Can varietal ‘apricot’ aroma of Viognier wine be controlled with clonal selection and harvest timing?

Recent wine-like reconstitution sensory studies confirmed that several monoterpenes were the key aroma compounds in the perception of an ‘apricot’ aroma attribute in Viognier wine. Other aroma compounds, including a set of aldehydes and several γ-lactones, were also indicated to be related to ‘apricot’ aroma in that study, but the addition of these compounds to the reconstitution gave ambiguous results. 

To investigate these interactions, further reconstitution sensory studies were conducted. Firstly, in a wine-like model matrix, the aldehydes were found to suppress ‘apricot’ aroma intensity, while γ-lactones significantly enhanced the intensity of ‘apricot’, but only in the presence of a higher concentration of monoterpenes. Secondly, a neutral Chardonnay wine base spiked with the monoterpenes and γ-lactones together, or with only the monoterpenes added, was considered to have a similar ‘apricot’ aroma to a typical Viognier wine, whereas if spiked with only γ-lactones, then its aroma was not similar. Finally, a sensory difference study was conducted by comparing single or double strength γ-lactones in Chardonnay wine with added monoterpenes. No significant difference was found between the monoterpene-spiked Chardonnay wine and when γ-lactones were also added. Thus, γ-lactones are unlikely to impart or enhance ‘apricot’ aromas in white wine. 

Monoterpenes are grape-derived aroma compounds, but little is known regarding their accumulation in Viognier grapes. Having established the importance of monoterpenes to the perception of varietal ‘apricot’ aroma in Viognier wines, it is likely that controlling their concentration in the grapes can influence the ‘apricot’ aroma intensity in the resultant wine. 

To establish if clonal selection and harvest timing could be used as tools to modulate ‘apricot’ aromas in Viognier wines, vineyard studies were conducted. Eleven Viognier clones were assessed over three vintages. Large differences were found in the concentration of the monoterpenes between the clones. In a further study of four Viognier clones, two clones showed similar monoterpene concentration profiles throughout ripening, but the other clones were substantially lower in monoterpene concentration. Subsequently, a winemaking study was carried out to assess the effect of clone and grape ripeness on ‘apricot’ character in Viognier. Grapes from two Viognier clones were both picked at two ripening timepoints and from two wine regions with different climates. 

Author: Tracey Siebert 

The Australian Wine Research Institute, P.O. Box 197, Glen Osmond (Adelaide), SA, 5064, Australia 

Email: tracey.siebert@ari.com.au 

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