Consumers need nutritious wholesome pure and safe food In recent

Consumers need nutritious, wholesome, pure and safe food. In recent years, consumers have placed increased emphasis on food safety, which include safety, purity, wholesomeness and value. Because milk contribute a very significant proportion in our daily diet. Milk considered to be closest to the nature's perfect food, is an excellent source of calcium, a good source of minerals and high-quality proteins, the only source of lactose and lipids, the most valuable component, which also forms the basis of milk pricing. India is largest milk producing country in the world, with 127 million tonnes of milk produced annually.

Milk is more prone to adulteration by addition of vegetable oil, starch, sugar and flour to adjust its composition illegally. Addition of urea, detergents and pond water in sour and spoiled milk is also in practice to make it fit for processing and consumption. This lead to deterioration of quality of milk and a risk to consumer's safety.

As milk is very perishable and deteriorate rapidly due to high moisture content, chemical preservatives are added to milk samples so that composition does not changes.

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Various studies have been conducted to report the effects of preservatives on composition of milk, but the studies describing preservatives and their limitations have not been previously described.

Chemical milk preservative has been practiced for a long time since milk fat testing become a routine exercise. Several substaces and formulations have been used in the past, but the search for ideal milk sample preservative continues. The type of preservatives depends upon the purpose for which it is required.

If the sample requires short-term preservative, for example, for carrying sample from the farm to the laboratory for analysis, a preservative providing small increase in shelf life will suffice. On the other hand, in situations where samples are collected from the market by food authorities and sent to a food laboratory for analysis and when disputes require the intervention of referral laboratory, a preservative providing longer shelf life is required.

Some organic preservatives such as formaldehyde, toluene or hydrogen peroxide have been described, the first chemiczk preservatives used in developed countries were potassium dichromate, mercuric chloride, boric acid or combinations of these. Some newer preservatives, such as bronopol or sodium azide have also been recommended. Most of these preservatives are bacterial in nature.

Coliform bacteria and staphylococci are more sensitive to the effect of sodium azide than mesophillic bacteria, enterococci and lactobacilli, whereas enterococci are more resistant to chloramphenicol than salmonella sp., Esherichia coli, Lysteria sp., and staphylococcus aureus. Research dealing with combinations of antibacterial agents and bacteriostatic such as chloramphenicol and nitrofurazone brought our new mixtures that were good enough to preserve milk for 3 days without affecting the instrumental analysis of milk by Milkoscan, Bactoscan and Fossomatic systems. One of these mixtures Azidol (containing chloramphenicol and sodium azide) was most commonly used in all milk testing laboratories in Spain.

A few attempts have been made to improve and maintain the shelf life of milk by using chitosan, which is a natural modified biopolymer derived by deacetylation of chitin a major component of shells of crustacean. Lee (2000b) studied the effects of water soluble chitosans with 3 different molecular weights (0.2 to 3, 3 to 10 and 10 to 30 KDa) on the physiochemical and sensory properties of milk. Consistency of chitosan added milk increased with increasing molecular weight and concentrations. Milk containing 0.5% and 1.0% chitosan could be sterilized at 730 for 15 minutes without protein coagulation. Addition of 0.5% water soluble chitosan to milk negatively affected the sensory quality of color, taste and flavor, browning in color and chemical off-flavor. However there is no differences in sensory quality between coffee flavored milk containing chitosan, this may be due to masking effects of coffee.

Ha and lee (2001) studied the effectiveness of water soluble chitosan (0.03%) to minimize the microbial (bacterial and yeast) spoilage of processed milk. Complete inhibition of microbial growth was observed in banana-flavored milk in contrast to that observed in control milk (without chitosan), during chitosan also control relatively high pH than that of control milk during storage.

Till now there is no way to increase the shelf life without having effects on color, appearance, taste, aroma of milk. So we take initiative through the knowledge of bioinformatics tools to increase the shelf life of milk, for that we select the Beta-2-microglubulin (B2M) gene of bos taurus cattle commonly called Zebu, which is found in hot climates and tropical parts of the world such as sub- saharan Africa, India, china and Southeast Asia. B2M gene help in presentation of peptide antigen to the immune system. It encode for serum protein found in MHC class 1heavy chain on surface of all nucleated cells. As it encode for antimicrobial protein displays antimicrobial activity in amniotic fluid. The Beta -2-microglubulin also called lactollin.

Chapter 2 Review of literature

2.1 Need to extend the shelf life

Consumers demands are increasing for high food quality and have expectations that the product quality will be maintained at high level during the time of purchase and utilization. The expectations are not only regarding the food quality should be safe, but also need to minimize unwanted changes in sensory quality. In the UK, the date coding to be used is checked by the total life of the product: for microbiologically highly perishable foods, a 'use by' date is needed, while for other foods, including foods with more than 18 months a 'shelf-life', a 'best before' or a 'best before end' date is needed.

McGinn et al., (1982) reported that microbiological changes are of primary importance for short-life products and chemical and sensory changes for medium- to long life products; all three types of changes can be necessary for perishable products.

The more recent IFST Guidelines (1993) provide a more workable explanation of shelf-life:

Shelf-life is explained as the period during which the food product will:

(i) remain safe;

(ii) retain desired sensory, phsyiochemical and microbiological characteristics;

(iii) comply with any label declaration of nutritional data,

when stored under the recommended conditions.

2.2 Factors influencing shelf life

Shelf life can be affected by various factors and categorized into intrinsic and extrinsic factors (IFST, 1993). The final properties of product are called intrinsic factors and include the following:-

· Water activity (aw) (available water).

· pH value and total acidity; type of acid.

· Available oxygen.

· Nutrients.

· Natural microflora and surviving microbiological counts.

· Natural biochemistry of the product formulation (enzymes, chemical reactants).

· Use of preservatives in product formulation (e.g. salt).

Extrinsic factors are those factors the final product encounters as it moves through the food chain. They include the following:

· Time-temperature profile during processing; pressure in the headspace.

· Temperature control during storage and distribution.

· Relative humidity (RH) during processing, storage and distribution.

· Exposure to light (UV and IR) during processing, storage and distribution.

· Environmental microbial counts during processing, storage and distribution.

· Composition of atmosphere within packaging.

· Subsequent heat treatment (e.g. reheating or cooking before consumption).

· Consumer handling.

The interaction of such intrinsic and extrinsic factors can inhibits or stimulates a number of processes which limit shelf-life. These processes can be conveniently classified as:

2.1.1 Microbial changes:- During storage period the growth microbes occur due to various reasons, i.e, microbes present starting of storage; the physicochemical properties of the food, like moisture content, pH, presence of preservatives; the method used in the production of the food; and the outer environment of the food; the surrounding gas composition and storage temperature. The growth of food-poisoning organisms such as Salmonella species will not be accompanied by changes in appearance, odor, flavor or texture that could be detected by the human senses and it cause serious health concerns.

2.1.2 Chemical deteriorative changes:- most of the food spoilage occur due to reaction within food or with outer component, for example oxygen. Rancidity is mainly occur in fat-containing foods and can occur through different mechanisms, for example oxidative reactions and flavor reversion reactions. Enzymatic reactions limit the shelf-life of fruits and vegetables, and oxidation reactions limit the shelf-life of meat. Chemical hydrolysis can occur in food containing intense sweeteners, reducing sweetness.

2.1.3 Physical deteriorative changes:- Moisture can be removed and added during processing of food or through surrounding migration of moisture, which is reason for physical deterioration. This is easily observed in dry products such as breakfast cereals and biscuits can lose their crispness through moisture uptake. Freezer burn is also a result of moisture migration from the surface of frozen foods. Other migration phenomena can limit shelf-life, such as migration of fat from one component to another and the bleeding of colors in composite products such as chilled desserts. Physical changes in packaging materials by chemical reaction can aslo limit the shelf life. Migration of chemical components from the packaging material due to change in permeability can produce taints and this can be particularly serious in products with a long shelf-life.

2.1.4 Temperature-related deteriorative changes:- Spoilage can occur at both high and low temperatures. The minimum required temperature for growth of pathogens and spoilage organisms define the importance of temperature control in preventing microbial spoilage. The rise in temperature can lead to chemical reaction, which could be a cause of spoilage. In foods containing fats, solid fat turn into liquid and act as a solvent for reactions to occur, e.g forming bloom in chocolate. High temperature can also change crystalline characterstics of food. Varying of temperature can be reason of ice crystal formation in frozen foods such as ice-cream. In disparity, high temperatures can reduce the of staling in bread, although the condition with other baked products can