Application of Wild Yeast (Saccharomyces cerevisiae) Isolates from Palm Wine and Honey in Baking of Cassava/Wheat Composite Bread

Abstract

Saccharomyces cerevisiae (baker’s yeast) and wheat flour are the conventional raw materials used in baking of bread. Wheat flour is preferred due to gluten proteins providing bread elasticity. Interest is shown in using flours from cassava mainly due to economic and health reasons. Cassava does not have gluten protein required for bread elasticity. A different type of yeast would be required to bake bread using cassava flour. We investigated the use of composite (cassava/wheat) flour technology for bread baking. We also isolated yeast strains from palm wine (SPW) and honey (SH) using enriched media and evaluated their ability to produce acceptable cassava/wheat composite flour bread. Total of six yeast (3 each for palm wine and honey) strains identified as Saccharomyces cerevisiae were isolated. Two strains designated SPW and SH were selected and used for bread production. A commercial yeast strain (CY) was used as control. The major interest in this study included aroma, colour, taste, crust/texture, pore size, loaf weight and volume. Yeast concentration—1% - 3%, and flour composite combinations of 90% wheat/10% cassava, 80% wheat/20% cassava, and 70% wheat/30% cassava were studied. The control was 100% wheat flour. Bread made from 90W:10C and 80W:20C compared favourably with bread made from 100% wheat flour. Loaf volumes were: SPW (850 cm3), CY (760 cm3) and SH (570 cm3), whilst loaf weights were: 243 g for SPW, 260 g for CY and 298 for SH. Pore size estimations were: SPW loaf porosity (0.765), CY (0.740) and SH (0.655). Yeast concentrations of 2.5% performed best when SPW was used to produce bread from 70W:30C composite loaf. SPW also displayed combined role of gas production, aroma and flavor development in wheat/cassava composite bread. Mean performance of CY, SH and SPW on sensory parameters of bread produced, varied significantly (p CY > SH.