EFFECTS OF COMBINATIONS OF FERMENTATION DURATION, BAKING TEMPERATURE AND BAKING TIME ON TEFF (Eragrostis teff) INJERA QUALITY ATTRIBUTES

Abstract

Injera is an Ethiopian fermented flatbread made from teff grain flour [Eragrostis teff (Zucc.) Trotter]. Injera is steam baked on a clay baking griddle. Fermentation duration, baking temperature-time combinations are factors that can affect quality attriutes of injera during baking . As a result, the goal of this study was to optimize these three parameters in order to improve the physicochemical and sensory acceptability of baked teff injera using the Box-Behnken Response Surface Methodology (RSM). Injera baking process variables and their levels studied selected were: fermentation time (24, 48, and 72 h), baking temperature (160, 180, and 200 oC), and baking time (2, 3, and 4 min), comprising 17 experimental runs with 5 center points using RSM. Angle of repose, Bulk density of teff grain and floor were evaluated with out consideration of the three factors and pH of batter was also evaluated at three level of fermentation time only. While Proximate composition, pH of injera, mineral contents (Ca, Fe and Zn), antinutritional factors (condensed tannin and phytic acid) and sensory acceptance of injera were evaluated under the three factors. The response variables were injera eyes, color, appearance, taste, injera underneath surface, texture, and overall acceptability. The overall acceptance, pH values, eyes of injera, and texture were optimized. The results show that the quadratic model fit was highly significant (P<0.0001) for eyes of injera and overall acceptability. The best sensory score (6.54) for overall acceptance was observed when the dough was fermented for 48 h. and baked at 180 oC for 3 min. The optimized pH value (3.87) was observed when the dough was fermented for 48 h and baked at 180 oC for 3.2 min. Sensory evaluation on the injera eyes (6.54) and texture (6.3) were observed for injera baked at 180 oC for 2.7 min at 60 h of fermentation time. The optimum baking factor levels for the best injera quality depending on the overall acceptability optimized were fermentation time 48 h baked at 180 oC for 3 min. Injera produced under the optimum conditions was subjected to sensory evaluation, and the results were compared with the RSM predictions