Growth Response of an Osmotolerant, Sorbate-Resistant Saccharomyces rouxii Strain: Evaluation of Plating Media

Abstract

Standard Potato Dextrose Agar (PDA) was inferior to PDA/60% sucrose plating medium for enumerating osmotolerant yeasts from a high-sugar food product. The largest disparity in the number of Saccharomyces rouxii cells (>2.00 log number cells/g) recovery by PDA/60% sucrose and standard PDA was during the lag and early log phase. The optimum growth temperatures of S. rouxii propagated in double strength (2X) Potato Dextrose Broth (PDB) were 28°C at 0.995 aw level and 35°C for 0.92 and 0.90 aw levels. No significant (P>0.05) difference was determined between shaking and stomaching for enumeration of S. rouxii, an osmotolerant yeast, from chocolate syrup. Therefore, use of PDA/60% sucrose incubated at 35°C for 5 d is recommended for enumeration of osmotolerant yeasts from a liquid high-sugar product.

Comparison of media performances for the recovery of some yeasts from grape juice

“…For this reason, the concentration of peptone was reduced to 0.1% and MYG0.1%P medium was also included in the study. In PDA50SG, originally given as PDA60S (Restaino et al, 1985), sucrose concentration was decreased from 60% to 40% and glucose concentration was increased from 2% to 10% (w/w).…”