Effects of Enzymolysis Combined with Chemical Modification on Physicochemical Properties and Hypoglycemic Activity of Oil Palm Kernel Expeller Dietary Fiber

This study investigated the effects of enzymolysis combined with carboxymethylation or acetylation modification on the chemical composition, structure, physicochemical properties, and hypoglycemic activity of oil palm kernel expeller dietary fiber. The results demonstrated that both composite modification methods rendered the microstructure of oil palm kernel expeller dietary fiber more loose and porous. Fourier transform infrared (FT-IR) spectroscopy confirmed the successful introduction of carboxymethyl and acetyl groups via chemical modification, and the stretching vibration of the absorption peak around 3400 cm−1 indicated that the composite modifications disrupted the hydrogen bonds in the fiber. After enzymolysis combined with carboxymethylation and enzymolysis combined with acetylation, the soluble dietary fiber content of oil palm kernel expeller fiber increased significantly from 4.00% to 16.14% and 12.85% (P<0.05); water-holding capacity rose from 2.06 g/g to 5.72 g/g and 4.15 g/g; water-swelling capacity increased from 1.01 mL/g to 3.58 mL/g and 2.46 mL/g; viscosity increased from 4.08 cP to 13.90 cP and 7.71 cP; glucose adsorption capacity enhanced from 1.84 μmol/g to 3.99 μmol/g and 4.53 μmol/g; and glucose diffusion inhibition capacity improved from 16.32% to 38.18% and 25.15%, respectively. In addition, for the oil palm kernel expeller dietary fiber treated with enzymolysis combined with carboxymethylation, its α-amylase inhibitory activity (19.41%) was increased by 0.43 times compared with that of the unmodified fiber, while the activity of the oil palm kernel expeller dietary fiber treated with enzymolysis combined with acetylation was not improved. In conclusion, enzymolysis combined with either carboxymethylation or acetylation could enhance the physicochemical properties and hypoglycemic activity of oil palm kernel expeller dietary fiber to a certain extent, with enzymolysis combined with carboxymethylation yielding the best results. This thus expands its application potential in the food industry.