食物中色氨酸测定方法的改进

本文报告用氰离子激活木瓜蛋白酶水解玉米、大米、小米、小麦、大豆、代乳粉、浓缩鱼蛋白及酪蛋白8种食物样品的蛋白质,测定了色氨酸含量。根据色氨醛反应原理用含27mg％FeCl_3·6H_2O和2％乙酸酐的冰醋酸溶液与等量30N硫酸混合作显色剂,将样品水解液与色氨酸标准液分别加显色剂后,在545nm波长下比色。在光径1cm时,灵敏度为0.2μg。选用30种不同品种玉米作对照测定,加氰离子的色氨酸平均测定值比不加氰离子的平均值增高18.6mg％,差异非常显著(P<0.001)。

AN IMPROVED METHOD FOR THE DETERMINATION OF TRYPTOPHANE IN FOODS

An improved method was described for the determination of tryptophane in foods (maize, rice, millet, wheat, soybean, milk powder substitute, fish protein concentrate and casein) hydrolyed by cyanide-activated papain. The color-deyeloping agent was a mixture of equal volume of 30N sulfuric acid and glacial acetic acid containing 2% acetic anhydride and 27mg% FeC13.6H2O, and its intensity was measured with spectrophotometer at absoption maximum 545nm. The sensitivity was 0.2μg of tryptophane per ml of tested solution through 1cm length. The recovery was found to be between 96-104%. By comparing noncyanide and cyanide-activated papain for analysis of varieties of maize the mean tryptophane values were 50.1 mg% and 68.7mg% respectively, and the difference was very significant (p<0.001). Thus cyanide-activation of papain should not be omitted in this procedure. This improved method for the determination of tryptophane recommended herewith is simple, reproducible and convenient in food analysis.