牦牛乳和犏牛乳的凝乳特点及乳清中蛋白质组成  

Coagulation characteristics of yak and cattle-yak milk and protein composition of whey

作　　者：康吉草 马煜 廖焕杰 黄林[1] 金素钰[1] 郑玉才[1] KANG Jicao;MA Yu;LIAO Huanjie;HUANG Lin;JIN Suyu;ZHENG Yucai(School of Animal and Veterinary Sciences,Southwest Minzu University,Chengdu 610041,China)

机构地区：[1]西南民族大学畜牧兽医学院,四川成都610041

出　　处：《西南民族大学学报(自然科学版)》2025年第2期135-139,共5页Journal of Southwest Minzu University(Natural Science Edition)

基　　金：四川省应用基础项目(006JB-117)。

摘　　要：为比较牦牛乳和犏牛乳的凝乳特点,并探索乳清蛋白质组成对凝乳的影响,在麦洼牦牛全乳(n=5)和犏牛(n=5)全乳中加入凝乳酶,观察凝乳并通过离心获得酶乳清,采用等电点沉淀法制备酸乳清,用SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)分析乳清蛋白组成.结果表明,牦牛全乳具有良好的凝乳性能,全部牦牛乳及3个犏牛乳中加入凝乳酶后均能凝乳,而犏牛乳有两个样品需要补加凝乳酶后方能凝乳;乳清蛋白组成分析表明,与酸乳清比,酶乳清中酪蛋白(CN)相对比例极显著降低,其他组分除α-乳清蛋白(α-La)外均极显著增加(P<0.01);牦牛乳与犏牛乳的乳清蛋白组成差异主要体现在残留的CN以及两种未知的低分子量蛋白质上,其中牦牛两种乳清中的残留CN和酶乳清中的未知蛋白1(可能为κ-酪蛋白巨肽,CGMP)的比例高于犏牛乳清,而酸乳清中的未知蛋白2则相反.凝乳时间长的两个犏牛乳样,其酶乳清蛋白电泳凝胶中,在31.9 kDa处有条带,提示乳清蛋白组成对凝乳有很大影响.研究结果初步表明,牦牛乳的凝乳特性优于犏牛乳,牦牛乳的凝乳时间短可能与乳中更多的κ-酪蛋白被凝乳酶水解有关.This study aimed to compare the curd characteristics of yak milk and cattle-yak milk,as well as to investigate how the composition of whey protein affected curd formation.To achieve this,rennet was added to whole milk samples from Maiwa yaks(n=5) and cattle-yaks(n=5).The curd was observed,and whey was obtained through centrifugation.Concurrently,acid whey was prepared using the isoelectric precipitation method.Finally,the whey protein composition was analyzed using SDS-polyacrylamide gel electrophoresis(SDS-PAGE).The results indicated that yak whole milk displayed good coagulation performance.All yak milk samples and three cattle-yak milk samples coagulated after adding rennet,while two cattle-yak milk samples required additional rennet to achieve coagulation.The analysis of whey protein composition revealed that the relative proportion of casein(CN) in the enzyme whey was significantly lower than that in the acid whey,whereas other components excepting α-lactalbumin(α-La),showed significant increases(P< 0.01).The differences in whey protein composition between yak milk and cattle-yak milk were primarily observed in the residual CN and two unknown low molecular weight proteins.The proportion of residual CN and unknown protein 1(possibly κ-casein macropeptide,CGMP) in yak whey was higher than that in cattle-yak whey,while the proportion of unknown protein 2 in acid whey showed the opposite trend.Two yak milk samples with longer curd-formation times exhibited a band at 31.9 kDa on the enzyme whey protein electrophoresis gel,suggesting that the composition of whey protein significantly influences curd formation.This study preliminarily demonstrated that the coagulation characteristics of yak milk are superior to those of cattle-yak milk,and the shorter coagulation time of yak milk may be associated with a higher degree of hydrolysis of κ-casein in milk by rennet.

关 键 词：牦牛 犏牛 乳 凝乳 电泳 乳清蛋白 乳腺代谢 

分 类 号：S823.91[农业科学—畜牧学]