Potential test of endophytic yeast from sweet oranges (Citrus sinensis L.) as leavening agent for bread

Yeast is one of the most important ingredients in bread making and, it may be isolated from local fruits such as sweet oranges as a commercial yeast substitute. This research aimed to isolate yeast from sweet orange (Citrus sinensis L) that may be used as a bread improver. The method used was the endophytic yeast isolation on the rind and flesh of sweet citrus fruits. It is identified macroscopically, microscopically and analyzed for carbohydrate fermentation, growth in 50% glucose medium, hydrogen sulfide (H2S), flocculation, temperature tolerance, and ethanol, as well as the use of yeast isolates as bread dough improver. Five yeast isolates were obtained based on the results: RYB1, RYB2, RYK1, RYK2, and RSK1. All isolates had similarities with the Ascomycetes class, specifically the Hemiascomycetes subclass, as indicated by the overall asexual reproduction of yeast cells by budding. RYK2 isolate was the best bread improver, with the same dough volume as the positive control (Fermipan®) and a better aroma than the positive control. Subsequently, Isolates RYB1, RYB2, and RSK1 had a satisfactory ability to develop bread dough, unlike RYK1. Furthermore, the RYK2 isolate has the highest potential for bread development and can be a commercial yeast candidate.