To improve the adsorption capacities and hypoglycemic properties of millet bran dietary fibre (MBDF), four methods including acrylate-grafting, carboxymethylation, heat assisted with cellulase hydrolysis, and enzymatic hydrolysis combined with acrylate-grafting were used. The results demonstrated that all carboxymethylation, acrylate-grafting, and enzymatic hydrolysis combined with acrylate-grafting improved soluble dietary fibre content, water swelling ability and α-amylase-inhibition activity of MBDF. They also increased oil, cholesterol, sodium cholate, copper ion and nitrite ion adsorption capacities of MBDF. But carboxymethylation, acrylate-grafting and enzymatic hydrolysis combined with acrylate-grafting decreased polyphenol content, glucose-binding ability and glucose dialysis retardation index of MBDF (p < 0.05). The heat assisted with cellulase hydrolysis increased soluble dietary fibre content, polyphenol content, sodium cholate-adsorption capacity, and hypoglycemic properties of MBDF including glucose-binding ability, glucose dialysis retardation index and α-amylase-inhibition activity; but reduced adsorption capacity of MBDF on cholesterol and copper ion (p < 0.05). Changes in structure of MBDF caused by these modification methods were proved by the results of scanning electron microscopy and Fourier-transformed infrared spectroscopy analysis. These results highlight potential applications of these modified MBDFs as ingredients of hypolipidemic and hypoglycemic foods, or scavenger of nitrite and copper ion.
Keywords: Acrylate grafting; Adsorption capacity; Carboxymethylation; Enzymatic hydrolysis combined with acrylate grafting; Heat assisted with cellulase hydrolysis; Hypoglycemic property; Millet bran dietary fibre.
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