生鲜乳中优势嗜冷菌对UHT乳蛋白浓度的影响  

Effect of dominant psychrophilic bacteria in fresh milk on the concentration of UHT Milk protein

作　　者：王辉 邵伟 张少颖 王富兰 王帅 武亚婷 范雪 赵艳坤 WANG Hui;SHAO Wei;ZHANG Shaoying;WANG Fulan;WANG Shuai;WU Yating;FAN Xue;ZHAO Yankun(Xinjiang Key Laboratory of Meat Milk Production Herbivore Nutrition/College of Animal Sciences,Xinjiang Agricultural University,Urumqi 830052,China;Key Laboratory of Agro-Products Quality and Safety of Xinjiang/Institute of Quality Standard and Testing Technology for Agro-Products,Xinjiang Academy of Agricultural Sciences,Urumqi 830091,China)

机构地区：[1]新疆农业大学动物科学学院/新疆肉乳用草食动物营养实验室,乌鲁木齐830052 [2]新疆农业科学院农业质量标准与检测技术研究所/新疆农产品质量安全实验室,乌鲁木齐830091

出　　处：《新疆农业科学》2023年第9期2314-2322,共9页Xinjiang Agricultural Sciences

基　　金：新疆维吾尔自治区自然科学基金项目“hylB介导无乳链球菌对乳腺上皮细胞泌乳功能的调控机制研究”(2019D01B32);国家自然科学基金项目“二元信号系统CovS/CovR对牛源无乳链球菌毒力与耐药的分子调控机制研究”(32060797);新疆维吾尔自治区重大科技专项“乳品质量风险分析与预警技术研究应用”(2020A01001-3);新疆农业大学大学生创新项目(dxscx2021107)。

摘　　要：【目的】研究UHT乳在接入不同数量级的嗜冷菌时,不同储存温度下UHT乳中蛋白浓度的变化。【方法】(1)采用混培法,将原料乳从原液稀释至10-5稀释梯度,每个梯度做2个平行,6.5℃培养10 d,分离纯化保留单个菌落;(2)运用嗜冷菌基因组DNA提取与PCR反应鉴定筛选出优势嗜冷菌;(3)选用乳平板可视鉴定法,筛选出产蛋白酶能力最强的菌株。(4)采用BCA蛋白浓度测定法,将UHT乳稀释8倍、12倍、20倍、24倍、28倍在磷酸盐缓冲液中,测定不同稀释倍数的UHT乳在蛋白浓度测定试验中线性关系最好的稀释倍数。(5)UHT乳同时接入10^(3)、10^(4)、10^(5)CFU/mL的优势嗜冷菌,3组试验组分别在4、7和21℃环境下储存,培养7 d,每24 h BCA蛋白浓度测定法检测一次蛋白浓度。【结果】(1)在33份生鲜乳样品中,共筛选出212株嗜冷菌。(2)假单胞菌为生鲜乳中优势嗜冷菌,分离率为5.19%。(3)99号菌株假单胞菌产蛋白酶能力最强,透明圈带直径为0.3 mm;(4)UHT乳在28倍稀释浓度下的蛋白定量线性系数为R^(2)=0.998,线性关系最好。(5)4℃条件下时,假单胞菌添加量为10^(3)、10^(4)和10^(5)CFU/mL 3个试验组的蛋白浓度变化均不显著(P>0.05);7℃时,3组接菌量的蛋白浓度较对照组均表现差异显著(P<0.05);21℃条件下,除了104 CFU/mL试验组蛋白浓度下降差异显著(P<0.05),10^(3)和10^(5)CFU/mL 2个试验组蛋白浓度下降极显著(P<0.01)。【结论】生鲜乳中嗜冷菌含量、储藏温度、储存时间对UHT乳蛋白浓度均有影响,温度越高、嗜冷菌含量越高,蛋白水解的程度越明显,影响UHT乳的品质。【Objective】To investigate the changes of protein concentration in UHT milk at different storage temperatures when UHT milk was exposed to different orders of cold-philic bacteria.【Methods】(1)Mixed culture method was used to dilute the raw milk from the original liquid to a 10^(-5)dilution gradient,and each gradient was parallel to each other.They were cultured at 6.5℃for 10 days to isolate and purify and retain a single colony.(2)Genomic DNA extraction and PCR reaction were used to identify the dominant cold-philic bacteria.(3)Milk plate visual identification method was used to screen the strain with the strongest protease production ability.(4)BCA protein concentration determination method was applied,UHT milk was diluted 8 times,12 times,20 times,24 times and 28 times dilution concentration in phosphate buffer,and the linear dilution ratio of UHT milk in protein concentration determination experiment was determined.(5)UHT milk was simultaneously inoculated with 10^(3),10^(4)and 10^(5)CFU/mL dominant thermophilic bacteria.The three experimental groups were stored at 4,7 and 21℃for 7 days,respectively.Protein concentration was detected every 24hBCA.【Results】(1)A total of 212 strains of thermophilic bacteria were screened out from 33 fresh milk samples.(2)Through PCR identification,pseudomonas was the dominant cold-philic bacteria in fresh milk,and the isolation rate was 5.19%;(3)Through the milk plate visual identification method,pseudomonas strain 99 showed the strongest protease production ability,and the diameter of the transparent ring was 0.3mm;(3)The linear coefficient of protein quantification in UHT milk aT_(2)8 times diluted concentration was R^(2)=0.998,and the linear relationship was the best.(4)At 4℃,there was no significant change in the protein concentration of the three experimental groups supplemented with 10^(3)CFU/mL,10^(4)CFU/mL and 10^(5)CFU/mL pseudomonas(P>0.05);At 7℃,the protein concentration of the inoculated bacteria in the three groups was significantly different from

关 键 词：生鲜乳 嗜冷菌 蛋白酶 UHT乳 蛋白浓度 

分 类 号：S879.1[农业科学—畜牧兽医]