Evaluation of the impact of different amelioration techniques on the chemical composition and sensory characteristics of smoke impacted wines

Abstract

AIM: The increasing incidences of wildfires in wine grape growing regions pose a significant risk. Persistent exposure to smoke can compromise the quality and value of wine grapes and adversely affect wines made from smoke exposed grapes. A wine is seen as smoke impacted or tainted when there is an overpowering smoky, medicinal, chemical, burnt or ashy aroma on the nose and a distinctive retronasal ash tray-like character in the mouth. The aim of this study was to evaluate the different wine smoke taint treatments available.

METHODS: The different amelioration techniques were investigated using smoke impacted wines made from Cabernet-Sauvignon grapes from Napa and Lake Counties (UC Davis Teaching and Research Winery) in 2017 and 2018. Treatments included enzyme additions with varying pectolytic and glycosidase activities (Lafazym AROM, Lyvarome A5, Sumizyme BGA and Zimarom at 2 and 4 g/hL), allowing reaction time of up to 6 weeks. Additionally, wines were treated by fining (activated charcoal and molecular imprinted polymers), reverse osmosis (standard and differential filtration procedures) and spinning cone technology. The impact on wine composition, specifically smoke taint marker compounds (both free and bound volatile phenols as determined by GC-MS/MS and LC-MS/MS) as well as other key volatile (GC-MS) and non-volatile (RP-HPLC) compounds important for wine quality were evaluated. Additionally, descriptive analysis of the wines were performed using 12 panelists. Multivariate statistics were used to relate wine composition to sensory attributes.

RESULTS: In this study enzyme treatment did not result in a significant increase in free volatile phenols, irrespective of enzyme, treatment time or addition concentration. Indicating that the selected enzymes were unsuccessful in hydrolyzing the bound volatile phenols. Fining, reverse osmosis and spinning cone technology were successful in decreasing smoke taint markers (both free and bound volatile phenols), however significantly more free then bound volatile phenols were removed. Treatments were also able to decrease smoke taint-related sensory attributes in the smoke impacted wines. However, efficacy depended on the individual wine matrixes. Additionally, treatments lacked specificity and removed more then just volatile phenols from the wines, impacting flavor attributes other then those related to smoke. In general, the overall impact depended on the level of treatment needed and the decrease in mouthfeel for instance can be countered through blending or addition of commercial wine products.

CONCLUSIONS

Amelioration techniques are not 100% fixes of smoke taint but can significantly decrease smoke taint perception. Further research is needed to determine the feasibility of treatment success based on the wine matrix so that winemakers can make informed decisions.