EFFECT OF BLENDING RATIO AND NATURAL FERMENTATION TIME ON THE QUALITIES OF INJERA PREPARED FROM QUALITY PROTEIN MAIZE AND TEFF FLOURS

Abstract

Injera is a fermented, leavened and pancake-like bread consumed as a staple food in Ethiopia and made from cereals like teff, sorghum, wheat, maize or a combination of some of these cereals. This study was conducted to investigate the effect of blending ratio and natural fermentation time on injera qualities prepared from QPM and teff flours. A factorial design of two factors in completely randomized design arrangement was used. The factors were blending ratio of teff flour (20, 30, and 40%) and natural fermentation time (48, 60 and 72 hrs). The proximate compositions, mineral contents, sensory acceptability, firmness and microbial qualities of injera samples were analyzed following the standard procedures. The result of the study revealed that, blending ratio of teff flour and natural fermentation time had significant effect (P<0.05) on QPM-teff composite injera qualities. The interactions of blending ratio and natural fermentation time also had significant influence (P<0.05) on QPM-teff blended injera qualities. The moisture, crude protein, crude fat, crude fiber, total ash, utilizable CHO and gross energy contents of injera samples ranged from 60.63 – 62.08%, 11.86 – 13.30%, 2.80 – 3.53%, 2.19 – 3.19%, 1.46 – 1.70%, 79.02 – 80.96% and 394.46 – 403.09 kcal/100 g due to blending ratio, and from 61.12 – 61.37%, 11.93 – 13.03%, 3.03 – 3.20%, 2.74 – 2.81%, 1.55 – 1.61%, 79.66 – 80.46% and 397.99 – 398.34 kcal/100 g due to natural fermentation times, respectively. The mineral contents of injera sample ranged from 4.61 – 8.99 mg/100 g (iron), 3.03 – 3.23 mg/100 g (zinc) and 70.19 – 90.82 mg/100 g (calcium) due to blending ratio and from 6.81 – 7.32 mg/100 g (iron), 3.03 – 3.20 mg/100 g (zinc) and 78.44 – 82.83 mg/100 g (calcium) due to natural fermentation times, respectively. Increasing the blending proportions of teff flour in the composites were found improving the sensory acceptability, firmness and number of eyes of injera samples. QPM-teff composite injera samples fermented for 60 hrs also obtained better degree of liking. Significant effects (P<0.05) were also observed on yeast-mold and total aerobic plate counts of injera samples due to blending ratio and natural fermentation time. The study concluded that increasing the teff proportions in the composites were found improving the qualities of QPM-teff blended injera, since teff is expensive mixing up to 30% is recommendable. It was also suggested to use 60 hrs natural fermentation time for preparing acceptable QPM-teff composite injera