Improvement of Bean Sprouts Production by Intermittent Treatment with Carbon Dioxde

For the purpose of improving bean sprouts production, the effects of intermittent, short time CO2 treatment on the growth and quality of the bean sprouts of soybean, mung bean and adzuki bean examined. Three kinds of mixed gases containing 600, 800 and 1200ppm of CO2 were prepared. CO2 treatment was performed by introducing the mixed gases into the sprouting bed for 60 minutes a day for consecutive 7 days, beginning 12 hours after the start of cultivation. The CO2 treatment greatly affected the growth and quality of bean sprouts; the CO2 treatment at 600 and 800ppm markedly stimulated the elongation and thickening of hypocotyls, thus enabling the production of socalled "futomoyashi" or high quality thick bean sprouts with gloss, semi-transparency, and substanti- ality. Also the treatment greatly elevated the vitamin C content in the bean sprouts, remarkably improving the marketability of the bean sprouts together with the favorable effects described above. It was assumed that the most appropriate harvesting time for the bean sprouts treated with 600 and 800ppm of CO2 was about 3 days after planting, when the length and thickness of bean sprouts fulfilled the marketability standard, the vitamin C content was greatly elevated, and both the hardening of hypocotyls and the development of lateral roots were moderate. Consequently, the cultivation period was shortened by 3-4 days compared to the conventional method. On the whole, it was concluded that 600ppm was the optimum CO2 concentration in treating bean sprouts, although no significant differences in effectiveness were observed between 600 and 800ppm. In the conventional method of culture, unfavorable levels of CO2 may accumulate over long periods, giving a harmful effect. It may be helpful to improve the method of culture by aerating the chamber and adding CO2 for a short period each day.