| Whether it has either been distilled or fermented, any | | | | therefore concentrates on survival and in doing so |
| alcoholic beverage contains the by-product of yeast | | | | produces the waste by-products of carbon dioxide |
| induced ethanol content. The majority of times it was | | | | and ethanol in the process before expiration. If the |
| added by the process of fermentation, which is the | | | | ratio of alcohol levels reach 12% and above in volume |
| metabolism of sugars already present in the liquid by | | | | to the brew, then this can inhibit activity as the |
| the 'pitching' of yeast. With regards to beer, the | | | | ethanol is toxic to the yeast. |
| addition of the brewer's yeast breaks down sugars in | | | | There are typically two different types of yeasts |
| the sweet liquid known as 'wort' or 'green beer', | | | | used in modern brewing techniques, which are known |
| producing carbon dioxide emissions necessary for | | | | as top-fermenting and bottom-fermenting yeasts. |
| natural carbonation, and alcohol necessary for | | | | Top-fermenting yeasts commonly a strain of |
| providing a merry disposition. | | | | Saccharomyces cerevisiae is so-called because they |
| Yeast cultures have been applied as an ingredient to | | | | produce thick foam at the top of the brew during |
| food recipes for thousands of years in order to | | | | the fermentation process. These yeasts produce |
| create such products as beer and bread. They are | | | | beer of a sweeter, more fruitier flavor commonly |
| known to be one of the earliest domesticated | | | | associated with ales, developing higher alcohol |
| organisms used by man in food preparation, and are | | | | concentrations, and preferring temperatures of |
| commonly found on the skin of fresh fruits as mold | | | | around 16-24°C for optimal performance. |
| just waiting to turn them into rotten mush. Yeasts | | | | Bottom-fermenting yeasts however require lower |
| are predominantly single celled micro-organisms under | | | | temperatures of around 10°C to give the best |
| the classification of fungi varying greatly in | | | | results, and are more suited towards the brewing of |
| microscopic size, and reproduce asexually in an | | | | lager beers. They are able to ferment more sugars |
| oxygen rich environment. There are around 1,500 | | | | which result in the beer having a crispier taste, and |
| species known to man, some of which harmful, but | | | | can still operate at temperatures near freezing, one |
| one of the most common species is Saccharomyces | | | | of which being known as Saccharomyces pastorianus |
| cerevisiae. This particular genus comprises of various | | | | for example. |
| different strains, some of which are aggressive in | | | | There are other strains of wild yeasts used in the |
| reproduction and are suitable towards bread-making, | | | | brewing of beer known as the species |
| while others are more placid and are ideal for brewing | | | | Brettanomyces, but these tend to work on different |
| beer. | | | | principles. Instead of being deliberately added to the |
| Yeasts live on organic compounds as a source of | | | | wort, these airborne yeasts are introduced into the |
| energy and do not require sunlight to grow. They do | | | | environment, and with the help of bacteria create |
| require oxygen to reproduce and multiply, though do | | | | spontaneous fermentation in the brew. Popular in |
| not need to live in an atmospheric environment to | | | | Belgium, these brews are known as lambic beers. |
| actually survive. They grow best under either neutral | | | | Regardless of yeast type though, one thing they do |
| pH or slightly acidic conditions, with a comfortable | | | | all have in common is that the cultures are naturally |
| growth rate in a temperature range of between | | | | distributed evenly and fully throughout the beer |
| 10-37 C, and around 30 C being the best for | | | | during the fermentation. It is only once their job is |
| reproduction. When used as an ingredient to begin | | | | done they are finally laid to rest as dead particle |
| the fermentation process to produce beer, yeast is | | | | sediment in the bottom of the brew, to either be |
| pitched in to the wort and immediately begins to | | | | filtered off before consumption, or to add character |
| break down sugars present. With the lack of oxygen | | | | to the beer at the sole choice of the brewer. |
| in the liquid the yeast finds it difficult to breed, | | | | |
