Enzymatic conversion of date fruit fiber concentrates into a new product enriched in antioxidant soluble fiber

•Viscozyme® L was successfully applied for date fiber solubilization.•Soluble fiber increased three times with treatment at optimized conditions.•The ratio insoluble/soluble fiber changed from 19 to 2.5.•Potentially prebiotic oligosaccharides were identified in the hydrolysates.•Hydrolysis conditions influence the molecular weight of soluble fiber.

Soluble dietary fiber (SDF) has got increasing interest because of its prebiotic effects and technological applications. The enzymatic hydrolysis is an effective treatment to convert insoluble dietary fiber (IDF) into SDF. Date fiber concentrate (DFC) is a very good source of dietary fiber, but its IDF/SDF ratio is very high. In this study an enzymatic treatment has been optimized to enrich DFC in SDF: Viscozyme® L from Novozymes A/S at 2.38 mL enzyme/100 mL reaction volume, in a solid/liquid ratio 1 g/35 mL, at 55 °C during 30-60 min. In these conditions, the amount of SDF increased from 1.8-6.3 to 5.4 g/100 g, and the ratio IDF/SDF changed from 19 to 2-3. In the SDF, besides an increase in the antiradical activity, gluco-, manno-, and xylo-oligosaccharides have been identified. Their molecular weights varied in a wide range, depending of hydrolysis duration, which suggests that this enzymatic treatment could be a promising process for obtaining tailor-made prebiotic oligosaccharides.