Extraction of Deoiled Walnut Dietary Fibers and Effects of Particle Sizes on the Physiochemical Properties

Abstract

In this study, chemical method and enzymatic method were used to extract dietary fibers (DF) from deoiled walnut residues, and the resulting fibers were named as CDF and EDF respectively. The CDF and EDF were characterized by FTIR, XRAD and SEM. Moreover, the effects of particle sizes on physiochemical properties of CDF and EDF were explored. The results indicated that enzymatic method inhibited the structural damage of walnut DF, thus increasing the external surface area of EDF. Besides, particle sizes affected the physiochemical properties (water retention capacity (WRC), oil retention capacity (ORC), water swelling capacity (WSC) and apparent viscosity) of walnut DF. Particle sizes ranged from 180 to 450 µm, CDF and EDF had higher WRC. In the particle sizes range of 125–180 µm, CDF and EDF had higher ORC and apparent viscosity. These results might provide a reference for the utilization of walnut DF in food industry.