摘要:
通过测定发酵过程中牦牛酸乳和牛酸乳的pH、酸度、质构、双乙酰和乙醛含量,分析两种酸乳在发酵过程中品质特性的变化规律。在整个发酵周期内,牦牛酸乳和牛酸乳的酸度呈上升趋势,pH则相应下降,两种酸乳之间无显著差异(p>0.05)。牦牛酸乳和牛酸乳在发酵0~3 h内质构特征几乎无变化,3~11 h内硬度、稠度、黏聚性和黏性指数显著上升(p<0.05),11 h之后各项指标变化不显著(p>0.05),且牦牛酸乳的质构指标均高于牛酸乳。两种酸乳的双乙酰和乙醛含量在前发酵期内显著上升(p<0.05),在后发酵期内出现一定波动但逐渐趋于稳定(7~11 mg/L),且牦牛酸乳与牛酸乳之间无明显差异。结论:在整个发酵周期(20 h)内,牦牛酸乳和酸乳的品质特性变化规律相同,除质构指标外其它测定指标无显著差异。
关键词:
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牦牛乳和牛乳
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酸乳
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发酵
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品质特性
Abstract:
The changes of quality characteristics of yogurt made from yak milk and cow milk were analyzed through measuring the pH,total acidity,texture,diacetyl and acetaldehyde contents during the fermentation. During the whole fermentation period,total acidity of yak yogurt and cow yogurt showed an increase trend,while the pH decreased accordingly,and there were no significant differences between the two kinds of yogurt(p>0.05). The texture properties of the two kinds of yoghurt did not change during 0~3 h,and the hardness,consistency,cohesiveness and viscosity increased significantly during 3~11 h(p<0.05),thereafter these four texture properties changed unsignificantly(p>0.05). The texture properties of yak yogurt were higher than that of cow yogurt. The diacetyl and acetaldehyde contents of the two kinds of yogurt increased significantly during the pre-fermentation stage(p<0.05),and there was a certain fluctuation in the post-fermentation stage keeping at 7~11 mg/L. There were no obvious differences between yak yogurt and cow yogurt in diacetyl and acetaldehyde contents. Conclusion:For two yogurts made from yak milk and low milk,the change regularities of quality characteristics were same during the whole fermentation period,and there were no significant differences between the two kinds of yogurts in the tested indexes except for texture indexes.
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