Month: May 2009

The body of a beer is characterized as the fullness of the flavor and mouthfeel, and descriptors range from watery or characterless to satiating or thick. Body is technically separate from mouthfeel, which encompasses physical sensations such as astringency, alcoholic warmth and carbonation, but the combination determines how the beer stimulates the palate. The body is determined by the levels of dextrins and medium-length proteins. Lack of dextrins is caused by low saccharification temperatures, excessive use of adjuncts or by highly attenuative yeast strains. A low protein level may be caused by excessively long protein rests, excessive fining or the addition of large amounts of fermentable sugars. Light body is appropriate in American light lagers and lambics, but not in malt-accented styles such as barleywines and doppelbocks.

Bitterness, or rather excessive bitterness, is perceived as a harsh dry taste on the back of the tongue. It is usually due to over-hopping, especially when high alpha hops are used. Roasted malts and high concentrations of magnesium and sulfate ions also contribute to the overall bitterness. Bitter compounds may also be produced by oxidation or contamination by wild yeast, in which case there are usually other off-flavors. High levels of hop bitterness are appropriate in IPAs and barleywines, while bitterness due to roasted barley/malt is appropriate in robust porters and dry stouts.

This flavor is a mouthpuckering sensation that is comparable to chewing on grape skins or grape seeds. It is often produced by the extraction of tannins from grain husks due to overcrushing oversparging, or sparging with alkaline or boiling water. Astringency may also be produced by polyphenols that result from spoilage by acetobacter or wild yeast. Another possible source is oxidation, in which case the responsible compounds are polyphenols and aldehydes. Finally, spices such as coriander, orange peel and cinnamon also contribute astringent flavors, but these tend to mellow with age. Note that over-attenuation and low dextrin levels can increase the perception of astringency.

This flavor may be detected as a spicy, vinous character in the aroma and taste and is often accompanied by a warm or prickly mouthfeel. The simplest and most prevalent alcohol in beer is ethanol, which is produced by the fermentation of glucose and other reducing sugars. Higher, or fusel, alcohols are usually present at sub-threshold concentrations, but elevated levels are associated with underpitching, low levels of dissolved oxygen prior to pitching or low levels of free available nitrogen (FAN). These deficiencies force the yeast to metabolize fatty acids in the trub as a source of oxygen and carbon, producing a greater fraction of long chain alcohols. High gravity worts and high fermentation temperatures also tend to increase the concentration of these higher alcohols through increased yeast activity. Alcoholic characteristics are desired in strong ales and lagers as long as they are not coupled with the solvent notes associated with elevated ester or fusel alcohol levels.

This compound has the taste and aroma of fresh-cut green apples, and has also been compared to grass, green leaves and latex paint. It is normally reduced to ethanol by yeast during the secondary fermentation, but oxidation of the finished beer may reverse this process, converting ethanol to acetaldehyde. Elevated levels are generally present in green beer or if the beer is prematurely removed from the yeast. It can also be a product of bacterial spoilage by Zymomonas or Acetobacter. Background levels of acetaldehyde can be tasted in Budweiser due to the use of beechwood chips to drop the yeast before it can be reduced to ethanol.