Suitable Harvest Time in Reference to the Changes of Nutritional Component during Cultivation of Bean Sprouts

Studies on Cultivation and Keeping Quality of Bean Sprouts Part IV

Abstract

Bean sprouts were cultured by use of soybean (Glycine max), mung bean (Vigna radiata), and adzuki bean (Vigna angularis) as materials, and suitable harvest time was estimated by considering such factors as degrees of growth, hardness of hypocotyl, and nutritional constituents. Cultivation was conducted under the optimum condition reported in the previous paper; that is, the seeds stored for 6 months at 0°C were immersed in 30°C water for 6 hours and held on sprouting beds which were sprayed 30°C water for 15 minutes every 4 hours. The three kinds of bean sprouts grew up rapidly during 4-5 days after planting (before immersion), after that the hypocotyl showed a slight decrease in diameter and became yellowish. Elongation, too, stopped for a while and the formation of lateral roots and foliage leaves was found 7 days after. Hardness of hypocotyl also increased during first 5 days, then gradually decreased. General tendency of the changes of vitamin C (reduced ascorbic acid), protein, and fat during cultivation was almost similar among the three beans. Vitamin C was synthesized during sprouting and its content increased through 5 days after planting, then slightly decreased. The greater part of vitamin C was found in hypocotyl. While the change of protein content differed between in hypocotyl and in cotyledon, its total content in the bean sprouts decreased rapidly during 4-5 days after planting. Fat content also showed a rapid decrease in a similar manner. The contents of protein and fat were markedly higher in soybean sprouts than in mung bean and adzuki bean sprouts. By considering both external appearance and internal quality, it was concluded that 4-5 days after planting would be an optimum harvest time for three kinds of bean sprouts tested.