Preparation of calcium absorption-stimulating whey protein using Amino-carbonyl reaction

为了考察乳清蛋白与葡萄糖-6-磷酸（G6P）进行Millard反应的最佳条件，将乳清蛋白与G6P在pH 7.0下按不同质量比溶解，冷冻干燥，在50℃和65%的相对湿度下孵育，并测定反应产物的褐变、蛋白质聚合、磷含量。乳清蛋白与G6P的比例为1∶0.3；反应时间小于1天，因为蛋白质的棕色发育和聚合速度过快，孵育0.5天或1天制备的乳清蛋白- g6p偶联物的磷含量高于酪蛋白。用大鼠实验考察了乳清分离蛋白-G6P偶联物对钙吸收的影响。大豆蛋白组、酪蛋白组和WPI-G6P偶联饲粮组小肠结扎袢可溶性钙比例分别为43.2(]SY.+- .[)8.7、72.7(]SY.+- .[)8.0和77.7(]SY.+- .[)9.7。WPI-G6P共轭饲料组小肠可溶性钙含量显著高于大豆蛋白饲料组。这表明WPI-G6P偶联物可溶解钙，防止磷酸钙在小肠中沉淀。大豆蛋白组、酪蛋白组和WPI-G6P偶联饲料组的钙吸收率分别为50.7(]SY.+- .[)17.6、58.5(]SY.+- .[)8.3和72.6(]SY.+- .[)19.7，通过结膜环中<@D145@>D1Ca消失来估算。WPI-G6P偶联饲料组的钙吸收率也高于大豆蛋白饲料组。这些结果表明WPI-G6P偶联物是有用的食品材料。

In order to examined the optimum conditions for the Millard reaction between whey protein and glucose-6-phosphate (G6P) were examined, whey protein and G6P were dissolved at various weight ratios at pH 7.0, freeze-dried, incubated at 50ﾟC and 65% relative humidity, and the browning, polymerization of proteins, the phosphorus content of reaction products were measured. The following conditions were appropriate : the ratio of whey protein to G6P,1 to 0.3 ; reaction time, less than 1 day, because brown color development and polymerization of protein exceed rapidly and the phosphorous content of whey protein-G6P conjugates prepared for 0.5 or 1 day of incubation was higher that of casein. The effect of the WPI (whey protein isolate) -G6P conjugate on calcium absorption was examined using rats. The proportions of soluble calcium in the ligated loop of the small intestine of the soy protein, casein, and WPI-G6P conjugate diet groups were 43.2(]SY.+-。[)8.7,72.7(]SY.+-。[)8.0, and 77.7(]SY.+-。[)9.7, respectively. The soluble calcium in the small intestine was significantly higher in the WPI-G6P conjugate diet group than in the soy protein diet group. This indicated that the WPI-G6P conjugate solubilizes calcium to prevent the precipitation of calcium phosphate in the small intestine. The calcium absorption, which was estimated by the disappearance of <@D145@>D1Ca in the ligated loop, of the soy protein, casein, and WPI-G6P conjugate diet groups was 50.7(]SY.+-。[)17.6,58.5(]SY.+-。[)8.3, and 72.6(]SY.+-。[)19.7, respectively. The calcium absorption was also higher in the WPI-G6P conjugate diet group than in the soy protein diet group. These results suggest that WPI-G6P conjugates are useful as food materials.