(Posted:01-Jul-2015)

Yeast is used in brewing. Yeast is mixed with sugar found in food substances used in brewing.Not all yeasts are suitable for brewing. In brewing we use the sugar fungi form of yeast. These yeast cells gain energy from the conversion of the sugar into carbon dioxide and alcohol. In confined spaces the carbon dioxide dissolve in the liquid making it fiZzy.Alcohol is the other by-product of fermentation. Alcohol remains in the liquid which is great for making an alcoholic beverage but not for the yeast cells, as the yeast dies when the alcohol exceeds its tolerance level. The overall process of fermentation is to convert glucose sugar to alcohol and carbon dioxide gas. The reactions within the yeast cell which make this happen are very complex but the overall process is as follows: C6H12O6 ====> 2(CH3CH2OH) + 2(CO2) + Energy (which is stored in ATP) Sugar ====> Alcohol + Carbon dioxide gas + Energy (Glucose) (Ethyl alcohol). Note: The sugars used can be a range of fermentable sugars. These sugars are converted by enzymes to glucose which is then converted to alcohol and CO2. Some sugars are not able to be fermented and will remain in the liquid. Fermentation and yeast in brewing Brewer's yeast tolerate up to about 5% alcohol. Beyond this alcohol level the yeast cannot continue fermentation. Wine yeast on the other hand tolerates up to about 12% alcohol. The level of alcohol tolerance by yeast varies from 5% to about 21% depending on yeast strain and environmental conditions. The fermentation process has limits such as temperature. Greater than 27C kills the yeast less and than 15C results in yeast activity which is too slow.