Pectin interaction with thermally modified starch affects physicochemical properties and digestibility of starch as revealed by logarithm of slop plot

Abstract

Interaction of pectin with starch modified by heat-moisture treatment (HMT) was evaluated. HMT preserved the presence of starch fractions with k1 and k2 (digestion rate constants at rapid and slow phase, respectively) being 4.5 and 0.42 × 10−2 min−1. Compared to the native starch, HMT starch had lower k1 and k2 probably due to the change in crystalline type. HMT increased total digestible starch from 1.02% in native to 27.23% in HMT starch. The decrease in k1 and/or k2 with the increase in pectin might be linked to the effect of viscosity or pectin–amylase interaction, while the decrease in digestible starch at rapid phase (C1∞) could be attributed to pectin–starch interaction. Pectin affected significantly water absorption capacity, syneresis, cohesiveness and gumminess of HMT starch but did not alter those of native starch. The effect of HMT on functional, textural and pasting properties was more remarkable than the effect of pectin.