# Impact of Yeast Selection on Volatile Phenol Levels of Wines Produced from Smoked-Exposed Juice
###### Abstract  
Grapes exposed to smoke can result in wines that have unacceptable high levels of volatile phenols. High volatile phenols levels have a negative impact on wine quality. This study aimed to determine the levels of volatile phenols in wines produced from smoke-exposed juice by a selection of commercial wine yeasts and to determine if yeast selection affected the perception of smokiness in wine. Commercial white and red wine yeasts were screened for the production of volatile phenols in smoke-exposed Chenin Blanc and Merlot juice. Volatile phenol levels were determined by GC-MS/MS and wines were also subjected to sensory evaluation. Volatile phenol levels in smoked wines varied and was affected by yeast strain. The highest guaiaicol levels in Chenin Blanc were found in wines fermented with QA23, while Merlot wines that underwent spontaneous alcoholic fermentation contained the highest levels. The levels of volatile phenols differed significantly between the smoked and unsmoked wines, and the sensory results supported the chemical data. Volatile phenols had a negative effect on Chenin Blanc flavor profiles even when the levels were below odor detection thresholds. Yeast selection is important and can affect the volatile phenol levels and flavor profiles of wines.  
y 2021 25 September 2021 26 October 2021 2021 25 September 2021 26 October 2021 25 September 2021 26 October 2021 25 September 2021 25 October 2021 25 September 2021 25 October 2021 25 September 2  
ferentation, or when hydrolyzed with strong acid or \(\beta\)-glucosidase enzymes. Guaiacol imparts a smoky, burnt character and has the lowest aroma detection threshold of the volatile phenols [14].  
Yeasts present on grapes and winery equipment or added as starter cultures [15] are responsible for transforming grape must into wine through alcoholic fermentation. Yeasts also contribute to wine flavor and quality through the production and excretion of metabolites [16]. While many of the early knowledge gaps about the effect of smoke on grape and wine composition have been investigated, only [PERSON] et al. [11] reported on the effect of yeast selection on the concentration and sensory impact of smoke-derived volatiles in wine. [PERSON] et al. [11] investigated the varying ability of eight yeast strains to affect the concentration of volatile phenols and sensory profiles of Grenache wines, and proposed that selected yeast strains could be used to alter smoke-related aromas, flavors, color and chemical composition of wines. The occurrence of wildfires are unpredictable so the source of naturally smoke affected grapes is limited. During smoke trials, vines and grapes are usually smoked in purpose built tents, where smoke is then pumped into these enclosures [4; 5; 11]. To circumvent these logistical limitations of smoking the grapes on the vine, this study exposed the grape juice to smoke and fermented with various yeast strains. The aims of this study were to determine if there were differences in the volatile phenol levels in wines fermented with the selected commercial white and red wine yeasts, and to ascertain if yeast selection could change or mask the perception of smokiness in wine prepared from smoke-exposed juice. This was accomplished by measuring volatile phenol marker compounds and conducting sensory evaluations.