豆奶蛋白组分和胰蛋白酶抑制剂活性的热变化

CHANGES OF SDS-PAGE PATTERNS OF SOYMILK PROTEIN AND TRYPSIN INHIBITOR ACTIVITY INDUCED BY HEATING

目的 : 研究热处理对豆奶蛋白组分、巯基含量及胰蛋白酶抑制剂活性的影响。方法 : 以 95℃、1 2 0℃、1 40℃处理鲜豆奶 ,用 SDS- PAGE(十二烷基磺酸钠 -聚丙烯酰胺薄板凝胶电泳 )分析经热处理和 β-巯基乙醇处理后豆奶蛋白组分的变化 ;研究豆奶胰蛋白酶抑制剂活性的热变化 ;用 Ellman试剂法测定巯基含量。结果 : 鲜豆奶中 7,8,1 1 ,1 2 ,1 3,1 4,1 5,1 6号蛋白组分经热处理后逐步消失 ,出现分子量为 1 0 4 62 0的 1 7号蛋白质新组分 ,β-巯基乙醇处理证明此蛋白组分的出现与 1 2 ,1 3,1 4,1 5,1 6号蛋白组分的消失具有相关性 ,这些组分的次级结构主要靠二硫键结合 ;热处理使豆奶巯基含量急剧下降 ;热处理失活 90 %的胰蛋白酶抑制剂 ,95℃处理需要 35min,1 2 0℃需 7min,而 1 40℃只需 60 s左右。结论 : 热处理导致豆奶蛋白巯基的变化从而引起蛋白组分的变化 ;胰蛋白酶抑制剂的热致死时间曲线表明 ,在 95～ 1 40℃范围内 ,温度增加 30℃ ,钝化90 %胰蛋白酶抑制剂的热处理时间缩短为原来的 1 /1

Objective: To evaluate the heating effects on SDS PAGE patterns of soymilk protein, trypsin inhibitor activity and sulfhydryl bond content in soymilkMethods: Soymilk samples were heated at 95 ℃,120 ℃ and 140 ℃.SDS PAGE was adopted to detect the pattern changes of soymilk proteins after heating and β mercaptoethanol pretreatment. Trypsin activities were analyzed to detect the changes of trypsin inhibitor activities. Ellman method was used to detect sulfhydryl bond.Results: The protein bands of 7,8,11,12,13,14,15,16 disappeared and one new band(band 17)with Mr of 104 620 appeared in the SDS PAGE pattern of soymilk proteins after heated at 95 ℃,120 ℃ and 140 ℃. The sulfhydryl bond content decreased after heating and this change contributed to the pattern change of soymilk protein by β mercaptoethanol pretreatment and by determining the sulfhydryl bond content. The holding time to inactivate 90% of soy bean inhibitor activity at 95 ℃ ,120 ℃ and 140 ℃ were 35 min, 7 min and 60 s respectively.Conclusion: Heating treatment may change the sulfhydryl bond and SDS PAGE pattern of soymilk proteins. The TDT curve indicates that the holding time required to inactivate 90% of soybean trypsin inhibitor could be reduced ten folds by raising 30 ℃ within the temperature range of 95 140 ℃.