Effects of micronization on dietary fiber composition, physicochemical properties, phenolic compounds, and antioxidant capacity of grape pomace and its dietary fiber concentrate

In this study, the effects of micronization of grape pomace (GP) and fiber concentrate from GP (FC-GP) on dietary fiber fractions, physicochemical properties, phenolic compounds, and antioxidant capacity were evaluated. A factorial design with two independent variables (2(2)) - rotational speed and milling time - was used to determine the best milling conditions to enhance the soluble dietary fiber (SDF) content. Constituents of insoluble dietary fiber, such as cellulose and lignin, were broken down and the content decreased after milling, resulting in increased SDF content, which indicates fiber compound redistribution. Ball milling had a significant effect on reducing the particle size, as evidenced by scanning electron microscopy. Moreover, FT-IR spectra revealed changes in typical absorption bands of polysaccharides. After milling, powder solubility increased and water holding, oil and cation binding capacities decreased. Furthermore, micronization enhanced phenolic compound extraction, mainly catechin and epicatechin, and the antioxidant capacity evaluated by ARTS and ORAC assays. The results obtained indicate that micronization modifies the dietary fiber composition of GP, increasing possibilities for use as a functional ingredient in the food industry.