The use of brewing paddles ensured that yeast was carried over from batch to batch. Cold northern regions selected yeast that could ferment in colder temperatures. However, humans were able to select certain traits in yeast without being aware of the manipulation. The cause of the transformation from juice to wine or grain to beer remained a mystery for thousands of years. The solution fermented and someone drank it and liked the taste and most likely the effect. A sugar solution of some kind (exactly what the first fermented beverage consisted of is a hotly contested issue) was left out and yeast dropped into it from the air or was on the surface of the fruit or grain used to make the solution. The first fermented beverages were purely accidental. The ability to metabolize a wide range of sugars allows Saccharomyces cerevisiae adapt to many environments. Saccharomyces cerevisiae is a species that has the capability of utilizing a wide range of sugars such as, glucose, fructose, mannose, galactose, sucrose, maltose, maltotriose, and raffinose (lager yeasts can also metabolize melibiose). Basically, anywhere there is a carbohydrate (sugar) source, you will probably find yeasts that are adapted to consume it. Yeasts are everywhere! There are several hundred recognized species of yeasts, with many strains within each species classification. There are literally hundreds (if not thousands) of strains of yeast used for fermentation to create alcoholic beverages in almost every society on earth. Since that time, yeast strains have been isolated and recognized for unique characteristics that help create specific styles of beer and add specific characteristics to wine, distilled spirits, and bread. As important as yeasts are in our common history, it was not until relatively recently (1841) that yeasts were recognized as the cause of fermentation. Without yeast, important staples like bread, beer and wine would not exist. Yeasts play an important role in human history. Yeasts are very small, typically 5 to 10 microns (1 micron = 10 -4 centimeters) which is around 5 times the size of most bacteria. Ale and lager yeasts are currently both classified as Saccharomyces cerevisiae but historically have been considered separate species with lager yeasts in the Saccharomyces uvarum (carlsbergensis) classification. In brewing, Saccharomyces cerevisiae is the Genus and Species that is of the most significance. Yeasts are eucaryotic single celled fungi which reproduce by budding or fission.
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