EFFECTS OF BLENDING RATIO AND FERMENTATION TIME ON PHYSICOCHEMICAL AND SENSORY ACCEPTABILITY OF TEFF TARO COMPOSITE FLOUR INJERA

Abstract

This study was conducted on some engineering properties of taro (Colocasia esculenta) flour and its blending effect on quality of teff-taro composite injera. The experiment was planned full factorial design with two factors; blending ratios and fermentation times. Twelve combinations of treatments were executed. Taro blending ratios were 10, 20 and 30% while fermentation times were 24, 48 and 72 hours. Physical properties of taro flour were recorded to be 6.67% (db) moisture content, 41.01o angle of repose and 0.74 g/mL bulk density. The color values of taro flour were determined to be L= 80.41, a*=6.49 and b* = 18.82. The particle size distribution of taro flour showed that 71.30% was of 53 μm. The value of functional properties of taro flours, which included water and oil absorption capacities, swelling power, dispersibility and water solubility index were 1.34 g/g, 1.45 mL/g, 3.79% , 61.33% and 13.95%, respectively. The pasting properties of the flour were pasting temperature (74.29oC), peak viscosity (1025.67 cP), trough viscosity (806.66 cP), final viscosity (1904.33 cP), breakdown viscosity (221.33 cP) and setback viscosity (1095.00 cP). The proximate composition of injeras were 6.50-8.80% moisture, 10.64-13.02% crude protein, 2.14-2.44% crude fat, 1.39-1.51% crude fiber, 3.08-3.24% total ash, 71.11-76.35% utilizable carbohydrate and 358.54-366.13 Kcal/100g of energy content showing significant (p<0.05) differences due to blending ratio. Blending ratio had significant (P<0.05) effect on iron (17.31-22.10 mg/100g), calcium (139.05-142.42 mg/100g), zinc (10.46-14.17 mg/100g), beta carotein (3.14-5.83), condensed tannin (2.96-4.02) and phytic acid (106.05-112.26 mg/100g) of teff-taro injera. From the blended product, B1t3 (90% teff flour blended with 10% taro flour and fermented for 72 hours) was the best selected combined product in all sensory attributes and nutritionally because the nutritional content and anti-nutritional contents were improved with only slight effect on acceptability.