Abstract
Bean cured refuse is major sub-product of tofu; it has been a foodstuffs with plentiful nutrition, but presently it is mostly disposed to be reclaimed or burned. In the present study we aim to dissolve the bean curd refuse by applying the super- or sub- critical water as the reaction solvent under a high temperature and high pressure and to extract useful components from the dissolved products. We applied the super- or sub-critical water to the bean curd refuse at an approaching temperature of 200-450°C and pressure of 15-30 MPa in a high pressure vessel under a batch operation. It is found that rapid heating, short reaction time and lower temperature (up to 250°C) in the sub-critical water treatment are favored for selective production of sugars. Maximum amounts of organic acids and alcohols were produced at an operating temperature of 300°C in the pressure range of 15 to 30 MPa. At an operating temperature exceeding 300°C, amount of solid residue decreased to about 5% on the elemental carbon basis. At operating temperatures beyond 350°C (mainly at supercritical range) amount of gaseous products exceeded 30%.
