Study On Physicochemical Properties And Nutrient Components Of Extruded Rice Bran With CO₂ Gas Injection

Rice bran,a mixture of seed coat,outer endosperm and aleurone layers,is produced when brown rice is ground into white rice.The latest research shows that rice bran contains 64%of rice nutrients;riches in protein,fat,dietary fiber,polysaccharides,vitamins,minerals.The objective of this study was to investigate the effects of extrusion process variables and their interaction on physiochemical properties and nutritional compositions of extruded rice bran with CO2 injection.A twin-screw extruder was used.The extrusion variables were set as follow:barrel temperature(80,90,110,and 140?);screw speed(200 and 300 rpm);with CO2 injection and without CO2 injection.The results indicated barrel temperature was the most significant factor affecting expansion ratio.In addition,screw speed,and CO2 injection also significantly affected expansion ratio,cold extrusion can increase the diameter expansion rate of rice bran.The order of significant factors affected specific length was shown as follow:barrel temperature>with CO2 injection>interaction of barrel temperature and CO2 injection,cold extrusion can increase the specific length of rice bran.Bulk density was affected by barrel temperature,screw speed,interaction of barrel temperature with CO2 injection,and CO2 injection.Barrel temperature was also the most significant affecting water absorption index,followed by screw speed,CO2 injection,cold extrusion can increase the water absorption index of rice bran.And also,CO2 injection was the most significant factor for breaking strength,water solubility index,and lipoxygenase activity,cold extrusion can reduce the lipoxygenase activity of rice bran.The interaction of CO2 with screw speed and the interaction of barrel temperature with CO2 injection dramatically influenced crude fat and protein content.In addition,the a-tocopherol content and amino acid content in extrudate with CO2 injection slightly decreased.However,CO2 injection did not show significant effect on crude fat and protein content,soluble-dietary fibre content,and insoluble-dietary fibre content.Therefore,cold extrusion can increase the puffing properties of rice bran,but it is not effective in protecting nutrients.