Effects of enzymatic hydrolysis, ball milling, and extrusion on the physical and functional properties of dietary fibers from sweet potatoes

Sweet potato pulp is a by-product of sweet potato processing with a relatively high content of dietary fiber. However, due to its less-explored functional properties, its development and utilization rate are very low. In this paper, non-fiber components in raw sweet potato dietary fiber were first removed. Subsequently, cellulase treatment, ball milling and extrusion were employed to modify it respectively. The results showed that all properties were significantly improved after removing non-fiber components. On the basis of removing non-fiber components, three groups of samples with cellulase treatment, 0 min ball milling and extrusion at 140 °C could significantly improve the water holding capacity (WHC) and oil holding capacity (OHC) of the samples. The highest WHC could reach 7.21 g/g, 7.52 g/g, and 6.88 g/g respectively, while 5.20 g/g, 5.21 g/g, and 5.61 g/g for OHC. The sample with 0 min ball milling had the highest swelling power, up to 5.40 mL/g. Extrusion at 140 °C could increase the water solubility index, glucose adsorption capacity, and cholesterol adsorption capacity of the sample to the highest, reaching 40.33 %, 44.15 mmol/g, and 26.54 mg/g (pH 7). This study provides a theoretical and experimental basis for improving the processing and functional performance of crude sweet potato dietary fiber.