Analysis of the Influence of Different Refrigeration Conditions on the Quality of Yak Milk
Objective:To analyze the effect of different refrigeration conditions on the quality of yak milk.Methods:The raw milk of the same healthy lactating yak in a farm in Xizang Autonomous Region was selected as the test object,and was refrigerated at three different temperatures,namely-20℃,-40℃,and-80℃.The effects of different refrigeration conditions on the quality of yak milk were analyzed and discussed.Results:The results showed that the pH and thermal stability of yak milk refrigerated at-80℃were significantly higher than those refrigerated at-20℃and-40℃(P＜0.05),and the bacterial count of yak milk refrigerated at-80℃was significantly lower than those refrigerated at-20℃and-40℃(P＜0.05).Moreover,the lower the refrigeration temperature,the higher the milk pH and thermal stability,and the lower the bacterial count in the milk.The distribution width of fat particle size,protein hydrolysis degree,soluble protein content,total protein content,red green intensity,and brightness of yak milk refrigerated at-20℃,-40℃,and-80℃showed significant differences(P＜0.05);There were significant differences in the tissue status,taste,and color of yak milk stored at-20℃,-40℃,and-80℃(P＜0.05);The lower the refrigeration temperature,the better the sensory evaluation of the odor of yak milk.Conclusion:The quality of yak milk under-80℃refrigeration conditions is the best,which provides a reference basis for extending the shelf life of yak milk and processing dairy products in the future.
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