New agar formulation to detect wild yeasts
(CM920) has now been specifically formulated for use in the brewing
industry for the detection of both saccharomyces and
non-saccharomyces wild yeasts, which could cause product spoilage,
in the presence of culture yeasts.
UK company Oxoid recently announced that its yeast and mould agar (CM920) has now been specifically formulated for use in the brewing industry for the detection of both saccharomyces and non-saccharomyces wild yeasts, which could cause product spoilage, in the presence of culture yeasts.
The company recommends that the yeast and mould agar be used with copper in the examination of the microbiological quality of beers in process, pitching yeasts and packaged beers, providing consistent copper binding properties and reproducibility.
The growth and detection of wild yeasts in beer and pitching yeast is complicated by the presence of culture yeast. G.T Taylor and A.S. Marsh in the Journal of the Institute of Brewing (90:134-145), described the use of MYGP and copper medium for the selective isolation of wild yeasts - the addition of copper having an inhibitory effect on culture ale and lager yeasts and thus allowing growth of any wild yeasts present.
According to a statement by Oxoid, the authors recognised that variations in the raw materials of the formulation, such as peptones, malt, yeast extract and agar, could markedly affect the performance of the medium by neutralising the inhibitory action of the copper.
The company claims to have overcome this problem of variability through the selection and formulation of raw materials to ensure high quality, reproducible results.
Oxoid yeast and mould agar has been optimised for the addition of copper, usually within the range of 50-300mg/l depending on the sensitivity of the culture yeast to copper, as recommended by the Institute of Brewing Methods of Analysis.
