Evaluating the potential of pureed fresh green mature bananas as a functional ingredient for production of bread

Abstract

The nutritional value of green mature cooking bananas is mainly attributed to their resistant starch and dietary fibre content. This study aimed at developing bread using a composite mixture of wheat (70%) and pureed fresh green mature cooking bananas (30%) purposely to enhance its health benefits attributable to improved resistant starch and dietary fibre content, and to reduce postharvest banana losses which currently stand at 40% in Uganda. Eight treatments of wheat-banana composite bread were formulated as: (1) pureed fresh whole Mpologoma fingers, (2) pureed fresh Mpologoma pulp, (3) whole Mpologoma flour, (4) Mpologoma pulp flour, (5) pureed fresh whole N23 fingers, (6) pureed fresh N23 pulp, (7) whole N23 flour and (8) N23 pulp flour. Bread made from 100% wheat was used as the control. Alveograph and consistograph properties for each of the composite doughs were determined. Resultant bread was baked using the straight dough method, and analysed for physical attributes, as well as moisture, resistant starch and dietary fibre content using standard methods. All bread samples were assessed for sensory acceptability on a 9-point hedonic scale using 30 untrained panellists. The effect of addition of different forms (pureed fresh vs flour) and varieties of bananas on dough rheology and bread quality characteristics was evaluated by principal component analysis using XLSTAT software. Addition of pureed fresh and/or powdered bananas increased the mixing time required to reach maximum dough consistency. Mpologoma variety mostly increased the water absorption capacity of the composite mixture in pureed fresh and flour forms compared with other treatments, as it increased the amount of water needed for optimum dough production. Addition of bananas to wheat flour also reduced resistance to deformation (prmax) resulting in poor dough handling behaviour and low dough tolerance in the fermentation stage. Whereas all composite doughs generally had poor alveograph profiles suggesting low potential for using bananas in bread production, Mpologoma pureed fresh whole fingers had better rheological properties than all other composite samples highlighting its potential for application in the bread making process up to a (30%) substitution level. Additionally, dough samples containing bananas exhibited lower baking strength and resistance to mechanical mixing compared to the control indicating that the former were weaker doughs. The general appearance of bread obtained from banana-wheat composite doughs was appealing and comparable to that of the wheat alone control. High-quality bread was obtained from each of the treatments including pureed fresh or flour, whole fingers or pulp and different varieties which was contrary to alveographic and consistographic prediction data. Loaf volume ranged from 1137.97 cm3 to 14 10.00 cm3 in samples formulated from 30% N23 pureed fresh pulp and 30% N23 pureed fresh whole fingers, respectively. There was general increase in baking loss for bread formulated with banana flour compared with that made using pureed fresh bananas. Bread samples containing 30% Mpologoma pureed fresh pulp had the highest cross-sectional area while that from 30% N23 hybrid whole finger flour had the lowest. Loaf weight was highest in the 30% Mpologoma pulp flour (613.50 g), and lowest in the sample containing 30% N23 whole finger flour (544.00g). Crust and crumb browning increased with the addition of 30% bananas in comparison to the control. Composite bread exhibited reduced hardness, cohesiveness and adhesiveness compared to the control. Bread formulated using Mpologoma had highest moisture content while that made using N23 hybrid had the lowest. Overall, Mpologoma variety had higher contribution to resistant starch of the bread than the N23 hybrid, irrespective of pureed fresh or flour forms. Bread formulated from whole bananas had higher dietary fibre content than that made from banana pulp. Mpologoma whole fingers had the highest contribution to dietary fibre content of bread compared to all other treatments. Addition of bananas caused significant decrease in the sensory quality attributes of the composite breads compared to the control. Interestingly, bread made from 50% pureed fresh Mpologoma whole fingers was more appreciated for its general appearance close to that of the control. The blend of 30% Mpologoma pulp flour was most appreciated for colour. Bread texture generally hardened whereas flavour and taste decreased with the addition of bananas. It was therefore concluded that Mpologoma and N23 bananas could be added at a rate of 30-50% in pureed fresh or flour forms to formulate bread with high resistant starch and dietary fibre content. Addition of 30% banana pulp flour produced the best composite bread in terms of taste and flavour, irrespective of variety, and could have better prospects for commercial application compared with other treatments.