Suitability of Dimensional, Physical and Physicochemical Properties of Selected Eight Improved Rice (oryza sativa l.) Varieties for Extrusion Cooking

Abstract

This research work characterized and screened local rice varieties in order to select the most suitable variety for production of ready-to-eat breakfast meals through extrusion cooking. Eight improved FARO 61-67 paddy rice varieties were milled, characterised and screened for extrusion properties. The milling characteristics, axial dimensional, physical, physicochemical, functional and cooking properties of the varieties were studied. The yield for brown rice ranged from 78.16-79.91% while head brown rice yield ranged from 23.82-75.61%. The bran yield after milling for 60 s ranged from 1.98-7.22%, while degree of milling ranged from 2.52-9.04. Length, width, and thickness for all varieties ranged from 6.21- 6.91 mm, 2.02-2.46 mm, and 1.55-1.82 mm, respectively. Length-breadth ratio, aspect ratio and kernel volume of milled rice ranged between 2.59-3.33, 0.30-0.39 and 10.72-15.97 mm³, respectively. The thousand kernel weight has range of 16.55-20.66 g, while bulk density ranged from 0.567-0.652 kgm³. Gelatinization temperature has three categories of high alkaline digestion value 6-7 (55-69 ℃), intermediate 4-5 (70-74 ℃) and low 2-3 (75-79 ℃). Cooking time was from 12.67-30.67 min while the gel consistency ranged from 33.22-37.99 mm. Total starch and amylose concentration ranged from 66.83-82.43%, and 22.21-25.96, respectively. Water absorption capacity ranged from 5.61-6.71, and length-wise expansion ratio, breadth-wise expansion ratio, and cooked length-breadth ratio ranged from 1.23-1.47, 1.38-1.50 and 2.43-2.66. Results of physical, physicochemical l, functional, cooking, and expansion characteristics of milled rice show FARO 64 variety has optimum extrusion properties. It is therefore considered the most suitable for use in rice extrusion process.