A novel in-situ enhanced blasting extrusion technique - Extrudate analysis and optimization of processing conditions with okara

A novel in-situ enhanced extrusion with the aim to improve the solubility of dietary fiber in okara (OKP) was developed. Wet OKP was blended with a CO2-producing reagent (a mixture of NaHCO3 and C6H8O7) and subjected to extrusion. Processing variable optimization showed that the highest SDF fraction was obtained when the feed (containing 35.50 g/100 g moisture and 35 g/100 g reagent) was extruded with barrel temperature at 50-70-110-170 degrees C and screw speed at 191 rpm, respectively. The SDF fraction of the extrudate (21.35 g/100 g) was higher than that of untreated OKP (2.30 g/100 g) and the extrudate without reagent (4.67 g/100 g). The monosaccharide composition indicated that the increase of SDF in novel extrusion was mainly reflected in the redistribution of IDF to SDF. The novel extrusion improved the water and oil holding as well as swelling capacities of OKP when compared to untreated and reference extrudates. Industrial relevance: This article provided a novel and an effective way to improve the solubility of okara dietary fiber. It focused on the feasibility of this technique by optimizing conditions and evaluating the physicochemical properties of the resulting extrudates. This method could increase the soluble fraction (g/100 g) of other rich-in-insoluble dietary fiber plant food by-products, which could be used as valuable ingredients for new functional foods. (C) 2012 Elsevier Ltd. All rights reserved.