Effect of cell wall degrading enzymes on the cooking properties of milled rice and the texture of cooked rice.

Abstract

Effect of the partial degradation of endosperm cell walls on the cooking properties of rice grains and also on the texture of cooked rice was examined by using two different enzyme preparations, i.e., crude enzyme from Aspergillus japonicus and purified endoxylanase from Streptomyces sp. E-86. Texturometer analysis showed that the partial degradation of the cell walls softened the cooked rice grains and made them more sticky. When the excess water was supplied, cooked rice grains expanded more after the enzyme treatment. Moreover, this treatment affected the amylogram of milled rice flour and lowered its viscosity, especially in the retrogradation process. Purified endoxylanase showed these effect without any other enzyme, suggesting the important role of hemicellulosic polysaccharides for the physical properties of endosperm cell walls.