蛋清肽及肽钙配合物的制备

Preparation of Calcium-chelating Egg White Peptide

为获得高生物效价的补钙制剂及提高蛋清蛋白的附加值,首先对鸡蛋清进行酶法改性,筛选实验用酶,采用正交试验,分别对酶解条件及肽钙反应条件进行优化,并采用红外光谱法比较反应前后图谱的变化。结果表明:选择先碱性蛋白酶后中性蛋白酶进行双酶酶解,酶解条件为底物质量分数6%、碱性酶酶底比1:100、pH8.0、酶解时间3h;中性酶酶底比1:25、pH7.0、酶解时间3h。制备肽钙配合物最优反应条件为肽钙(CaCl2)质量比2.5:1、pH9.5、底物质量分数4%、温度55℃,在此条件下,可溶性钙含量为21.15mg/L,水解度为8.66%。制备蛋清肽时,使用双酶的水解效果优于单酶,蛋清肽与钙形成了双单齿配合物,其钙质量分数为8.75%。

In order to develop a kind of calcium supplement with high bioavailability,and improve added value of egg white protein,egg white was enzymatically modified and then chelated with calcium.Enzyme screening for the modification of egg white showed that the optimum hydrolysis mode for egg white was sequential hydrolysis with alcalase and neutrase.After this,process optimization for the enzymatic modification of egg white and chelating reaction between modified egg white and calcium was conducted using orthogonal array design.The optimal conditions for the stepwise double enzymatic hydrolysis of egg white were substrate concentration of 6%,alcalase/substrate ratio of 1：100,hydrolysis pH of 8.0 and hydrolysis time of 3 h;neutrase/substrate ratio of 1：25,hydrolysis pH of 7.0 and hydrolysis time of 3 h.In addition,the optimal preparation conditions for calcium-chelating egg white peptide were the ratio between peptide and CaCl2（m/m） of 2.5：1,reaction pH of 9.5,substrate concentration of 4%,and reaction temperature of 55 ℃.Under the optimal conditions,the yield of soluble calcium and degree of hydrolysis were 21.15 mg/L and 8.66%,respectively.Therefore,sequential dual-enzyme hydrolysis method is better than single-enzyme hydrolysis method for the preparation of egg white peptide.The obtained egg white peptides can form a kind of bridging bidentate complex with calcium.The calcium content in the calcium-chelating egg white peptide was up to 8.75%.