一种牦牛曲拉干酪素的结构及功能性质  

Structural and functional properties of casein made from yak Qula

作　　者：何林枫 蔡丽莎 杨宽 曾珍[1] 李诚[1] HE Lin-feng;CAI Li-sha;YANG Kuan;ZENG Zhen;LI Cheng(College of Food Science,Sichuan Agricultural University,Ya’an 625014,China)

机构地区：[1]四川农业大学食品学院,四川雅安625014

出　　处：《江苏农业学报》2020年第3期709-719,共11页Jiangsu Journal of Agricultural Sciences

基　　金：四川省重点研发项目(农产品精深加工类)(2018NZ0033)。

摘　　要：为了研究牦牛曲拉干酪素的结构及功能性质,以牦牛曲拉为原料,将胃蛋白酶、木瓜凝乳酶、酵母凝乳酶复配成复合凝乳酶,用混合凝乳酶制备牦牛曲拉干酪素,对牦牛曲拉干酪素的基本成分、氨基酸组成、蛋白质组成、红外光谱特性、圆二光谱特性、变性温度等进行分析,并模拟食品加工体系中的不同温度、pH值,观察其对牦牛曲拉干酪素功能性质的影响。结果表明,牦牛曲拉干酪素中谷氨酸含量最高,必需氨基酸含量占总氨基酸含量的42%;十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(Sodium dodecyl sulfate-polyacrylamide gel electrophoresis,SDS-PAGE)测定结果表明,牦牛曲拉干酪素蛋白质的相对分子质量主要分布在25000~37000。用红外光谱分析检测得到-NH、C=O等特征官能团,用圆二色光谱鉴定得出,牦牛曲拉干酪素是无规则卷曲型蛋白质,其中α-螺旋占11.3%,β-折叠占26.8%,β-转角占23.3%,无规则卷曲占38.6%。研究结果还表明,牦牛曲拉干酪素的热稳定性较高,变性温度达到123℃左右。牦牛曲拉干酪素的主要功能特性如下:当温度接近50℃时,具有优良的溶解性、乳化性、发泡稳定性;在较高温度(50~70℃)下,持油性、发泡能力明显增强;在pH值为3~11条件下,除等电点(pH值=4.6)外,有较优良的功能特性;在中性条件下,干酪素溶液的表观黏度最大,最小凝胶含量最低。To characterize the structural and functional properties of casein made from yak Qula by complex rennin containing pepsin,chymopapain and yeast rennin,the basic components,amino acid composition,protein composition,infrared spectroscopy,circular dichroism and denaturation temperature of the casein were studied.Different temperatures and pH values in food processing system were simulated to observe the effects on functional characteristics of casein made from yak Qula.The results showed that the content of glutamic acid was highest in casein,and the content ratio of essential amino acids to total amino acids was 42%.The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)indicated that the relative molecular weight of casein protein in yak gula mainly ranged from 25000 to 37000.The functional groups such as carbonyl and imino groups were detected by infrared spectrum analysis.The results of circular dichroism chromatography showed that casein was a kind of random coil protein,and it was found that theα-helix accounted for 11.3%,theβ-fold accounted for 26.8%,theβ-corner accounted for 23.3%,and the random coil accounted for 38.6%.In addition,casein showed high thermal stability with the denaturation temperature of 123℃.The main functional characteristics of casein made from yak Qula are as follows:the casein has excellent solubility,emulsification and foaming stability when the system temperature is close to 50℃;the oil-holding and foaming capacity of casein are significantly enhanced at relatively higher temperature(50-70℃);when the pH value was 3.0-11.0,except for the isoelectric point(pH=4.6),the casein has excellent functional properties;the rheological properties are optimal under neutral condition.

关 键 词：牦牛 曲拉 干酪素 结构性质 功能性质 

分 类 号：TS252.53[轻工技术与工程—农产品加工及贮藏工程]