不同热分级脱脂奶粉中乳清蛋白热变性聚合物分析

Analysis of aggregations in different heating degree skim milk powders

为了解不同受热程度脱脂乳粉中乳蛋白各组分以及各组分之间的变化规律,利用还原型和非还原型聚丙烯酰胺凝胶电泳(SDS-PAGE)对乳清蛋白氮指数(WPNI)分别为7.08、4.24、1.45的不同受热程度脱脂乳粉进行蛋白组分分析。结果表明,不同受热程度乳粉形成的大分子聚合物组成和含量差异显著,低温加热脱脂乳粉中乳清蛋白变性程度最低,形成的大分子聚合物较少而高温加热脱脂乳粉中乳清蛋白变性程度较大,形成的大分子聚合物较多。利用还原型SDS-PAGE对不同受热程度脱脂乳粉的电泳胶片中大分子聚合物进行分析可知,不同受热程度脱脂乳粉形成的聚合物组成大致相同,但含量差异显著。β-Lg和κ-酪蛋白参与了几乎所有的聚合反应。形成的大分子聚合物分子量≥200 ku。

The sodium dodecyl sulfate polyacrylamide gel electrophoresis（SDS-PAGE） was used to analyze the protein of skim milk powders with different heating degree. The whey protein nitrogen index （WPNI） were 7.08, 4.24 and 1.45 respectively.The result showed that the composition and content of aggregations in different heating degree milk powders was quite different and the whey protein denaturation de- gree of the low heating treated skim milk powder was lower than others and the large particle aggregations was the least. On the contrary, the high heating treated skim milk powder formed maximum aggregations. The large particle aggregations was analyzed by reduced SDS-PAGE and the result showed that the components of different heating degree skim milk powders were almost the same but the content was signifi- candy different..β-Lg and K-casein was involved in？almost all the？polymerizations.The molecular weight of macromolecule aggregations were larger than 200 ku.