| Abstract: | The response of e number of Saccharomyces cerevisiae (ale) and Saccharomyces uvarum (caris-bargenaia) (lager) strains to altered starting levels of magnesium and calcium in 12°P (1048 original gravity) or 20°P (1080 original gravity) wort were investigated. In general, the same trends were observed in all 6 strains, however the extent of the response to adjusted levels of magnesium and calcium were found to be strain dependent. The results indicate that an increased ratio of magnesium to calcium causes an increase in the initial fermentation rate, the rate and yield of ethanol produced and an increase in vitality at the end of fermentation, in all strains employed. Upon increasing the calcium to magnesium ratio it was found that the initial fermentation rate was decreased, resulting in an increased attenuation time in the case of the lager strains. It was also noted that increasing the calcium to magnesium ratio led to a decreased ethanol production, maltotriose uptake, and in the case of the lager strains, maltose uptake was also adversely affected under these conditions. Altering the calcium and magnesium levels had no effect on the viability of the yeast or on glycogen levels . |
