We're big fans of testing beer here at Laboratorytalk, although we've never used this range of culture media for the microbiological analysis of the liquid and its raw materials
Oxoid supplies a comprehensive range of culture media for use in the microbiological analysis of beer and its raw materials, including malt, sugars (bulk and dilute), water, culture yeast and pitching yeast, wort, beers in process and final products. The quality of the final beer product depends not only on the fermentation process, but also on the quality of the raw materials used.
Microbial contamination of raw materials can lead to, among other things, premature spoilage of the beer (due to spoilage bacteria, yeasts and moulds) and gushing (caused by the presence of Fusarium spp, commonly found in barley).
The wide selection of media available from Oxoid includes WL nutrient agar (CM309) for total microbial counts (this can be made selective for bacteria with the addition of cycloheximide), Lysine medium (CM191) for the isolation and enumeration of non-saccharomyces wild yeasts (suppressing the growth of pitching yeasts), Yeast and mould agar (CM920) plus copper for the detection of both saccharomyces and non-saccharomyces wild yeasts in the presence of culture yeasts, and Raka-ray agar (CM777) which, with phenylethanol and cycloheximide, provides a selective medium for the isolation of lactic acid bacteria in beer.
Recommendations for the use of these and other media available from Oxoid are detailed in the Institute of Brewing Methods of Analysis (1997) Volume 2 under section 21 - Microbial Process Control.
