The nature of concentration of metal ions in brewing liquor have long been recognised as important determinants of final beer flavour. In relation to brewing yeast and fermentation, most interest to date has focused on the roles of zinc and calcium ions in influencing wort attenuation and yeast flocculation, respectively. Until relatively recently, little attention has been paid to the role of magnesium ions in brewing yeast physiology and fermentation performance. Magnesium is absolutely essential for yeast growth and metabolism, and the bioavailability of this cation in malt wort is now recognised as being very important for efficient brewing fermentations. This paper reviews recent work which has revealed key roles for magnesium in dictating fermentative metabolism of brewing strains of Saccharomyces cerevisiae and in governing the response of brewing yeasts to environmental stress. Specifically, evidence is presented which indicates that brewer’s wort, and brewer’s yeast, may not be fully optimised with respect to magnesium status for efficient fermentative conversion of wort sugars to ethanol. Results also show that by elevating intra- and extracellular magnesium ion concentrations, physiological stress protection may be conferred on yeast cells exposed to temperature shock or ethanol toxicity. These and other findings discussed are deemed especially pertinent to high gravity brewing fermentation practices. It is hypothesised that magnesium acts at two levels when stimulating yeast fermentation performance: at the biochemical level to stimulate the activity of glycolytic enzymes; and at the biophysical level to maintain and protect the structural integrity of the yeast membrane.
|Title of host publication||Brewing yeast fermentation performance|
|Editors||K. A. Smart|
|Number of pages||6|
|Publication status||Published - 19 Sep 2000|