The Oxford Companion to Beer definition of
Mouthfeel can be defined as the textural attributes of beer, those which produce a tactile sensation in the mouth. The sensations associated with mouthfeel are physical qualities of beer and should be considered a major attribute when evaluating beer, along with aroma and flavor. There are three key attributes recognized in the perception of mouthfeel: carbonation, fullness, and aftertaste. Carbonation is often the first attribute perceived in the mouth. It is felt as a particular sting or tingle that is linked to the amount of carbon dioxide in a beer. Bubble size and foam volume, too, are related to carbon dioxide. Beers pressurized with large volumes of nitrogen have a tight foam and tiny bubbles, which produce a creamy mouthfeel. See carbonation. Fullness refers to the perceived weight and flow resistance of a beer while it is being consumed. Terms used to describe fullness are density and viscosity. These are sensations associated with the body of the beer. Whereas wine contains glycerol and other compounds that promote palate fullness, beer often contains unfermentable dextrins in a similar role. These complex sugars, developed during the mashing process, can contribute mouthfeel to a beer without necessarily increasing perceived sweetness. Beers that seem to lack proper fullness might be described as “thin,” whereas very full-bodied beers can range from “round” all the way up to “syrupy.” “Afterfeel,” the final attribute of mouthfeel, is an integral part of a beer’s finish. It is associated with the lasting sensations recognized in the mouth. Such attributes as stickiness, astringency, dryness, bitterness, oiliness, or mouth-coating characteristics can leave a well-defined afterfeel that may linger. Although not well understood, mouthfeel is strongly influenced by a beer’s raw materials and brewing techniques. Aside from adjustments to ingredients and technique, brewers also can use water chemistry to influence mouthfeel, adding salts such as sodium chloride to enhance a perception of body and complexity. See also sodium chloride.
Bamforth, Charles. “Eyes, nose, and throat, the quality of beer.” In Beer: Tap into the art and science of brewing, 2nd ed., 78–9. New York: Oxford University Press, 2003.
Langstaff, Susan, J.-X. Guinard, and Michael Lewis. Sensory evaluation of the mouthfeel of beer. American Society of Brewing Chemists 49 (1991): 54–9.