Antioxidant activity, free gamma-aminobutyric acid content, selected physical properties and consumer acceptance of germinated brown rice extrudates as affected by extrusion process

•Germinated brown rice flour (GBRF) contains gamma-aminobutyric acid (GABA).•Extrusion condition influences the extrudate quality made from GBRF.•Higher feed moisture & lower screw speed retained more GABA in extrudates.•Lower feed moisture & higher screw speed retained more phenolic content in extrudates.•The optimal extrusion condition was 16-19% feed moisture and 300-320 rpm screw speed.

Effects of feed moisture (14, 18, and 22 g/100 g) and screw speed (300, 350 and 400 rpm) on selected physical properties, gamma-aminobutyric-acid (GABA) content, antioxidant activity and consumer acceptance of extruded snacks from germinated brown rice flour (GBRF) were investigated. Changes in feed moisture significantly affected physical properties of extrudates whereas screw speed showed less effects. Decreasing feed moisture caused a decrease in bulk density and hardness, but an increase in expansion ratio. Decreasing feed moisture increased destruction of free GABA in extrudates. DPPH radical-scavenging activities, ferric reducing antioxidant power and total phenolic content of extrudates were significantly lower than those of the non-extruded GBRF. The predicted optimum extrusion condition (16-19 g/100 g feed moisture; 300-320 rpm screw speed) would yield extrudates with 25-30 mg/100 g extrudate (dry-basis) free GABA content and an overall liking score of 6.0 (on a 9-points hedonic scale).