Effects of carboxymethylation, hydroxypropylation and dual‐enzyme hydrolysis combination with heating on in vitro hypoglycaemic properties of coconut cake dietary fibres

Summary Effects of carboxymethylation, hydroxypropylation and dual‐enzyme hydrolysis combined with heating on in vitro hypoglycaemic properties of coconut cake dietary fibre (CCDF) were studied. Results showed that all the three modification methods could effectively improve ( P < 0.05) the glucose‐adsorption ability (GAA), glucose dialysis retardation index (GDRI), α‐glucosidase and α‐amylase inhibition activity of CCDF. The highest GAA (4.45–4.93 m m g −1 ), GDRI (85.09–86.94% m m g −1 ) and α‐glucosidase inhibition activity (16.39–19.37%) were found on CCDFs modified by hydroxypropylation and carboxymethylation, attributed to the increased soluble dietary fibre content, viscosity and water retention and swelling capacity. Moreover, CCDF treated by enzymatic hydrolysis combined with heating demonstrated the highest α‐amylase inhibition activity (53.95%), attributed to the high specific surface area, more porous surface structure and formation of fibre–amylase complex proved by fluorescence spectroscopy. These results suggest that the modified CCDFs could be used as low‐calorie functional ingredients in food or other industries.