Abstract
Ingestion of different foods containing identical amounts of starch can result in very different postprandial rises in blood glucose and insulin concentrations. Limitation of the early rises in blood glucose and insulin levels seems to be beneficial to human health in the long term. Many studies of starch digestion in vitro are made to understand the molecular basis for differences in digestion rates in vivo to enable prediction of likely rates of digestion of particular starchy foods. Michaelis-Menten kinetics of starch digestibility provides estimates of available (digestible) substrate as starch samples are hydrothermally treated. Combined with studies of starch structure using calorimetry and FTIR spectroscopy, key features influencing rates of amylolysis were identified. Measurement of product formation during prolonged incubations of starch with α-amylase produces digestibility curves. Use of logarithm of slope (LOS) plots to analyse the curves by 1st order kinetics gave values for digestibility rate constants and the total digestible starch, C∞. An important conclusion is that contrary to many reports in the literature, cooked starches do not contain distinct fractions of rapidly and slowly digested material. These kinetic approaches have also been used in studies of plan-tencapsulated starch to understand how cell walls influence access of amylase to starch.