Optimisation of extrusion cooking conditions and characterization of rice (Oryza sativa)—Sweet potato (Ipomoea batatas) and rice-yam (Dioscorea alata) based RTE products

摘要

?Extrusion cooking has been extensively used toproduce variety of foods like ready to eatbreakfast cereals, baby foods, snack foods, etc. Taking rice flour as the base ingredient, two locally available tuberous root vegetables, greater yam(Dioscoreaalata) and sweet potato (Ipomoeabatatas) were used in this study for the development of ready-to-eat breakfast products in asingle screw extruder. During extrusion cooking, the screw speeds ranged from 132 to 468 rpm and the barrel temperatures ranged from 103°C to 137°C. The extrudates were then analyzed for various physical and physicochemical properties. Optimization was done following ResponseSurface Methodology (RSM) using CentralComposite Design. Using screw speed, barrel temperature and feed composition as the three independent variables, the three responses taken were bulk density, expansion index and breaking strength. The optimized conditions wereused for developing 3 new products one of which alsocontained tomato pulp powder. The productswere analyzed for their physical, proximate, sensoryand antioxidant properties. There was significantcolour change in all the three samples as indicated by total colour change (ΔE). Texture analysis of the extrudate samples showed hardness values ranging from 28.68 N to 47.57 N. Amylose content was found to be 15.3% in rice-sweet potato extrudate, 14.7% in rice-yam extrudate and 18.2% in rice-sweet potato-tomato extrudate. The antioxidant profile of the extrudates studiedthrough DPPH (2,2-diphenyl-picryhydrazyl)scavenging activity and FRAP (ferric reducing antioxidant property) showed that the antioxidant capacity in all the 3 extrudates was very low. Rice flour incorporated with sweet potato wasjudged the best on sensory evaluation. Thestudy has shown that both sweet potato and greater yam tubers can be commercially exploited for the development of ready-to-eat (RTE) products.