Physico-Chemical Properties and Anti-nutrient Contents of Unripe Banana and African Yam Bean Flour Blends

Abstract

This study was carried out to determine the effect of substituting unripe banana (Musa spp.) flour with different levels of African yam bean (Sphenostylis stenocarpa) flour on the proximate composition, minerals, anti-nutrients and functional properties of the flour blends. Underutilized unripe banana cultivar (“mboro ukom”) and African yam bean seeds (black variety) were separately processed into flours. The banana flour was supplemented with African yam bean flour at substitution levels of 0, 10, 20, 30, 40 and 50% to obtain the flour blends with 100% banana flour as the control sample. The results showed that substituting unripe banana flour with levels of African yam bean flour significantly (p<0.05) increased the crude protein content from 4.39% for 100% banana flour to 14.05% for 50% yam bean flour substitution while the carbohydrate content decreased significantly (p<0.05) from 90.92% for 100% banana flour to 80.12% for 50% yam bean flour substitution. The fat, ash and crude fibre contents increased with increase in African yam bean flour substitution from 0.58%, 2.80% and 1.31% for 100% banana flour to 0.98%, 3.06% and 1.79% for 50% African yam bean flour substitution, respectively. The 100% banana flour had the highest caloric value (386.46kcal/100g) while blend containing 50% African yam bean flour had the least value (385.84kcal/100g). The K, Ca and Mg decreased from 382.41mg/100g, 12.18mg/100g and 41.62mg/100g in the 100% banana flour to 345.96mg/100g, 8.93mg/100g and 33.12mg/100g in the 50% African yam bean flour blend, respectively. Conversely, the Na, Fe and Zn increased from 1.60mg/100g, 0.89mg/100g and 0.63mg/100g in 100% banana flour to 2.29mg/100g, 3.05mg/100g and 2.21mg/100g in the 50% African yam bean flour substituted blend, respectively. Oxalate, tannin, phytate and hydrogen cyanide contents increased with increase in African yam bean flour substitution. However, their values in the blended flours were low and would pose no threat to health. Blended flours exhibited higher water absorption, oil absorption, swelling and foaming capacities than the 100% banana flour. On the other hand, the bulk density decreased with African yam bean flour substitution. The study demonstrated that the nutritional quality and functional properties of unripe banana flour can be improved through supplementation with African yam bean flour.