Smoke from simulated forest fire alters secondary metabolites in Vitis vinifera L. berries and wine

Abstract

The exposure of Vitis vinifera L. berries to forest fire smoke changes the concentration of phenylpropanoid metabolites in berries and the resulting wine. The exposure of Vitis vinifera L. berries (i.e., wine grapes) to forest fire smoke can lead to a wine defect known as smoke taint that is characterized by unpleasant "smoky" and "ashy" aromas and flavors. The intensity of smoke taint is associated with the concentration of organoleptic volatile phenols that are produced during the combustion-mediated oxidation of lignocellulosic biomass and subsequently concentrated in berries prior to fermentation. However, these same smoke-derived volatile phenols are also produced via metabolic pathways endogenous to berries. It follows then that an influx of exogenous volatile phenols (i.e., from forest fire smoke) could alter endogenous metabolism associated with volatile phenol synthesis, which occurs via the shikimic acid/phenylpropanoid pathways. The presence of ozone and karrikins in forest fire smoke, as well as changes to stomatal conductance that can occur from exposure to forest fire smoke also have the potential to influence phenylpropanoid metabolism. This study demonstrated changes in phenylpropanoid metabolites in Pinot noir berries and wine from three vineyards following the exposure of Vitis vinifera L. vines to simulated forest fire smoke. This included changes to metabolites associated with mouth feel and color in wine, both of which are important sensorial qualities to wine producers and consumers. The results reported are critical to understanding the chemical changes associated with smoke taint beyond volatile phenols, which in turn, may aid the development of preventative and remedial strategies.

Review of the Effects of Grapevine Smoke Exposure and Technologies to Assess Smoke Contamination and Taint in Grapes and Wine

“…It has been demonstrated that grapevine smoke exposure changes the chemical composition of grape berries, and wine produced from these berries possesses objectional smoky aromas such as "burnt wood", "ashy", and "smoked bacon" [11,16,26]. These aromas are thought to be derived primarily from phenolic compounds present in smoke (Figure 1), particularly guaiacol and 4-methylguaiacol, which are thought to exhibit "smoky", "burnt wood", "musty", and "phenolic" aromas [11,34].…”

“…Unfortunately, climate change effects, such as increases in temperature, winds, and drought, have led to more favorable bushfire conditions [7][8][9][10][11][12][13]. Recent climate research predicts an increase of 15-70% in the number of days of "very high" or "extreme" fire danger by 2050 and a lengthening of the fire season, resulting in more frequent and intense bushfires [12][13][14][15][16].…”

Classification of Smoke Contaminated Cabernet Sauvignon Berries and Leaves Based on Chemical Fingerprinting and Machine Learning Algorithms

“…Research by Noestheden et al [ 5 ] found that smoke exposure induced changes in phenylpropanoid metabolites in Pinot Noir berries and wine, some of which are associated with the color and mouthfeel of the wine. Berries exposed to HS and LS treatments had the highest mean NAI values, indicating that smoke exposure may increase anthocyanin content, possibly due to an increase in phenolic accumulation as a stress response induced by exposure to ozone present in smoke [ 5 , 79 , 80 ]. The HSM treatment had a low NAI value, indicating that misting may reduce anthocyanin concentrations through increased irrigation.…”

“…The incidence and intensity of wildfires are increasing worldwide, mainly due to the effects of climate change [ 1 , 2 , 3 , 4 , 5 ]. Bushfires that occur near wine regions can result in grapevine smoke exposure, which can alter the chemical composition of grape berries.…”

Detection of smoke-derived compounds from bushfires in Cabernet-Sauvignon grapes, must, and wine using Near-Infrared spectroscopy and machine learning algorithms

“…Recent climate change forecasts have predicted an increase in the number and intensity of wildfires, as well as a lengthening of the fire season in many grape-growing regions throughout the world, including Australia, Greece, California, Chile, and South Africa (CSIRO & Australian Government Bureau of Meteorology, 2018;Favell et al, 2019;Fuentes et al, 2019;Hughes & Alexander, 2017;Noestheden et al, 2018b;Simos, 2008). As a consequence, the incidence of grapevine smoke exposure and the subsequent development of objectional smoky aromas in wine known as smoke taint is also likely to increase, resulting in significant financial losses to the wine industry (Bell et al, 2013;Kelly et al, 2012;Kennison et al, 2011;Noestheden et al, 2018a;Noestheden et al, 2017).…”