Physicochemical, rheological, morphological, and in vitro digestibility properties of cross-linked starch from pearl millet cultivars

The effect of epichlorohydrin (0.5%) as a cross-linking agent on physicochemical, rheological, morphological, and in vitro digestion properties of pearl millet starches from different cultivars was studied. Degree of cross-linking (DC) ranged between 40.61% and 89.75%, lower values of DC were observed for cv.HC-10 and cv.HHB-67whereas higher values were observed for cv.HHB-223 and cv.GHB-732. Cross-linked starch from cv.GHB-732 showed the lowest amylose content, swelling power, and solubility as compared to other cultivars. Rheological properties of starches during heating showed their elastic behaviour. G value was much higher than the G value at all frequency values for starch pastes. Plots of shear stress (sigma) versus shear rate (.) data for cross-linked starch pastes were fitted to Herschel-Bulkley model and yield stress (sigma(o)), flow behaviour index (n), and consistency index (K) were evaluated. Scanning electron micrographs (SEM) investigations revealed that cross-linked starch granules had slightly rough surfaceand grooves with slight fragmentations. Readily digestible starch (RDS) of cross-linked starches varied from 46.1% to 50.6%, cv.GHB-732 had the lowest value. Slowly digestible starch (SDS) and resistant starch (RS) content of cross-linked starches ranged from 34.5% to 36.4% and 13.6% to 19.4%, respectively. cv.HC-10 had the highest value for SDS content while the highest RS content was observed for cv.GHB-732. In comparison to native starches, cross-linked modification decreased SDS and RDS content whereas RS content was increased.