AMYLOLYSIS OF WHEAT STARCHES IN RELATION TO AMYLOSE CONTENT

摘要

The susceptibility of starch granules to degradation by amylases depends on the source of the starch granules and of the amylase (Planchot et al., 1995). While many studies have described varying digestion kinetics and degradation patterns by alpha-amylases with starches from different botanical sources, there is much less information on the variability in digestion of different starch varieties of the same botanical origin. Kinetic parameters of porcine pancreatic alpha-amylase acting on starches from different botanical sources have been shown to vary significantly (Slaughter et al., 2001). The rate and extent of alpha-amylolysis of granular starch is mainly determined by physiochemical parameters of the granule, such as granule size, available surface area, crystallinity, amylose to amylopectin ratio, accessibility, porosity, structural inhomogeneities and degree of integrity (Jacobs et al., 1998). Factors limiting enzymic hydrolysis are water diffusion in the granule and adsorption of the enzyme on the starch molecules. Proteins and lipids attached to the surface of starch granules have also been shown to limit the accessibility of the substrate to a-amylase.