The Effect of Different Heat Treatment on the Nutritional Value of Milk and Milk Products and Shelf-Life of Milk Products. A Review

This Review is concern on the effect of different heat treatment on the Nutritional Value of milk and milk Products and shelf-life of milk products. Milk and its derivatives are proposed as being useful foods throughout all life periods, in particular during childhood and adolescence, when their contents of calcium, protein, phosphorus, and other micronutrients might promote skeletal, muscular, and neurologic development. Temperature is the necessary environmental factor for the growth of microorganism. Heat treatment is the most widely used processing technology in the dairy industry. milk is treated at high temperature (85 C for 2-3s) in a short-time, flash process (72-75 C/15-30 s) in plate heaters; or by the low temperature or holder process, in which it is heated at 63-66 C for at least 30-32 min, with stirring, and is then cooled. The fat, fat-soluble vitamins, carbohydrates and mineral' of milk are essentially unaffected by heal treatment. Proteins and water-soluble vitamins are the components which are mainly affected by the heat treatment. Pasteurization temperature, ranged from 72 to 94 C/15s had no effect on the microbiological and sensory shelf-life of aseptically packaged milk into plastic bottle, which lasted 11 d under storage at 9 C. During industrial yogurt manufacture, the mixes are generally heated at 90 or 95 C for 3-7min before cooling down to fermentation temperature. It is well established that heat treatment implemented during yogurt manufacture affects the acidification rate and incubation time. The shelf life of "fresh" yogurt may be only a couple of weeks for unprotected operations and up to 6 weeks or more for well-operated, ultraclean operations. Cheese is the ripened or unripened soft, semi-hard, hard, or extra-hard product, which may be coated, and in which the whey protein/casein ratio does not exceed that of milk, obtained by coagulating wholly or partly the protein of milk, skimmed milk, partly skimmed milk, cream, whey cream or buttermilk, or any combination of these materials. The heating treatments and holding time significantly influenced yield, TS and protein recovery of cow milk Ricotta cheese. Heat treatment of milk (72 C, no hold) meant for Mozzarella cheese making improved protein and Total Solids (TS) recovery but decreased the fat recovery, gave soft-bodied cheese, improved flavor score and keeping quality and ensured public health safety. Generally, unprocessed milk held at high ambient temperatures has a shelf-life from 2-3 hours up to 24 hours. Cheese, however, has a shelf-life from 4-5 days up to five years depending on the variety. Churning at low temperature (TL) and TLW results in butter with an average water droplet size at day 5 of 5.5mm, while commercial butter had an average diameter of 2.8 mm.