以有效赖氨酸含量评价大豆蛋白中赖氨酸损伤程度的研究

Study on the estimation of lysine damage of soy protein byavailable lysine conten

采用两种化学方法测定的有效赖氨酸来判断经与葡萄糖共热处理或碱性热处理的大豆蛋白中的赖氨酸损伤程度，并与常规法测定的总赖氨酸进行了比较，发现有效赖氢酸含量不仅明显低于总赖氨酸，而且在处理过程中的下降速度更快；在与葡萄糖共热处理过的大豆蛋白中，胍化法测定的有效赖氨酸含量仅为总赖氮酸的２５％，处理损失率高达７８％－８５％，而糠醛赖氨酸法测定的有效赖氨酸损失率为４８％－８０％，总赖氨酸损失率则为１７％－４０％。在经碱性热处理的大豆蛋白中，有效赖氨酸（胍化法）含量也明显低于总赖氨酸，损失率约为后者的２倍。研究结果表明，用胍化法测定的有效赖氨酸来判断大豆蛋白质的赖氨酸损失程度较为可靠。

Available lysine content measured by two chemical assays was used for evaluating thelysine damage in soy proteins heated either with glucose or in alkaline mediurn as compared withthe total lysine measured by ordinary analysis. Available lysine content was significantly lowerthan total lysine and decreased rapidly in the process of treatment.When soy protein was heatedwith glucose,available lysine measured by guanidination method was only abnut 25%of the totallvsine with a loss of 78%- 85%in contrast with the loss of 48%- 80%for avallable lysine byfurosine rnethod aid 17%一40%for total lysine. When soy protein was heated in alkaline med- um,available lysine content was also much lower than the total lysine and lost about twice that ofthe lysine. The results demonstrated that available l ysine rneasured by guanidInation method wasmore reliable in evaluating the damage in soy proteins.