A NOVEL AND PRACTICAL YEAST VITALITY METHOD BASED ON MAGNESIUM ION RELEASE

Using a commercial lager brewing yeast, the immediate release of magnesium, potassium and phosphate ions by cells when inoculated into wort was evaluated to be directly related to its subsequent fermentation performance. Yeast which released appreciable amounts of these ions immediately after inoculation mediated improved fermentations as evidenced by better growth, higher ethanol concentrations and lower diacetyl levels at the end of fermentation. Conversely, yeast that absorbed these ions or released them at very low concentrations performed poorly throughout fermentation producing beers with lower ethanol concentrations and higher diacetyl levels. These observations led to the identification and development of a rapid, practical and highly sensitive method to measure Mg ++ released or absorbed by yeast as an indicator of its vitality and a predictor of its subsequent fermentative performance. Full method details of the Magnesium Release Test (MRT) are given.