Effect of Heat-moisture Treatment on Properties and Structure of A- and B-crystalline Type Starches

Abstract

This study aimed to assess whether there are any differences between the impact of heat-moisture treatment (HMT) on hysicochemical properties and structure of A- and B-crystalline type starches. Two kinds of A-type (rice and cassava) and B-type (canna and lasser yam) starches with a moisture content of 25% were subject to HMT at 100 ºC for 16 h. Granule morphologies of both A- and B-type starches remained unchanged after HMT. All HMT starches had lower paste viscosity and higher pasting temperature compared to the native starch counterparts. The magnitude of change was more pronounced in B-type starches. Among the same crystalline type starches, some differences in the magnitude of change could be observed, i.e., rice starch displayed a larger change than cassava starch and canna starch displayed a larger  change than lasser yam starch. X-ray diffraction pattern of the A-type starches was unaffected by HMT, whereas B-type starches was altered to C-type (B+A). Distribution profiles of debranched amylopectin as analyzed by high pressure size exclusion chromatography showed that the average chain length and unit chain distribution of the HMT starches were not significantly different from those of the native starches. The results obtained from this study lead to the conclusion that crystalline structure is a factor that significantly impacts the properties of HMT starches.