Optimization and characterization of wheat bran modified by in situ enhanced CO2 blasting extrusion

An in situ enhanced CO2 blasting extrusion was applied to increase soluble dietary fiber (SDF) in wheat bran. Wheat bran was mixed with a CO2-producing reagent prior to extrusion. The total addition of two reagents was 30 g/100 g with a NaHCO3/C6H8O7 ratio of 1:1 (w/w). With the aid of response surface methodology, the maximum SDF fraction in the blasting extrudate (11.64 g/100 g) could be obtained when the feed contained 24 g/100 g moisture and the extrusion was operated with barrel temperatures of 65, 105, 135, and 185 °C and screw speed at 192 rpm. This was significantly greater than that in the untreated wheat bran (2.54 g/100 g) and the reference extrudate without reagents (4.37 g/100 g). Monosaccharide analysis indicated that the increase of SDF was mainly resulted from the redistribution of insoluble dietary fiber to SDF. In addition, the blasting extrudate presented highly improved hydrating properties.