The making of wine was probably man's first experience with yeast because the process does not require the use of an inoculum of yeast. The concept of yeast as the microorganism that carried out the fermentation, was not developed until ∼7000 years later with the work of Pasteur (1872) and others. These early people found empirically that it was necessary only to crush the grapes or other fruit and leave the juice (called must) to ferment. The yeast cells were already on the fruit and ready to carry out the fermentation (Mortimer and Polsinelli 1999).
In addition to wine, other alcoholic beverages were developed quite early. For example, beer is made from malted barley and other cereals and requires the addition of live yeast cells to promote fermentation. Malting, which was practiced in Egypt and Babylon, dates from at least the third millennium BC. The procedure, which involves sprouting cereal seeds, leads to the conversion of starch to fermentable sugars. Katz and Maytag (1991) have recently made beer using an ancient Sumerian recipe. They state that yeast was inoculated into the original fermentations by addition of grapes and raisins. They also may have been introduced to the malt by the addition of some fermenting wine. An alternative explanation is that insects such as bees, wasps, orDrosophila landed on the malted grain and inoculated it with yeast carried on their bodies. Most distilled beverages are also made from malted grains with the fermentation being carried out by the addition of yeast cells.
An alternative explanation is that insects such as bees, wasps, orDrosophila landed on the malted grain and inoculated it with yeast carried on their bodies. Most distilled beverages are also made from malted grains with the fermentation being carried out by the addition of yeast cells. It seems likely that the yeast cells involved in these processes, until recently, were evolving during sequential transfer. In wine making, the yeast cells are present on the grapes, and later in the fermentation, for only a few weeks in the year. Attempts to find them in the vineyard either a few weeks before or soon after harvest generally have been unsuccessful (Kunkee and Amerine 1970). Recent evidence suggests that the yeast are brought to the vineyard when the grapes are nearly ripe by insects which perhaps transport them from their nests or hives (Stevic 1962; Snowdon and Cliver 1996). We have shown that these insects primarily feed on damaged berries (Mortimer and Polsinelli 1999). These damaged berries along with many intact berries are then crushed and enter the fermentation.
Credit For Content -
Genome Research - http://genome.cshlp.org/content/10/4/403.long - Evolution and Variation of the Yeast (Saccharomyces) Genome - Robert K. Mortimer