菜用大豆，又称毛豆，作新鲜豆类蔬菜食用，主食鲜籽粒。毛豆豆荚内包裹豆粒的白色豆衣(荚皮内膜层或豆荚内果皮)的多少，直接影响消费者对毛豆豆荚新鲜程度的判断，是评价毛豆品种外观品质性状之一。本文首次以毛豆最佳采收期的豆仁外白色豆衣为实验材料，利用氨基酸自动分析仪，对其游离氨基酸组成及含量进行了测定与分析。结果发现：在最佳采收期，白色豆衣多少因毛豆品种而不同；白色豆衣内含量较高的游离氨基酸依次为谷氨酸、γ-氨基丁酸、丙氨酸、丝氨酸、天冬氨酸，为76.051~839.804 μg/g；包含2种典型的呈鲜味氨基酸：谷氨酸和天冬氨酸，占总游离氨基酸总量65.246%；包含1种具有生理活性功能的特殊氨基酸：γ-氨基丁酸，含量190.659 μg/g。本研究结果初步明确了毛豆白色豆衣内主要呈鲜味游离氨基酸成分及含量，对菜用大豆品质育种具有一定的理论指导意义。
Vegetable soybean, also known as green soybean, is consumed as one leguminous vegetable. The quantity variance of white bean coat (membranous endocarp of pod wall or pod endocarp) outside the fresh grain, as one of the appearance quality traits, directly affects consumers’ judgments about the degree of freshness of vegetable soybean pod. In this study, the free amino acids in white bean coat were detected by automatic amino acid analyzer. The results showed that the quantity variance of white bean coat depended on the different varieties; the content of free amino acids ranged from 76.051 to 839.804 μg/g, including glutamic acid, γ-aminobutyric acid, alanine, serine and aspartic acid; the umami amino acids accounted for 65.246% of the total free amino acids, including glutamic acid and aspartic acid; the content of γ-aminobutyric acid with special physiological function was 190.659 μg/g. The data generated preliminarily clarified the composition and content of umami amino acids in pod endocarp and provided the theoretical basis for quality breeding of vegetable soybean.
