OPTIMIZATION OF PROCESSING CONDITIONS FOR INJERA MANUFACTURING

Abstract

Thirty two experiments were conducted to study the effect of amount of ersho (5, 10, 15, 20 and 25ml), absit (5, 10, 15, 20 and 25ml), and water (100, 125, 150, 175 and 200 ml) per 100 g of white teff flour, fermentation temperature (20, 25, 30, 35 and 40 0C) and fermentation time (24, 30, 36, 42 and 48 h) on fermentation kinetics of white teff. Central composite Rotatable design (CCRD) with five levels of each parameter and half replicate was used for experimental design. PH and titratable acidity were determined at one hour interval during fermentation process. Curve expert professionals software trial version, which considers linear and nonlinear equations, was used for fitting the models into the normalized pH and time data. Regression analysis results showed that DR-Logistic equation of the form where y-normalized pH, x-normalized time, α, β and γ -regression coefficients gave better prediction in most of the experiments. Coefficient of determination was more than 0.98 in almost all experiments. Therefore, DR-Logistic model is recommended for fermentation kinetics of white teff. Fermentation time was predicted using the model to reach pH of 4 and 3.8 during fermentation process which was used to optimize the process. The same procedure has been followed for getting best fit model in the case of titratable acidity and time. Regression analysis results showed that MMF equation of the form 𝑌= 𝑎𝑏+𝑐𝑥𝑑𝑏+𝑥𝑑 where y=response (A*), X is independent variable (t*), a, b. c. d, constants gave better prediction in most of the experiments. Coefficients of determination was more than 0.98 in almost all experiments. Therefore, MMF model is recommended for the case of titratable acidity and time. Acidity was calculated using the equation of this model. The recommendation for teff flour fermentation for injera making are ersho 100ml, absit 50ml, water 875 ml and temperature 25℃ to obtain pH 4 of teff dough. Corresponding to this conditions, predicted fermentation time was 5.7 h.