazalil – an antimycotic agent – in low-density polyethylene (Weng and Hotchkiss, 1992) and an imazalil-bound ionomer film (Halek and Garg, 1989) help to control contamination in cheese due to antifungal properties. Use of coatings and films made of edible substances such as whey proteins, corn zein, polylactic acid etc. treated with edible antimicrobial agents (nisin, lysozyme, lactoferrin) and plasiticizer (glycerine, sorbitol) for food packaging can play a key role.
Improvement in Sensory Quality
Milk fat has a capacity to dissolve flavour compounds and release them slowly when the product is eaten, thereby contributing towards perception of flavour. With major reduction in fat content, the sensory quality of the product – the most important selling point – gets affected adversely. Use of fat replacers offers scope to the consumers to take the reduced or low fat formulations of the desired foods without compromising much on the basic food patterns. Fat replacers may help replace the mouthfeel of fat but do not act as fat substitutes on weight basis.
Fat replacers could be protein-based such as whey protein concentrates and microencapsulated proteins; carbohydrate-based such as starches, maltodextrins, dextrins, polydextrose, cellulose gel, gums etc. or fat-based like emulsifiers, structured lipids, acaloric synthetic compounds etc. (Sachdeva, 2000) These substances may find use in different kinds of cheese, cultured dairy products, spreads, frozen desserts, modified butter etc. Several commercial formulations of fat replacers such as Simplesse 100, Calpro 75, CMP-1, AMP 800, Slendid, Ex-Cel etc. are available in the market.
Limited lipolysis of milk lipids in raw milk produces free fatty acids, which aid in the development of flavour in milk and milk products. Use of enzyme preparations such as Accelase and Naturage enhances the sensory characteristics of low-fat Gouda cheese.
Value Added Functional Milk Products
Value added functional dairy foods may be developed as per the requirements of different segments of population
- Low lactose formula for infants and lactose-intolerant people
- Geriatric foods with the properties to prevent bone degeneration, constipation and indigestion for elderly people
- Protein-enriched formulated dairy products for growing children and those suffering from protein malnutrition
- Sports drinks or foods designed to reduce sweating, fatigue etc. and provide instant energy to sportspersons
- Formulations containing specific vitamins, minerals, calorie etc. for expecting or lactating mothers
- Low or reduced-fat formulated dairy products containing fat replacers for those suffering from coronary heart diseases and those vulnerable to heart-related problems.
Dairy farmers in some of the western countries get a high subsidy. If such subsidies are extended to Indian farmers or as per WTO stipulation the subsidy to western farmers is reduced to 100% than India’s milk products can become more competitive in the international market. Further, India produces milk at less cost because of cheap labour and unique integration of animal husbandry practices with traditional agriculture. However, it would be difficult to export our innovative value added milk products unless we improve the quality of milk, particularly in view of the WTO’s Agreement on Sanitary and Phytosanitary measures covering the application of food safety, animal and plant life and health.
The Indian middle-class population with more purchasing capacity is increasing. There is also a clear shift visible in the lifestyle and food habits among people world over which could increase the consumption of value added processed foods. At present, India is mostly exporting skim milk powder, whole milk powder, ghee and butter. Since the era of milk scarcity is over, Indian dairy industry must utilize the opportunity to gainfully exploit the market of value added milk products – both western and traditional Indian milk products – in the /milk deficit countries in Asia and Africa to begin with and extending the market thereafter to other areas. Packaging materials along with suitable equipment and technologies should be developed for packaging the value added milk products.
The need for building strong brands of Indian milk products in the global market is long overdue. This is particularly important in context to the exportable surplus milk in India, free investment climate in foreign countries and availability of sophisticated tools for communication. Effective advertisement on mass media like television, newspapers etc. particularly in the western countries, emphasizing the quality aspects of buffalo milk and its products is needed to counter the adverse propaganda of a section of foreign people. Printing details of compositional and nutritional facts on packages would be helpful. The fact that buffalo milk is best suited for mozzarella cheese should also be stressed upon.
Milk is a treasure house of about 2000 ingredients, many of which possess excellent functional and nutritional properties and can be used to develop value added milk products. Value addition milk products would provide health benefits to the consumers, improve the scale of economy in the dairy industry, help pay remunerative prices to the dairy farmers and earn foreign exchange for the country if designed, processed and marketed judiciously following scientific principles. Buffalo milk offers many competitive advantages over cow milk and should, therefore, be the first choice for value added foods. There is great potential for traditional Indian milk products for innovation and value addition. Education on value addition to milk products must be made more relevant to the future needs. Indian dairy industry must seize the opportunity and gainfully exploit the highly dynamic, exciting and promising future in the field of value added milk products.
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