Analysis and amelioration of smoke taint in wine

Abstract

The occurrence of smoke taint in wine is of worldwide concern for grape growers, winemakers and the wine industry. An improved understanding of the impact of bushfire smoke on grapes and wine is important to enable industry to overcome this challenge. Smoke taint occurs when vineyards are exposed to smoke from bushfires or prescribed bums and can result in wine which exhibits undesirable smoky and ashy aromas and flavours. The prior research summarised in Chapter 1 addresses many of the early knowledge gaps concerning the impact of smoke on grape and wine quality such as: the composition of smoke taint, including identification of several of the volatile compounds involved, and the complex sensory properties imparted to wine that cause the detrimental effects to wine quality. However, these studies do not offer industry many practical solutions to mitigate the incidence or severity of smoke taint. This research reported in Chapter 2 describes several methods for ameliorating smoke taint in wine; i.e. the efficacy of (i) reverse osmosis (RO) and solid phase adsorption, and (ii) commercial fining agents, as treatments for smoke tainted wine. The ability of these methods to reduce the perception of smoke-related sensory attributes and concentrations of smoke-derived volatile phenols are described in two papers, which form the basis for this chapter on the amelioration of smoke taint in wine. The studies reported in Chapter 3 describe the use of spectroscopy as a rapid analytical method for screening wines for smoke taint. The capability of spectroscopic techniques, in combination with chemometrics, to be used for the classification and discrimination of wine are also introduced. The need for rapid detection of smoke taint in grapes and wines was identified as a priority for industry following the demand for analysis of grapes and wine after a fire event. Winemakers operate under considerable time and resource constraints during vintage, thus rapid determinations of fruit quality, including the assessment of smoke exposure by fruit, are required. A predictive method employing mid-infrared (MIR) spectroscopy was developed by scanning control and smoke-affected wines, and applying multivariate data analysis techniques to the resulting data, to generate a calibration model for the classification of smoke tainted wines. Two-dimensional correlation spectroscopy (2D-COS) was also investigated as a novel method for characterising smoke taint in wines. Again, two papers are presented as the basis for a chapter concerning the spectroscopic analysis of smoke taint in wine.