Effects of Alcalase/Protease N treatments on rice starch isolation and their effects on its properties

The effects of different protease treatments on rice starches and their properties were studied. The rice starches produced from protease N exhibited higher pasting viscosities than those produced from alcalase. The hot pastes of the starches produced from protease N also showed higher elastic moduli, zero-order Newtonian viscosities and yield stresses than those produced from alcalase. No differences were found in the crystalline pattern, thermal properties, granules appearance, and average molecular weight (Mw) of the rice starches between the two protease treatments. But the Mw of the pasted starch produced from protease N was higher than that produced from alcalase. When additional protease was added to the isolated starches and the mixture pasted, the Mw of the starches pasted with added alcalase was significant lower than that of the starches pasted with added protease N. The reduction in molecular weight suggested that alcalase had modified the starch molecules during pasting.