Evaluating the potential for particulate matter sensors to predict smoke taint risk in the vineyard

Abstract

Vineyard exposure to wildfire smoke can contaminate grapes due to the uptake of smoke-derived volatile phenols.1 Smoke density, the duration of smoke exposure, and winemaking decisions influence the concentration of free and glycosylated volatile phenols in wine, and consequently, the perception of undesirable ‘smoky’ characters.2,3 Climate change is expected to increase the frequency and severity of fires; thus, it is likely the issue of ‘smoke taint’ will continue. As such, the (global) wine industry would benefit from the development of real-time methods for assessing vineyard smoke exposure. This project evaluated the potential for particulate matter (PM) sensors to monitor smoke exposure in the vineyard, and thus, smoke taint risk. PurpleAir PM sensors were deployed alongside excised bunches of grapes during prescribed burns conducted by the Department for Environment and Water in several South Australian national parks. Smoke emissions were monitored as particulate matter (PM2.5) concentrations (at different distances upwind and downwind of the burn site), while the uptake and glycosylation of smoke-derived volatile phenols by grapes determined the extent of smoke contamination. The sensors enabled temporal changes in smoke density to be monitored during each burn, and demonstrated the rapid dispersion of smoke. Higher free and glycosylated volatile phenol concentrations were observed in grapes positioned closer to the burn, attributable to exposure to higher density smoke. Model smoke experiments were subsequently undertaken to further evaluate sensor performance. While the density of smoke generated within a purpose-built smoke chamber (specifically designed for smoke taint research) saturated the sensors, smoke emissions were successfully monitored during a field trial simulating vineyard smoke exposure. The density of smoke was monitored over 5 hours and grapes exposed to higher PM yielded wines with increased smoke taint marker concentrations and perceivable smoke characters. By deploying PM sensors in vineyards, grape and wine producers would have access to real-time data regarding both the duration of smoke exposure, and the density of smoke. Where no or low PM measures are returned, industry can confidently proceed with harvest. Where PM data suggests prolonged exposure to smoke, especially dense smoke, informed decisions regarding the need for further testing and/or implementation of remediation strategies can be made, prior to harvest.

References

1. Krstic et al. (2015) Aust. J. Grape Wine Res. 21:537−553.