Brewing much studied, the preservative nature of the soft resins is not yet fully understood, though it has been observed that unless stored at a cool temperature, the preservative nature will decrease. Brewing is the sole major commercial use of hops. Yeast is the microorganism that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces alcohol and carbon dioxide, and thereby turns wort into beer. In addition to fermenting the beer, yeast influences the character and flavour. The dominant types of yeast used to make beer are "Saccharomyces cerevisiae", known as ale yeast, and "Saccharomyces
Alcohol congener analysis from blood samples, by targeting iso-alpha-acids-type compounds that are derived from the hops used during the brewing process. Levels of these compounds have been found in blood several hours after ingestion in controlled drinking studies using "high-" and "low-hopped" beers. This methodology presents new possibilities for accompanying-alcohol analysis as ingredient-specific markers are developed for other alcohol beverages, e.g. wine and spirits. Alcohol congener analysis Alcohol congener analysis of blood and urine is used to provide an indication of the type of alcoholic beverage consumed. The analysis involves investigating compounds called congeners that give the beverage a distinctive appearance, aroma, and