赖氨酸、蛋氨酸、缬氨酸及苏氨酸在大米粒中的分布及其适宜碾磨度

米粒经手工剥离为“果种皮+糊粉层”、“胚+吸收层”和胚乳三部分,并测定了各部分的蛋白质、赖氨酸、缬氨酸、苏氨酸和蛋氨酸含量。同时观察了实验室加工和工厂加工条件下不同碾磨度对各部分丢失和氨基酸含量的影响。结果显示:果种皮、糊粉层、胚和吸收层等部分虽只占米粒重量的7.27～8.42％,但其蛋白质、赖氨酸、蛋氨酸、缬氨酸和苏氨酸分别占总量的14.05～15.77、29.0～30.5、11.83、16.75和18.4％。在工厂或实验室加工条件下,稻米经碾磨后,米粒中所观察的各成分都有改变,其中赖氨酸含量下降最显著。本文对稻米的适宜碾磨度问题进行了讨论,认为在目前工厂加工条件下,以不超过九二米碾磨度为宜;过分的精白米会降低谷类蛋白质的营养价值。

THE DISTRIBUTION OF LYSINE,METHIONINE,VALINE AND THREONINE IN WHOLE RICE GRAIN IN RELATION TO THE DEGREE OF MILLING IN MODERATION

Whole rice grain was dissected by hand into fractions of pericarp, ale-urone, scutellum, embryo and endosperm. For the convenience of having enough amount of samples for amino acids assay some of which were recom-bined and finally three parts, pericarp aleurone layer, scutellum embryo and endosperm, were obtained. Protein, lysine, methionine, threonine and valine contents were determined for each part. The data obtained indicated that although total weight of the first two parts accounted for only 7.27-8.43% of the whole grain, they contributed 14.5-15.8% protein, 29.0-30.5% lysine, 11.8% melhionine, 16.8% valine and 19.4% threonine, contained in the whole grain. During husking process it indicated that the lesser amounts of pericarp, aleurone, scutellum and embryo were retained and the larger percentage of protein and lysine was lost. This fact was identified either by a specially designed miller in the laboratory or a commonly used sand wheel miller in the factory. The suitable degree of milling for rice was discussed and it was proposed that 92% extration for rice rather rational.