Decomposition Kinetics of Bean Curd Refuse in Hot Compressed Water at Saturated Steam Pressure

Decomposition of bean curd refuse (Okara) was examined in hot compressed water at saturated steam pressure from 423 to 573 K. Bean curd refuse was fragmentated in water above ca. 423 K. The decomposition of bean curd refuse rapidly proceeded and almost finished within about 10 min at 473 K at which the yield of water soluble fraction attained about 45 carbon %. The conversion rate from water insoluble fraction to water soluble increased with increasing temperature and most of the bean curd refuse became water soluble fraction or acetone soluble one at 573 K. The yield of total saccharides was up to 38% and a large part of hemicellulose and cellulose in bean curd refuse would be able to become saccharides. Furthermore, water promoted the decomposition of water insoluble fraction to water soluble and 10 times of water relative to bean curd refuse by weight basis was enough for this promotion. The shaking of the reactor promoted the decomposition of bean curd refuse to both lower and higher molecular weight sides. Hot compressed water can be a useful solvent for the decomposition of bean curd refuse by the proper choice of temperature and amount of water.