Ethers and phenols in beer: what is the difference
Fruit shades that can be felt in beer are usually
formed by yeast if the recipe does not have real fruits. During the fermentation process, a reaction occurs between the organic acids present in the wort and the resulting ethyl alcohol. Its result is the appearance of ethers. Most often, esters can manifest themselves in the form of the aroma of banana, pear, apple, honey, rose, and in some cases, solvents.
Since the formation of esters occurs as a result of the reaction between alcohol and acids, there are three factors that can influence the course of this process. Understanding and managing them, the brewer can achieve the required level of esters in beer.
A high content of sugars, zinc and free amino acids leads to increased formation of esters in beer. High concentrations of dissolved oxygen and lipids, on the contrary, can reduce the formation of ethers.
A Brief History of Hefeweitsen – German Wheat Beer
Certain yeast strains are more prone to ester formation. For example, the yeast used for the production of German wheat beer is prone to the formation of an increased amount of isoamyl acetate, which gives a banana flavor characteristic of this style of beer. Basically, ale yeast strains form more esters during fermentation than lager strains. But this is due primarily to a higher fermentation temperature.
You can believe it or not, but the shape of the fermentation tank affects the formation of ethers. Narrow and high fermenters reduce the formation of ethers compared to open and lower fermentation tanks. This is due to the hydrostatic effect and the increased content of CO2, which is typical for narrow and high fermenters.
Some types of phenols or polyphenols are always present in beer. But when tasters pick up definitions for phenols or describe beer as “phenolic,” they mean flavors of volatile phenols. In most cases, the presence of phenols is undesirable, but there are exceptions for certain styles of beer. Phenols are felt in beer even in small concentrations and manifest themselves in the form of aromas of cloves, drugs or smoke. Volatile phenolic compounds can enter beer in three different ways.
Ingredients: Water or Smoked Malt
Water may contain phenols, which do not evaporate during the process of boiling the wort and enter the product. Smoked malt introduces polyphenols into the beer, which give the beer an earthy and smoky hue that resembles the smell of a fire. When a brewer makes smoked beer, these flavors are desirable. Hops and malt can also be sources of polyphenols in the form of tannins, which are felt more in taste than in aroma.
Water in beer: effect on taste and water treatment
Chlorine and bromine usually stimulate the formation of a large number of phenols and polyphenols. Chlorine is often found in water, so it must be processed. Chlorine can also enter the product through equipment that has been cleaned with chlorine-based products and not thoroughly washed. Phenols formed on the basis of chlorine and bromine are manifested in beer by the smells of an antiseptic or combustion products, respectively.
Yeast and / or bacteria
For example, clove notes are often found in German wheat beer and in many Belgian varieties. This is due to the presence of the 4-vinyl guaiacol compound, which is formed by decarboxylation of ferulic acid. If the brewers want to achieve a more pronounced clove in beer, then it is necessary to increase the content of ferulic acid in beer. This can be achieved by selecting a specific yeast strain, by having a temperature pause of 45 ° C during mashing, or by fermentation at higher temperatures. In addition, the presence of an earthy aroma in beer is associated with certain phenols that are produced by various strains of Brettanomites.