Abstract:
Injera is a fermented and naturally leavened flatbread indigenous to Ethiopia. However,
variation in processing steps results in the difference in the quality of injera, which might even
baked from the same variety of teff. To minimize such variability it is necessary to study and develop
pre-baking and baking standard procedures that fit for industrial and export purposes. In line
with this, the research initiated to optimize pre-baking processing and baking conditions for the
better quality of teff injera. Four consecutive experiments were conducted: The first and second
phases of the study were conducted using response surface methodology with a central
composite design to optimize the effect of primary fermentation condition (time and
temperature), and absit mixing ratio, cooking time and secondary fermentation time respectively.
Optimization was made by taking primary fermentation temperature and time in the range of 25–
38℃ and 24–96hrs, absit mixing ratio of 5-15%, the cooking time of 5-15min and secondary
fermentation time of 2-6hrs. Standard methods were used to conduct physicochemical quality
analysis of injera. The result showed that primary fermentation condition and absit mixing ratio,
absit cooking time and secondary fermentation time were influenced most of physicochemical
quality parameters. Numerical optimization for these parameters were carried out by setting
criteria (minium, maximum and in the range) for dependent variables. Accordingly, the best
response variables were obtained at the optimal condition of 25℃ primary fermentation
temperature for 64 hrs fermentation time, 8% mixing ratio of absit with 10 min of cooking and 4
hrs of secondary fermentation time. The third phase of the study was conducted using
randomized complete block design with the factorial arrangement in 3 replications to evaluate
the effect of baking temperature (195±5, 215±5, 235±5 and 255±5℃) and time (1, 2 and 3
minutes) on physicochemical and sensory quality of injera. The result indicated that the
interaction effect of baking temperature and time differ significantly (P ˂ 0.05) and 255±5℃ for
2 min or 235±5℃ for 3 min out weight other treatments in terms of all physicochemical and
sensory quality evaluated. Finally, validation study was performed to evaluate the robustness of
optimized pre-baking processing steps and baking condition for five different varieties of teff
using a completely randomized block design in three replications. Results indicated that there
were insignificant differences (P > 0.05) among four teff varieties in terms of physicochemical
and sensory quality except for red teff. Therefore, the optimized pre-baking processing steps and
baking condition could be used to produce better quality of teff injera at large commercial scale
capacity to reach both local and export markets.
