掺假原料乳对酸牛奶发酵酸度和粘稠度的影响

用５种掺假原料乳和不掺假原料乳对酸牛奶成品粘稠度和酸度进行对比试验，结果表明：不掺假原料乳的密度为１０２８～１０３２，制成酸牛奶的酸度为１１０～１１５°Ｔ，２０℃时粘度为３５０ｍｐａ·ｓ。当原料乳密度由１０２３升至１０２８，酸牛奶酸度由５０°Ｔ升至１１０°Ｔ，粘稠度由１６２ｍｐａ·ｓ升至３５０ｍｐａ·ｓ逐渐趋于正常；原料乳的酸度从１５°Ｔ升至１８°Ｔ时，酸奶的酸度由７９°Ｔ升至１０４°Ｔ，粘度由２３６ｍｐａ·ｓ升至３５０ｍｐａ·ｓ，当原料乳的酸度升至２０°Ｔ时，酸奶的酸度偏高达１２１°Ｔ，而粘度下降到２９５ｍｐａ·ｓ，影响酸奶组织状态，有乳清析出；原料乳中掺入Ｎａ２ＣＯ３量由００５ｇ／１００ｍＬ增至０２ｇ／１００ｍＬ时，酸奶的酸度由９７°Ｔ降到４２°Ｔ，粘度由２８０ｍｐａ·ｓ降至２０８ｍｐａ·ｓ；原料乳中掺入ＮａＣｌ量由０２５ｇ／１００ｍＬ到１２５ｇ／１００ｍＬ，酸奶的酸度由１０１°Ｔ降至５２°Ｔ，粘度由２８２ｍｐａ·ｓ降至２０９ｍｐａ·ｓ；掺青霉素原料乳由０１Ｉ·Ｕ／ｍＬ增至０４Ｉ·Ｕ／ｍＬ时，酸奶酸度由１０５°Ｔ降至４７°Ｔ，粘度由２８６ｍｐａ·ｓ降至２１３ｍｐａ·ｓ。

Effect of Adulterated Raw Milk on the Acidity and Viscosity of Yoghurt

A comparison experiment was made between 5 kinds of the adulterated raw milk and the fresh one. The results showed that the acidity and viscosity of yoghurt produced with the normal raw milk with density of 1 028～1 032 were 110～115°T and 350 mpa·s (20℃), respectively. As increased the milk density from 1 023 to 1 028, the acidity and viscosity of yoghurt raised from 50 °T to 110°T and from 162 mpa·s to 350 mpa·s, respectively. As increased the milk acidity from 15°T to 18°T, the acidity and viscosity of yoghurt raised from 79°T to 104°T and from 236 mpa·s to 350 mpa·s, respectively. As increased the milk acidity to 20°T, the acidity of yoghurt raised to 121°T, however, the viscosity dereased to 295 mpa·s and whey appeared. As added Na 2CO 3 increased from 0 05 g/100mL to 0 2 g/100mL, the acidity and viscosity of yoghurt decreased from 97°T to 42°T and from 280 mpa·s to 208 mpa·s, respectively. As added NaCl increased from 0 25 g/100mL to 1 25 g/100mL, the acidity and viscosity decreased from 101°T to 52°T and 282 mpa·s to 209 mpa·s, respectively, As added penicillin increased from 0 1 I·U/mL to 0 4 I·U/mL, the acidity and viscosity of yoghurt drecreased from 105°T to 47°T and from 286 mpa·s to 213 mpa·s, respectively.