Department of Pediatrics, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil.
J Nutr. 2013 Mar;143(3):302-6. doi: 10.3945/jn.112.166728. Epub 2013 Jan 16.
Cooked white rice (CWR) provides up to 71% of the dietary protein for many people worldwide. The protein digestibility-corrected amino acid (AA) score is the method adopted by FAO/WHO to evaluate protein quality. Our group has proposed the metabolic availability (MA) of AAs as another determinant of protein quality. It measures the percentage of an indispensable AA that is incorporated during protein synthesis. This study is the first to our knowledge to assess the MA of l-lysine (L-Lys) from CWR in humans using the indicator AA oxidation (IAAO) technique. Three amounts of L-Lys, 10, 15, and 19 mg · kg(-1) · d(-1) (= 28.5, 42.8, and 54.3% of the mean L-Lys requirement of 35 mg · kg(-1) · d(-1)), were studied in 5 healthy young men in a repeated-measures design. To test the principle that the Maillard reaction has an effect on the MA of LLys, we also assessed the MA of L-Lys in oven-browned, cooked rice (n = 3) in the amount of 19 mg · kg(-1) · d(-1) L-Lys. The MA of L-Lys was estimated by comparing the IAAO response with varying L-Lys intakes in rice compared with the IAAO response to varying l-Lys intakes in the reference protein (crystalline AA mixture patterned after egg protein) using the slope ratio method. The MA of L-Lys from CWR was high (97%), but the effect of the Maillard reaction reduced it to 70%. The results show that despite its relatively low content in rice, L-Lys has a high MA when the rice is cooked without being browned.
煮熟的白米饭（CWR）为全世界许多人提供高达 71%的膳食蛋白质。蛋白质消化率校正氨基酸（AA）评分是 FAO/WHO 用来评估蛋白质质量的方法。我们小组提出了氨基酸代谢可用性（MA）作为蛋白质质量的另一个决定因素。它衡量的是在蛋白质合成过程中被整合的必需氨基酸的百分比。这项研究是首次使用指示剂氨基酸氧化（IAAO）技术评估 CWR 中 l-赖氨酸（L-Lys）在人体中的 MA。在一项重复测量设计中，我们研究了三种剂量的 L-Lys，分别为 10、15 和 19mg·kg(-1)·d(-1)（分别为 35mg·kg(-1)·d(-1)的平均 L-Lys 需求的 28.5%、42.8%和 54.3%），给 5 名健康年轻男性服用。为了验证美拉德反应对 L-Lys 的 MA 有影响的原理，我们还评估了在烤箱中烤焦的、煮熟的米饭（n=3）中的 L-Lys 的 MA，摄入量为 19mg·kg(-1)·d(-1)L-Lys。通过比较米饭中不同 L-Lys 摄入量与参考蛋白质（模仿鸡蛋蛋白的结晶 AA 混合物）中不同 l-Lys 摄入量的 IAAO 反应，使用斜率比法来估计 L-Lys 的 MA。CWR 中 L-Lys 的 MA 很高（97%），但美拉德反应的影响使其降低到 70%。结果表明，尽管米饭中 L-Lys 的含量相对较低，但如果米饭在不烤焦的情况下煮熟，其 MA 较高。
