MEDIA FOR YEASTS AND MOLDS

Prepoured agar plates in plastic bags 2 weeks (longer if ordered directly from supplier companies) 

Agar in botdes or screw-capped flasks 3 months 

Agar or broth in loose-capped tubes 1 week 

Agar or broth in tight-capped tubes 3 months 

Adapted from Clesceri et al. (1989) with the kind permission of the American Public Health Association. 

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WL nutrient broths and agars (Anonymous, 1984) represent general cultivation media for yeasts and molds including non-Saccharomyces yeasts, Saccharomyces, Zygosaccharomyces, and Brettanomyces. In fact, these media can be used to monitor yeast population diversity during fermentation due to unique colony morphologies of various wine yeasts (Pallman et al., 2001). Various colony morphologies are described in Section 15.2. 

Before meaningful identification work can begin, it is necessary to collect the suspect yeast into a pure culture. General growth media for yeast include nutrient, grape juice, wort, malt, and yeast and mold (YM) extract agar. With the exception of grape juice, these are commercially avail-... 

Numerous media are used for the isolation, detection, and/or enumeration of yeasts from grape juices and wines. Wort medium is non-selective for yeast and is commonly used to enumerate Saccharomyces (King and Beelman, 1986). An incubation period of 2 to 4 days at 22°G/72°F to 25°C/77°F is needed for colonies to appear. Similarly, grape juice agar is non-selective and will support the growth of many yeasts, bacteria, and molds. 

AN EVALUATION OF FOUR MYCOLOGICAL MEDIA FOR ENUMERATION OF MOLD AMD YEAST IN GRAINS AND SEEDS... 

Beuchat and Nail (1985) evaluated different media (PDA, DRBC, and PCA) for enumerating yeasts and molds in fruit purees. Overall, OGY and PDA media appeared to perform best in enumerating total yeasts and molds in those samples with high numbers of yeasts, whereas PDA was the best test medium for recovering yeasts, and PCA appeared to be less suitable for yeast production. 

Beuchat, L.R. and Nail, B.V. (1985). Evaluation of media for enumerating yeast and molds in fresh and frozen fruit purees. Food Prot. 48, 312-315. 

Yeast, bacteria, and molds all require minimal levels of moisture for growth. In general, most wine-borne yeast and bacteria need more moisture than molds. During solidification of cultivation media, agar binds water and lowers free moisture (a, ) or water activity. As such, it is important to adhere closely to the supplier s recommendations regarding the amounts of agar to include in formulations because a could be reduced too far to support growth. 

Chlorocresol is used as an antimicrobial preservative in cosmetics and pharmaceutical formulations. It is generally used in concentrations up to 0.2% in a variety of preparations except those intended for oral administration or that contact mucous membrane. Chlorocresol is effective against bacteria, spores, molds, and yeasts it is most active in acidic media. Preservative efficacy may be reduced in the presence of some other excipients, particularly nonionic surfactants, see Sections 10 and 12. 

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