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Ingredients in Beer - Hops and Yeast |
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Page 2 of 3 Hops (humulus lupulus) are a flowering vine whose flowers are used as a preservative and for their essential oils that add flavor (bittering hops) and aroma (aroma hops) to balance the sweetness of the malt. Usually dried before use, the bitter flavor of the hop is extracted during the boil. The aroma is provided by aroma hops whose essential oils provide the aroma. Each variety of hops has its own distinct flavor/aroma profile. Yeast are unicellular fungi. Yeast is the most essential, yet least understood aspect of brewing beer. Since the 1850s, it has been scrutinized by such famous scientists as Pasteur, Guy-Lussac, and van Leeuwenhoek. Most brewing yeast belongs to the genus Saccharomyces.
The yeast converts the sugars in the wort into alcohol. The first stage of this process is called the "lag" phase, marked by the breaking of proteins into their constituent amino acids. The ferment then enters the "respiration" phase, where the yeast absorbs oxygen and reduces the pH of the wort, so that it becomes acidic and anaerobic. The yeast breaks down the glucose sugars into carbon dioxide, water, and pyruvic acid. Pyruvic acid later becomes alcohol. Yeast cannot ferment all sugars, which is why beer still has a sweet taste at the end of the ferment. The strain of yeast will impart its own flavor although malt and hops are the main flavor components. Yeast that adds little in the way of flavors are usually described as having a "clean taste". Yeast produce three metabolic by-products that affect beer taste: phenols - spicy or clove like taste or medicinal taste; esters - a fruity taste; Diacetyls - a butterscotch or "woody" taste. The presence of any of these flavor components depend largely on the style of beer being brewed. Much depends on individual palates and the effect the brewer is aiming for. |
