OPTIMIZATION OF GLUTEN-FREE BREAD PREPARED FROM GREEN BANANA, PUMPKIN SEED AND CASSAVA COMPOSITE FLOURS

Abstract

Awareness and increased diagnosis of celiac disease and gluten intolerance in African countries has created the need for developing innovative and improved quality and gluten free breads. The locally available food products such as, green banana, pumpkin seed and cassava flours which are gluten-free and have ideal baking qualities are underutilized in commercial bread production. The main objective of this study was to formulate, develop and determine the physico-chemical and sensory properties of gluten-free bread made from green bananas, pumpkin seed and cassava composite flours. Mixture design experiment was used to formulate seven variations of bread that included 100% each of banana, pumpkin seed and cassava flours, composites with 50:50 Banana: Pumpkin seed, Banana: Cassava and Pumpkin seed: cassava, one sample with ⅓ of banana: pumpkin seed: cassava, while the eighth 100% wheat was the control. To investigate the chemical characteristics, proximate composition including moisture, protein, fat, ash carbohydrate and energy and mineral content including zinc, iron, phosphorous and copper were determined according to standard AOAC International Methods. Physical characteristic (specific volumes) were established using AACC seed displacement method. The sensory characteristics of gluten-free bread were evaluated for hardness, springiness, cohesiveness, chewiness and resilience using a descriptive panel Acceptability was evaluated by 55 consumers using a 9 point hedonic scale for appearance, smell, flavor and texture. Results for the flour were reflected in gluten-free bread blends. Compositing flours with PSF significantly increased ash by 21-50%, lipids by 69-81%, proteins by 50-90% and energy by 46-57% compared to all other breads. Green banana bread had highest (1.51 mg/100 g) phosphorus content.. Pumpkin seed bread had the highest levels of manganese, copper, zinc and iron of 0.15, 0.95, 2.52 and 2.57 mg/100 g respectively. Gluten-free breads were close to wheat bread in specific volume with a difference of 16% in overall centroid green banana pumpkin seed cassava bread and in 24% in binary combination of green banana cassava bread. . Green banana bread proved to be the hardest with 11.07 N compared to wheat bread (control) with 4.31 N. Cassava bread was only 6% and 8% less springy and cohesive respectively than wheat bread. All the gluten-free breads and wheat bread recorded the same in chewiness with a range of 2.53 to 5.52 with green banana bread on higher side. Principal Component Analysis (PCA) explained 86% of the total variation in bread samples, of which 57% separated wheat from gluten-free breads, while 29% separated bread types with pumpkin seed and those without. All the gluten-free breads were liked by consumers with scores ranging from 70-76%.Combination of pumpkin seed cassava bread was the highest ranked gluten-free bread by consumers. Optimization results for combined proximate, physical and consumer acceptability of gluten-free breads scored pumpkin seed bread at 72% with overall desirability was 89%. Pumpkin seed flour produced the most nutrient dense bread with increased levels of ash (minerals), fiber, protein and fat content. Pumpkin seed flour will serve as a vehicle in food fortification for both celiac patients and gluten sensitive individuals. The best physical characteristics are imparted by cassava flour. It is recommended that locally available food products like green banana, pumpkin seed and cassava be promoted for use in production of gluten-free bread and other baked products in Kenya and other developing countries.