An opportunity to engineer nutritional properties of foods by structure engineering

With most starchy foods the rate of enzymatic digestion of starch is a key determinant of the glycaemic response.Many food factors that reduce the rate of amylolysis, also lower total starch digestibility in the small intestine.In a whole cereal grain the intact cell walls protect starch from digestion.The characteristics of starch per se and heating conditions are also of crucial importance.Starch granules that are only slightly gelatinized are less hydrolyzed by a-amylase than starch granules that are more gelatinized. Further heating can decrease accessibility of starch granules to hydrolysis, because amylose will leach out of starch granules.We have studied the effect of processing on the microstructure of cell walls and starch.Malting caused cell wall degradation, but starch was not gelatinized.Autoclaving did not break cell walls, but starch was gelatinized.Milling liberates starch from cells and organic acids and heat treatment affects greatly the degree of starch swelling.The degree of starch hydrolysis by a-amylase can be engineered by processing.