不同冷藏时间牦牛乳中细菌群落结构和理化性质比较

Comparison of Bacterial Communities and Physicochemical Properties in Yak Milk with Different Cold Storage Durations

低温贮藏有利于确保原料乳质量,然而也面临原料乳中嗜冷菌增多的风险,因此,了解不同冷藏时间原料乳中细菌群落结构变化对乳品工业持续发展具有重要意义。为此,该试验利用高通量测序技术和乳成分分析仪,分析和比较了4℃下贮藏24、72 h牦牛乳的细菌群落特征和理化特性。结果表明:冷藏24、72 h牦牛乳中第一、二优势菌属为乳球菌属、金黄杆菌属,该两类菌属的细菌分别占到冷藏24、72 h牦牛乳中细菌相对丰度的59.48%和67.51%。冷藏72 h牦牛乳中乳球菌属、金黄杆菌属相对丰度比冷藏24 h牦牛乳高出22.74%、3.56%,但是冷藏72 h牦牛乳中链球菌、不动杆菌属呈现降低趋势。冷藏24、72 h牦牛乳中假单胞菌属相对丰度较低,分别为1.69%和1.78%。冷藏72 h牦牛乳中酪蛋白、脂肪含量低于冷藏24 h牦牛乳,酸度增加到14.66°Τ。72 h的低温冷藏有助于控制牦牛乳细菌繁殖,维持乳品质。该研究为牦牛乳贮藏,干酪等乳制品加工,确保其品质和质量安全提供了理论依据。

Refrigerated storage helps to ensure the quality of raw milk;however,it can also increase the risk of psychrophilic bacteria propagation.Therefore,investigation of bacterial communities of raw milk under different refrigeration durations is crucial to the sustainable development of the dairy industry.This study compared the characteristics of bacterial communities and physicochemical properties of yak milk stored at 4℃for 24 h and 72 h through high-throughput sequencing and by using a milk composition analyzer.The results revealed that the two dominant bacteria in yak milk for both refrigeration durations were Lactococcus and Chryseobacterium,which together accounted for 59.5%and 67.51%of the relative abundance of bacteria in yak milk refrigerated for 24 h and 72 h,respectively.The relative abundances of Lactococcus and Chryseobacterium in yak milk were 22.74%and 3.56%higher,respectively,after 72 h of refrigeration than those in yak milk after 24 h of refrigeration.However,after 72 h of refrigeration,Streptococcus and Acinetobacter in yak milk showed a decreasing trend.The relative abundance of Pseudomonas in yak milk refrigerated for 24 h and 72 h was 1.69%and 1.78%,respectively.Casein and fat levels of yak milk refrigerated for 72 h were lower than those of yak milk refrigerated for 24 hours,and acidity increased to 14.66°Τ.Refrigeration for 72 h is helpful in controlling the reproduction of bacteria in yak milk to maintain milk quality.This study provides a theoretical basis for the storage of yak milk and processing of dairy products,such as cheese,to ensure quality and safety.