Brewery yeast culture, pitching and harvest yeast as well as pure yeast.
Thermally extracted yeasts release their cell contents into the surrounding medium (= yeast water), which is then available for bacteria.
The moisture content of barley must be determined prior to its storage.
Determination of the moisture content of barley is carried out according to ISO 712, 2009, i.e., milled barley is dried at a defined temperature within a set time period in an electrically heated air-drying oven.
The moisture content is calculated through the difference in mass prior to and after drying.
Barley with moisture contents above 17 % must be pre-dried as whole kernels prior to analysis. This method is not suitable for malt.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
For determination of the dry residue in water after filtration, a certain quantity of filtrate is evaporated until dry. It is subsequently dried in a drying oven to eliminate any remaining moisture.
Brewing yeasts
Analysis of yeasts for dead cells using propidium iodide in a cell counter.
Foreign organisms in brewery yeasts are primarily obligate beer-spoilage organisms and wild yeasts. This method aims to detect wild yeasts in brewery yeast cultures.
Process samples containing yeast
Brewery yeast cultures cannot grow in the presence of more than 200 ppm copper sulphate (CuSO4) in a culture medium. The majority of wild yeasts are not inhibited by this concentration. This means that a universal yeast medium (e.g. YM) with the addition of 200 ppm CuSO4 can help detect the presence of wild yeasts in bottom- and top-fermenting brewery yeast cultures.
Foreign organisms in industrial yeasts are primarily obligate beer-spoilage organisms (gram-positive and gram-negative anaerobes) and wild yeasts.
Brewery yeast and purchased yeast
Dark-field microscopy of the sample with subsequent enrichment.