A new combined methodology for obtaining relations between starch molecular structure and digestion kinetics of starch-based foods is illustrated using published data on cooked rice. Digestibility data are treated with the logarithm of slopes method, giving region(s) where first-order loss kinetics are applicable; accurate values for the rate parameters are obtained by non-linear least-squares. A new method is developed to find independent structural variables for whole and enzymatically-debranched starches. Chain-length distributions of amylose and amylopectin are fitted with models using biologically-meaningful parameters, including accounting for SEC band broadening. While slower digestion rate usually means higher residual starch, this is not always so; both digestion parameters must be considered separately. The treatment shows that digestion kinetics depend on amylose content and also amylose molecular fine structure: the amount of shorter amylose chains and total amylose molecular size. The new combined data-treatment methodology is applicable to a wide range of food systems.
Keywords: Amylopectin; Amylose; Biosynthesis; Molecular structure; Rice; Size exclusion chromatography; Starch digestibility.
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