The development of Amadumbe (Colocasia esculenta (l.) schott)-soya composite biscuits with improved nutritional and sensory properties

Abstract

The Amadumbe crop [Colocasia esculenta (L.) Schott] is a traditional Southern African tuber crop which is rich in starch, mucilage and micronutrients. Amadumbe tubers have limited amount of proteins and as a result, amadumbe-processed foods lack adequate protein. The purpose of this study was therefore to develop protein-rich amadumbe-soya composite biscuits, which would be acceptable to consumers. Biscuits were prepared by combining amadumbe and soya flours at ratios: 90:10, 70:30 and 50:50. Functional properties of composite flours and the physical properties of composite biscuits were determined. The proximate composition, amino acid composition and protein digestibility of composite biscuits were determined. Consumer acceptability test of biscuits was performed using nine-point hedonic scale. The results indicated that the 90% amadumbe and 10% soya composite biscuits had high significant values of moisture, ash, carbohydrates contents and energy values. The 50% amadumbe and 50% soya composite biscuits had significantly high values of fat, crude protein contents and acid detergent fibre (ADF). The protein digestibility, amino acid contents, especially the lysine contents of composite biscuits increased significantly (p ≤ 0.05) with an increase in the percentage of soya. The mineral contents of composite biscuits; Ca, Mg, P, Zn, Cu, Mn and Fe increased significantly (p ≤ 0.05) with the increase of soya in the composite biscuits. There was a significant difference in the mean taste acceptability and mean overall acceptability when the soya concentration was increased to 50%. Soya was successfully used to produce amadumbe composite biscuits with better nutritional quality with respect to protein content, amino acid profile and selected mineral contents and which were acceptable to consumers.