Physical modification of starch: changes in glycemic index, starch fractions, physicochemical and functional properties of heat-moisture treated buckwheat starch

Native buckwheat starch was extracted and modified by heat-moisture treatment (HMT) with different treatment time (15, 30 and 45 min) to investigate its effect on physicochemical, morphological, functional properties, starch profile (rapidly digestible starch, RDS; slowly digestible starch, SDS and resistant starch, RS fractions) and expected glycemic index (eGI). Results revealed that with increasing time duration of HMT from 15 to 45 min, amylose content, pasting temperature and thermostability increased substantially whereas swelling power, solubility and viscosity parameters decreased. The SEM micrographs showed that HMT caused fissures in the granule and surface indentation. HMT-45 (starch treated for 45 min) had the lowest RDS content (29.33%) and the highest SDS (51.30%) and RS (8.21%) levels. The decreased hydrolysis rate, high amylose and RS content of HMT-45 resulted in a significant decrease in estimated glycemic index (eGI) values from 51.49% (Native) to 44.16% (HMT-45) thus indicating its role in prevention of non-insulin- dependent diabetes.