Wine connoisseurs can easily distinguish a dry red, such as Cabernet Sauvignon, from a fruitier red, such as Pinot Noir. Scientists have long linked the "drought" sensation in wine to tannins, but how these molecules create their characteristic mouthfeel over time is not fully understood. Now researchers have determined that tannin structure, concentration and interactions with saliva and other wine constituents influence the perception of drought.
The dryness sensation, also known as astringency, refers to a wrinkling or rough feeling in the mouth when drinking wine. Scientists know that wine drinkers experience sensitivity when tannins and saliva proteins interact, aggregate and precipitate, leaving the mouth less lubricated. But the researchers wanted to investigate how tannins from two different wines interact with other characteristics of the drinks, and with saliva proteins, to influence dryness perception.
The researchers extracted the tannins from a dry (Cabernet Sauvignon) and less dry (Pinot Noir) red wine. Through various analyses, they found that the Cabernet Sauvignon contained more, larger and more pigmented tannins than the Pinot Noir, and these tannins formed more protein aggregates in saliva. Trained sensory panelists perceived the Cabernet to be drier with a longer drying time than the Pinot. Interestingly, when the opposite type of tannin was put in cabernet or pinot wines, the panelists were unable to detect differences in dryness. So, for example, when Cabernet tannins were added to a Pinot wine, the drink appeared to have the same dryness as the original Pinot. When Cabernet tannins were added to a model wine (ethanol and tartaric acid in water), panelists rated the dryness intensity and duration that was greater than that of the original model wine. Therefore, the distinctive aromas of the two red wines likely influenced the panelists' perception of dryness, preventing them from noticing the added tannins.
