Comparative Microbiological and Physico-Chemical Properties of Commercially available Baker's Yeast and Fruit Juice Isolate (FJ1)

Seven commercially available Baker's yeasts formulations were procured from local market and stored under the conditions mentioned by the manufacturer. Microbiological analysis of the product was done using five different selective media viz. Rose Bengal chloramphenicol agar for moulds, Baired Staph agar for Staphylococcus aureus, McKonkey agar for faecal coliforms, B. cereus selective agar for Bacillus cereus and Salmonella-Shigella agar for Salmonella. The result revealed that all the commercial products differ w.r.t. to the presence of contaminants. The level of contaminants in some of the samples was above the safe limit. These contaminants may cause a substantial loss economically in the bakery industry and may also cause health problems due to the production of cytotoxic substances. Further these products were used for isolation of different yeast strains present in them using normal microbiological procedures and the isolates were compared w.r.t morphological (texture, colour, surface, elevation and margin), physiological (growth, pseudohyphae formation, budding and the presence of pellicle) and biochemical (sugar fermentation ability in both non-sugar dough as well as in high-sugar dough, invertase activity, carbon utilization as well as assimilation, nitrogen assimilation, carbohydrate and trehalose content) characteristics with a laboratory isolate (FJ1). Freeze tolerance of all these yeast isolate was studied upto 90 days.