The growth and detection of wild yeasts in beer and pitching yeast is complicated by the presence of culture yeast. Taylor and Marsh described the use of MYGP + Copper Medium for the selective isolation of wild yeasts 1 - the addition of copper having an inhibitory effect on culture ale and lager yeasts and thus allowing growth of any wild yeasts present. However 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.
Thermo Scientific has overcome this problem of variability through the careful selection and formulation of raw materials to ensure high quality, reproducible results. Thermo Scientific 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 2.
1. Taylor, G.T. and Marsh, A.S. (1984) J Inst Brew, 90:134-145
2. Institute of Brewing Methods of Analysis. (1997) Volume 2. Microbiological. 23.45