Effects of carboxymethylation, acidic treatment, hydroxypropylation and heating combined with enzymatic hydrolysis on structural and physicochemical properties of palm kernel expeller dietary fiber

Abstract

Effects of acidic treatment, hydroxypropylation, carboxymethylation and heating combined with enzymatic hydrolysis on structural and physicochemical properties of palm kernel expeller dietary fiber (PKEDF) were studied. The carboxymethylation, hydroxypropylation and heating combined with enzymatic hydrolysis effectively improved soluble dietary fiber (SDF) content, water retention capacity (WRC), emulsifying ability index (EAI), water swelling capacity (WSC), viscosity and α-amylase inhibition activity of PKEDF. The carboxymethylation also significantly (p < 0.05) increased emulsion stability index (ESI), but decreased oil retention ability (ORA) and brightness of PKEDF. Besides, the enzymatic hydrolysis with heating significantly enhanced ORA of PKEDF (p < 0.05). In contrast, the acidic treatment decreased the WRC, ORA and EAI of PKEDF. These effects were mainly attributed to the composition and structural modifications as evident from scanning electron microscopy, Fourier-transformed infrared spectroscopy and X-ray diffraction analysis. The changes in physicochemical properties of PKEDF caused by these modification methods can expand its applications in food and other industries.