Foreign organisms in bottom-fermenting industrial yeasts are primarily obligate beer-spoilage bacteria, wild and top-fermenting yeasts. This method is aimed at detecting wild yeasts and top-fermenting yeasts which grow at 37 °C.
Yeast samples (e.g. propagation yeasts, cropped yeasts) and process samples and beers that contain yeast.
Bottom-fermenting brewery yeast cultures cannot grow at a temperature of 37 °C. The majority of wild yeast species and top-fermenting brewery yeast cultures can grow at this temperature.
If bottom-fermenting yeast culture is inoculated into a universal yeast medium (e.g. wort, YPG, YGC or YM) and this is incubated at 37 °C, wild yeasts and top-fermenting brewery yeast cultures can be detected if contamination is present.