Comparative studies of the dough raising capacity of local yeast strains isolated from different sources

Abstract

Background: Fermentation by yeast is of primary importance for its leavening function and its possible contribution to the production of desirable flavoured compounds. Objectives: This study focused on the isolation of local yeast strains from dif ferent sources: fresh pineapple juice, palm wine and orange juices and Buruku tu. Methods: Fresh pineapple juice, palm wine and orange juices and Burukutu were kept on a sterile workbench to be fermented at ambient temperature for 72 hours. Aliquots of the fermented samples were introduced into conical flasks containing yeast extract glucose peptone broth compounded for isolation and characterization. Yeast isolated from pineapple, burukutu, orange and palm wine were characterized. The morphological, cultural and biochemical charac teristics of the yeasts were identified by using API20C AUX Kit (Bio Meriux), tested for markers characteristics such as sugars fermentation ability and starch hydrolysis. Biomass of each isolate tested was used to ferment flour dough to determine their fermentative abilities. Five out of the seven yeast isolates were compared with the commercial baker yeast (control) in terms of their dough raising capacity to confirm their baking potentials. Sensory evaluation of the baked fermented dough was carried out using these parameters: texture, aroma, taste and appearance. Results: The yeasts were identified to be Saccharomyces cerevisiae, Saccha romyces exiguus, Saccharomyces kluyveri and Saccharomyces ludwigii. Cata lase and Urease were found to be identical with the baker’s yeast (Control). The results revealed that Saccharomyces cerevisiae, Saccharomyces exiguus and Saccharomyces ludwigii yeast isolates produced loaves that have sensory properties significant (p≤0.05) when comparable with baker’s yeasts common ly used in many of the bakeries. Conclusion: The findings in this study showed that it is possible to isolate a pure culture of Saccharomyces species from fermented fruits and local bever ages for use in baking instead of importing the commercial baker’s yeast that is expensive. These local isolates if used will economize our foreign reserve. Keywords: Local yeast, Baker’s yeast, Saccharomyces species, Dough raising