Effects of acid hydrolysis level prior to heat-moisture treatment on properties of starches with different crystalline polymorphs

Abstract

Highly crystalline starches find applications as resistant starch because of their improved thermal stability and reduced enzyme susceptibility. Both acid hydrolysis (AH) and heat-moisture treatment (HMT) have been used to alter starch gelatinization properties and digestibility. This study investigated the effects of varying AH levels (0–9%) prior to HMT on the structures and properties of starches with different crystalline polymorphs, including the A-type corn starch, the B-type potato starch, and the C-type pea starch. HMT resulted in significant increases in gelatinization temperatures and significant decreases in gelatinization enthalpy and α-amylase digestion for all three starches. When combined AH with HMT, all three starches generally displayed increases in gelatinization temperatures, gelatinization enthalpy and relative crystallinity with increasing AH level, but the susceptibility to α-amylase varied with starch type and AH level. Acid preferentially hydrolyzed the amorphous regions involving amylose and amylopectin branch points, and increased hydrolysis levels yielded greater amounts of linear chains that were capable of reorganizing into crystallites during HMT. The greater AH level, up to 9%, combined with HMT promoted the formation of more thermally stable crystallites for starches with different crystalline polymorphs.