Effects of Blending Ratio and Lupine Variety on the Functional Properties of Composite Flours and Sensory Evaluations of Tef-Lupine Injera

Abstract

This study was conducted to investigate the effect of lupine flour on functional properties and sensory acceptability of tef-lupine blended injera. Injera is a staple food for Ethiopian and it is fermented, sour leavened pancake-like bread made from blending of different cereals like tef, barley, sorghum, maize and wheat. Besides, there are limited studies on formulating of injera from composite flour with legumes (lupine). The effect of two factors two lupine varieties (Australian sweet lupine and Dibettered lupine seed) and blending ratios (0, 2.5, 5, 7.5, 10, 15, 17.5 and 20). Maximum and minimum levels of independent variables were first investigated by doing a preliminary analysis and founded that tef from up to80-100% and lupines from up to 0-20%. Response surface methodology was applied to find the formulations and predictive model. Sensory acceptance of tef-lupine injera was affected by interaction of varieties and blending ratios. Oil absorption capacity and swelling power properties of composite flour decrease as blending ratio of lupines increased and water absorption and foaming capacity increased as blending ratio of lupines increases for both varieties. As the sensory acceptability scores data indicated for both lupine varieties blended with tef for the production of injeras of up to 15% lupines almost all sensory attributes showed higher scores without significantly different among them but after 15% lupine addition there were observed drop of the sensory acceptability scores. In a 7 point hedonic scale, the composite sample tef injeras with 10% dibettered lupine seed variety addition had the highest scores of 6.09, 6.22, 6.09 and 6.18 in eye size, aroma, rollability and overall acceptability respectively. The L* value and number of eye by injera eye software were 72.77 to 79.84 and 14220.43 to 18929.33, respectively. The L values of blended injera increased as lupine proportion were increased, but the number of injeras eyes decreased. yellowness (b) colour of the product. This effect was expected because of the more intense yellow colour of lupine flour. These results agree with those obtained by Dodok et al . (1993), who observed that Lupine seeds contain high levels of carotenoids and zeaxanthin which give the cotyledon (kernel) bright yellow colour and triggered the change in the yellowish colour of bread produced from a composite flour of wheat and lupine.