Corn, potato, and wrinkled pea starches with heat–moisture treatment: Structure and digestibility

BACKGROUND AND OBJECTIVES: Starches from corn, potato, and wrinkled pea were heat treated at 100 and 120°C for 12 hr at a moisture content of 25% to produce slowly digestible starches. The effect of heat–moisture treatment (HMT) on structure and digestibility of those starches was investigated. FINDINGS: Changes in morphological aspects could be found in corn and pea starches after HMT treatment, potato starch retained its granular appearance with only some slight breakage of granules. For the HMT‐treated starches, the intensity of birefringence slightly decreased and the polarized cross also still existed. All the HMT starches showed the increasing Tₒ, Tₚ, and Tc and the decreasing enthalpy. The X‐ray diffraction pattern of potato and pea starches was shifted from B‐ or C‐type to A‐type by HMT, and corn starch changed to A + V‐ type. Compared with native starch, the relative crystallinity of starches decreased, and the degree of gelatinization of all starches was greater than that of their counterparts. After HMT, RDS and SDS contents of potato and pea starches (except corn starch) increased compared with their native counterparts, whereas RS content of all three starches was decreased. Compared with native starch, the digestibility of starches after HMT had a certain degree of increase. CONCLUSIONS: Heat–moisture treatment had different effects on the granules morphology of different starch. The HMT samples exhibited greater Tₒ, Tₚ, and Tc values than those of the native counterparts with regard to the three starch types. The crystal structure and crystal pattern were transformed to the A‐type by HMT. Corn starch was easier to gelatinize than potato starch and pea starch after HMT, which could be the lower amylose content of corn starch and a smaller proportion of long chain. With the increase of HMT temperature, the starch sample RDS and SDS contents increased and RS decreased. SIGNIFICANCE AND NOVELTY: Corn starch was easier to gelatinize than potato starch and pea starch after HMT. With the increase in HMT temperature, the starch sample RDS and SDS contents increased and RS decreased.