Yeast – Saccharomyces cerevisiae – For centuries this microscopic beast has provided the magic for turning sugar-rich solutions into alcoholic beverages. But not until the late 1800s did work by Louis Pasteur and others reveal the nature of that miracle goop that some had termed simply “God is good.”
This single-celled organism reproduces by budding. During the early hours of beer fermentation the population of yeast added to a fermenter multiplies several times over so that the final mass of yeast recovered from the beer is five times what was added at the beginning. During that growth, the yeast scavenge all the oxygen from the fermenter and once it is consumed, they begin the process of anaerobic fermentation wherein one molecule of sugar (glucose) is converted into 2 molecules of ethanol (beverage alcohol) and 2 molecules of carbon dioxide (CO2). But while this basic transformation is essential to yeast’s many uses, in beer yeast also produce various flavors that define the final beer. Desirable flavors include esters that contribute fruitiness to ales, and phenols that give clove flavors to German wheat beers or earthy notes to Belgian farmhouse ales. But if mistreated, the yeast may wreak revenge on the brewer by leaving behind flavors of latex paint, butterscotch or burnt matches.
And by the way, the same species puts the life in bread as well—although the strains used for brewing and baking are quite different.
This cache consists of a tube like those used to deliver live yeast to homebrewers. Just imagine being able to make 5 gallons of tasty goodness from this one little tube!