Bread making potentials of flour from taro (Colocasia esculenta L.) As a partial substitute of wheat flour

Abstract

Bread is the main food product of wheat which is widely consumed throughout the world. Nonetheless, a continuous increase in the price of wheat is raising serious concern on the economic feasibility of wheat importation by developing countries including Ethiopia. Thus, this study investigates the nutritional, anti-nutritional and phytochemical composition, functional and antioxidant properties of flours from different taro varieties to select the most suitable variety for bread making as a partial substitute of wheat flour. Wheat flour was replaced with 7.5- 30% taro (Kihaque variety) flour using mixture design and various quality attributes of composite breads were studied. Chemical composition and bread baking were determined using the AOAC and the straight-dough standard methods, respectively. Results showed that the moisture, crude- proteins, fat, fiber, and total ash, carbohydrate and gross energy contents for taro flours ranged from 5.25 to 7.84, 4.03 to 9.28, 0.160 to 1.23, 2.96 to 5.06, 5.30 to 7.14, 81.1 to 85.4 (in g/100 g) and 354 to 372 in Kcal/100 g on dry weight basis (dwb), respectively. The mineral composition of flour from taro varieties/accessions were K (1375 to 2525), P (111 to 397), Mg (269 to 209), Ca (31.7 to 120), Zn (17.0 to 62.0), Na (20.0 to 30.0), Fe (7.31 to 20.7) and Mn (0.650 to 13.2) mg/ 100 g dwb. Oxalate, phytate, and condensed tannin contents of taro varieties/accessions ranged from 24.3 to 56.7, 6.28 to 28.9 and 57.4 to 134in mg/100 g, respectively. The total phenolic, flavonoids, β-carotene and ascorbic acid contents of the varieties ranged from 39.5 to 57.8 mg gallic acid equivalents GAE / g dwb, 4.67 to 6.27 mg catechin equivalents CE/ g dwb, 10.4 to 18.5 and 11.0 to 13.0 mg/ 100 g dwb, respectively. DPPH inhibition percentages of 25.5 to 34.7% and 62.0 to 83.7% at lowest and highest concentrations, respectively and FRAP values between 122% and 188% were obtained for different taro varieties. Water absorption capacity, oil absorption capacity, water solubility index and dispersibility of the flours ranged from, 228 to 331 %, 176 to 216 g/100 g 19.2 to 24.4 g/100 g, 18.7 to 26.7 respectively. Loaf weight of breads tends to increase with increasing proportion of taro flour, while loaf volume was the highest at 15% level of substitution and the specific volume was found to be maximum for control bread. Except for moisture and protein contents, other proximate compositions and energy values of composite breads were affected by taro flour blending ratios. An increase in the proportion of taro flour in the composite has resulted in less degree of liking by the consumer panels. In general, it appears that taro flour inclusion led to slightly reduced bread sensory quality when substituted greater than 15%. Further work, however, needs to be done to explore more in-depth quality attributes of bread such as rheological and health promoting properties of bread to have a complete picture on the quality of wheat-taro composite flour bread.