Abstract
Wine aroma is an important quality trait in wine, influenced by its volatile compounds. Many factors can affect the composition and levels (concentration) of volatile aromatic compounds, including the water status of grapevines, canopy management, and the effects of climate change, such as increases in ambient temperature and drought. In this study, a low-cost and portable electronic nose (e-nose) was used to assess wines produced from grapevines exposed to different levels of smoke contamination. Readings from the e-nose were then used as inputs to develop two machine learning models based on artificial neural networks. Results showed that regression Model 1 displayed high accuracy in predicting the levels of volatile aromatic compounds in wine (R = 0.99). On the other hand, Model 2 also had high accuracy in predicting smoke aroma intensity from sensory evaluation (R = 0.97). Descriptive sensory analysis showed high levels of smoke taint aromas in the high-density smoke-exposed wine sample (HS), followed by the high-density smoke exposure with in-canopy misting treatment (HSM). Principal component analysis further showed that the HS treatment was associated with smoke aroma intensity, while results from the matrix showed significant negative correlations (p < 0.05) were observed between ammonia gas (sensor MQ137) and the volatile aromatic compounds octanoic acid, ethyl ester (r = −0.93), decanoic acid, ethyl ester (r = −0.94), and octanoic acid, 3-methylbutyl ester (r = −0.89). The two models developed in this study may offer winemakers a rapid, cost-effective, and non-destructive tool for assessing levels of volatile aromatic compounds and the aroma qualities of wine for decision making.
Highlights
Wine aroma is a critical component of wine quality and is determined by the combinations and complex interactions of numerous volatile compounds [1,2,3]
This study explored the use of a low-cost and portable e-nose to assess volatile aromatic compounds and smoke aroma intensity in wines produced from grapes exposed to different densities of smoke exposure with or without in-canopy misting
The volatile aromatic compounds observed are fatty acid esters formed during fermentation by yeast, with high levels arising in the LS treatment potentially due to increased fermentation activity
Summary
Wine aroma is a critical component of wine quality and is determined by the combinations and complex interactions of numerous volatile compounds [1,2,3]. It has been predicted that the effects of climate change may have profound impacts on the aromatic potential of grapes and wine quality [11], the increased risk and incidence of bushfires, resulting in grapevine smoke exposure and smoke taint in wines [12,13,14]. Grapevine exposure to smoke during the critical stages between veraison and harvest has been shown to alter the volatile aromatic composition of grapes and lead to the development of smoke taint in wine, resulting in objectionable smoky characters and reduced wine quality [12,13,14,15,16]. Increases in temperature and drought brought on by climate change can affect the aromatic compounds in grapes and wine quality [11,17]
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