The conundrum for brewers is that a high level of yeast activity generates a high level of heat and the brewing process runs. This leads to the temperature at the bottom of the vat becoming very warm. If this process drifts out of control, it can ruin the beer and kill many yeast cells (a form of heat stress.) As yeast cells die this can result in the beer tasting bitter, eventually reaching the point where it is undrinkable.
New research has a solution. Here, providing the correct level of nutrients to yeast is key to keeping the fungal cells healthy. Essentially, knowing how much food is provided to the yeast during exposure to hot temperatures is the main factor that affects whether or not yeast cells remain healthy.
This information was gathered using advanced cell counting through a technique called flow cytometry. This method deploys laser technology to continuously measure cells in a liquid. The method is powerful and it can assess hundreds of thousands of yeast cells in seconds. The method enables scientists to identify damaged yeast cells and to understand how different conditions affect their survival or trigger damage.
By varying levels of nutrients, the researchers demonstrated that damage to a population of yeast from heat can be reversed under the correct conditions. Yeast used in brewing is especially adapted to particular environments, tailored to produce certain flavors. This means that careful analysis is required to decide upon the optimal nutrients. However, once this is established, then yeast populations can be controlled and better established to survive the brewing process.
By fermentation, the yeast species Saccharomyces cerevisiae converts carbohydrates to carbon dioxide and alcohols – for thousands of years the carbon dioxide has been used in baking and the alcohol in alcoholic beverages. It is of key industrial importance.
The research was carried out at the Institute of Biological, Environmental and Rural Sciences at Aberystwyth University (Wales, U.K.) The findings have been published in the journal Environmental Microbiology. The research paper is headed “Surviving the heat: Heterogeneity of response in Saccharomyces cerevisiaeprovides insight into thermal damage to the membrane.”