texture and mouthfeel are essentially synonymous terms for the tactile properties of a spirit—for the level and quality of its thickness or viscosity. “Weight” is often used in a similar fashion, although it is not strictly synonymous. Texture is the product of several distinct factors, including alcohol levels, glycerol and sugar content, and the presence of tannins and phenols, as well as of trace elements such as polysaccharides, sterols, and other compounds, some of which are not fully understood. Of all these factors, residual or added sugar generally offers the most dramatic (and easily detectible) impact on the mouthfeel of a spirit.
A spirit’s alcohol level is also very important in forming its texture. Paradoxically, an aged spirit at 50 percent ABV will carry more perception of weight for most tasters than the same spirit at 30 percent, even though alcohol is physically lighter than water. But alcohol is a sugar and has its own viscosity. Tasters may also differentiate between the mouthfeel of unaged spirits at the same or similar alcohol percentages, whether this is due to perceived quality of spirit or innate compounds. For instance, among vodkas, water used for dilution may be utterly neutral or it may have mineral content that creates a greater palate impression—adding texture and mouthfeel.
With oak-aged spirits, time in barrels can add elements that contribute to texture: tannins, phenols, furans, lactones, glycerols, and various sugars (including arabinose, fructose, glucose, and xylose) often increase with time in barrels due to the processes of extraction and concentration inherent in barrel aging. See maturation. Sterols such as beta-sitosterol also seem to originate during alcohol’s sojourn in oak containers; these too can add to mouthfeel and texture.
Tannins will bind with salivary proteins, creating the sensation of dryness, bitterness, friction, and astringency. Somatosensation provides more information through thermoreceptors (for temperature responses), mechanoreceptors (for pressure or viscosity), proprioceptors (which help us identify muscle movements, including those of the tongue), or even nociceptors (pain sensors).
Additionally, some proteins may generate physiochemical responses that can affect textural perception, particularly those associated with the coolness of mint or the heat sensation provided by capsaicin. These may not add directly to a sensation of weight but have a direct impact on texture. Nerves in our mouths contain a protein called TRP-V1 that generally indicates a rise in temperature. Capsaicin, by activating that protein, tricks the brain into believing that something is hot. Conversely another protein, TRPM8, is activated by cold temperatures as well as by menthol, mint, and eucalyptus oil; this cooling sensation may make a spirit seem lighter and crisper than it might be perceived were they not present.
See also tasting spirits.
Buxton, Ian, and Paul S. Hughes. The Science and Commerce of Whisky. London: RSC, 2015.
Jeffrey, David W, Gavin Sacks, and Andrew Waterhouse. Understanding Wine Chemistry. Chichester, UK: Wiley, 2016.
Shepard, Gordon M. Neuroenology. New York: Columbia University Press, 2016.
By: Doug Frost