Kinetic studies of in vitro digestion of amylosucrase-modified waxy corn starches based on branch chain length distributions

Abstract

Classification of starch into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS) has been in controversy. Therefore, this study aimed to ascertain the individual existence of RDS and SDS using amylosucrase-modified starch. Enzymatic hydrolysis curves of modified waxy corn starches were obtained and fitted to a logarithm of slope (LOS) plot. LOS plots for amylosucrase-modified starches revealed a discontinuity, reflecting the change of rate constant k during digestion, such that distinguishable k s for each of the phases were defined (kRDS, kSDS). The LOS plot approach could be utilized as a persuasive basis for the classification of the starch fractions. The structure of amylosucrase-modified starches was characterized before and after removal of RDS and/or SDS. Branch chains with certain lengths contributed to the organization of each fraction and determined the primary crystallite configuration of amylosucrase-modified starches causing the diversity of digestion properties.