Describe the following in about 150 words each: (a) Quarantine as a measure to prevent the spread of animal disease (10…

(a) Quarantine as a measure to prevent the spread of animal disease

Quarantine is the isolation of animals that are sick, suspect or newly arrived, for the period needed to confirm that they are free of communicable disease. Imported livestock are quarantined under the Livestock Importation Act, 1898 (amended 2001), at Animal Quarantine and Certification Service stations, and the period and tests depend on the species and on the diseases of concern. On a farm, new or returning animals are kept apart for 3–4 weeks, observed daily, tested and vaccinated. Key points are a location away from the herd, separate staff, feed, water and equipment, disinfection, disposal of waste, and movement restriction. Animals are released after negative tests and the completion of the period, and diseased animals are treated or slaughtered according to the disease. Quarantine keeps out exotic and transboundary diseases such as foot-and-mouth disease and peste des petits ruminants, and protects livestock trade.

(b) Preparation of flavoured and sterilized milk

Flavoured milk: milk is standardised (for example 3% fat and 8.5% SNF), pre-heated to 60–70°C, and sugar (about 6–8%), flavour (chocolate, vanilla, strawberry or cardamom), permitted colour and stabiliser are added. It is homogenised, pasteurised and cooled to below 5°C.

Sterilized milk: standardised milk is pre-heated and homogenised at about 60–70°C to prevent creaming. It is filled into clean glass bottles, sealed with crown corks, and sterilised in-bottle in a retort or autoclave at about 115–120°C for 15–20 minutes, destroying all microbes and spores. Flavoured sterilised milk is made by adding sugar, flavour and colour before filling. After sterilisation, the bottles are cooled gradually to avoid breakage. The product is commercially sterile and keeps for several months without refrigeration, but heating gives a slight cooked flavour and brown colour.

(c) Difference in physical quality and chemical composition of cow and buffalo khoa

Khoa is milk concentrated by heat to a semi-solid mass with about 25–30% moisture and a legal minimum of 30% milk fat on dry matter, used for sweets.

Physical quality: buffalo khoa is white, soft and smooth, with a greasy, compact body and mild cooked flavour; it spreads easily. Cow khoa is yellowish, harder, drier, and coarse or granular, with a sticky, crumbly body, and is more prone to browning.

Chemical composition: buffalo milk has higher fat, protein and total solids, so buffalo khoa has more fat and protein and less lactose per 100 g, with about 25–30% moisture; cow khoa has lower fat and more lactose and moisture, and more carotene gives its yellow colour. Buffalo milk gives a higher yield, about 20–22 kg per 100 litres against about 17–18 kg for cow milk.

Buffalo khoa is preferred for burfi, peda and gulab jamun because of its texture and yield.

(d) Value-added poultry meat products

Value-added products are made by further processing chicken meat to raise its value, variety and shelf life.

• Comminuted and emulsion products: sausages, frankfurters, nuggets and patties, made from chopped or emulsified meat with fat, salt, spices and binders.
• Restructured products: rolls, loaves and cutlets.
• Cured and smoked products: ham, bacon-type and smoked chicken.
• Ready-to-eat and ready-to-cook products: tandoori chicken, tikka, kebabs, curries, momos, samosas and canned meat.
• Others: chicken pickle, soup powder, meat balls, chicken spread and dehydrated products such as jerky.
• Egg products are separate.

They reduce wastage of spent hens and broilers, suit urban demand, and give better returns, if hygienically processed and kept cold.

(e) Physico-chemical changes in meat after slaughter

Pre-rigor: circulation stops and muscle keeps respiring anaerobically, so glycogen is changed to lactic acid by glycolysis and pH falls from about 7.0 to 5.4–5.6, while ATP and creatine phosphate are used up. Fast glycolysis in warm carcasses gives pale, soft, exudative (PSE) meat, and low glycogen, as in stressed animals, gives dark, firm, dry (DFD) meat.

Rigor mortis: when ATP is exhausted, actin and myosin combine permanently, muscles shorten and stiffen, water-holding capacity is lowest near the isoelectric point, and the meat is tough. Rigor sets in within a few hours and lasts about 24–48 hours (species and temperature dependent).

Post-rigor (ageing): muscle calpains and cathepsins break down the structural proteins, and the meat becomes tender, more juicy and more flavoursome.

Colour: purple deoxymyoglobin becomes bright red oxymyoglobin on exposure to air and brown metmyoglobin on oxidation.