The advantages include easy production, improved keeping quality, better digestibility and nutritive value, and therapeutic potential. Only the acid-tolerant bacteria can grow during milk fermentation.
(a) Egyptian Kishk is a fermented milk-wheat mixture that is stored as dried balls. To prepare kishk, wheat grains are softened by boiling, air-dried, and then ground. Milk is added to the ground wheat to produce a paste that is rolled into balls. Spices may be added to the balls before they are dried in the sun. The numbers of molds, yeasts, and bacteria have been examined. Penicillium and Mucor molds are found up to 103 g21. Yeasts are found in 104-106 g21 concentration but bacteria make up the highest numbers, which also contribute to the aroma with Lactobacilli found in 108g21 (Mahmoud 1977); (b) Russian Kefir is an acidic, mildly alcoholic milk made from cow, goat, or sheep milk that is able to keep longer. The predominant yeasts involved in fermentation include T. holmii and S. delbrueckii although Candida kefir and S. cerevisiae are the yeasts that are commonly isolated (Marshall 1984). During the preparation of kefir, Kefir grains are added to pasteurized milk and incubated at 18-25°C for 1-2 days. The mixture contains Kefir grains, which consist of yeasts and lactic acid bacteria held together with the help of a polysaccharide gum and these are removed by sieving; (c) Russian Koumiss: This is produced from ass milk, camel milk, or mare milk. Lactic acid bacteria and the lactose fermenting yeasts Torula kumiss and Saccharomyces lactis cause fermentation (Kosikowski 1982). Fresh milk is first heated at about 90°C for 5 min and cooled before inoculation of starter and incubation at 28°C. The incubate is agitated every 24 h and then cooled to form koumiss. Koumiss has both nutritive and therapeutic values and has been reported to be effective in the treatment of pulmonary tuberculosis in Russia; (d) Lebanese Labneh: This is formed from goat or sheep milk. Lactose-fermenting yeasts and lactic acid bacteria cause fermentation; (e) Cheese: Cheese-making comprises several steps: preparation of milk; addition of starter and ripening (souring), renneting and coagulation, and ripening/ curing of cheese curd into the final product. Molds such as Penicillium roqueforti, P. glauceum, P. camenberti, Geo-trichum candidum, and Mucor racemosus are used in ripening. Different combinations of molds and bacteria are used for different varieties of cheese; (f) Indian Dahi: Dahi is produced by lactic fermentation of milk as a bioproduct of alcoholic fermentation by yeast. Raw milk is boiled for a period of a few seconds up to 10 min, then cooled before addition of starter and incubation at room temperature for 8-16h (Baisya and Bose 1975).
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