Flavour precursors: contribution to wine aroma, in-mouth sensory properties and flavour release
A critical aspect of wine quality from a consumer perspective is the overall impression of the wine in the mouth. Wine flavour is driven by volatile compounds (including ethanol), and also by non-volatiles such as sugars, salts, acids and phenolic compounds including tannins, polysaccharides and proteins. Overall flavour is also potentially derived from non-volatile precursor compounds, such as glycosides (compounds joined to sugars) or amino acid conjugates that can be broken down in-mouth, thereby releasing volatile aromas. The individual wine components alone are not sufficient to achieve a desirable in-mouth perception; this can only be obtained through the interaction of multiple components.
This project has the overall aim of establishing the extent to which wine flavour is due to precursor compounds releasing flavour compounds in-mouth. The persistence and intensity of fruit flavour are very important aspects of wine quality, and grape-derived compounds that are non-volatile, but which can be degraded during the tasting process to produce flavour, are a potentially important source of desirable flavour that has not been previously investigated.
Enhancing flavour precursors in winemaking
Previous work in this project demonstrated the potential of non-volatile glycosides as flavour precursors. The results showed that there is a surprising ability of in-mouth enzymes, most likely from salivary bacteria, to quickly liberate volatile aroma compounds from their bound form during wine drinking, enhancing flavour and contributing to a lingering aftertaste. This mechanism of flavour release seems to be fairly variable across individuals, suggesting one reason for variation in people’s sensory perception and preferences. To follow up this work, a vintage experiment was completed to address possible ways winemakers might increase the contribution of these precursors in their wines. Several sets of grape juices were treated to boost their level of glycosides and fermentations have been completed. Sensory studies will show whether these treatments have resulted in more intense or complex wines.