2018 Oenology paper of the year

Dr Paul Boss
CSIRO Agriculture & Food

Boss, P. , Kalua, C. , Nicholson, E. , Maffei, S. , Böttcher, C. and Davies, C. (2018), Fermentation of grapes throughout development identifies stages critical to the development of wine volatile composition. Australian Journal of Grape and Wine Research, 24: 24-37. doi:10.1111/ajgw.12296

Dr Boss’s paper was selected by the committee because it demonstrated really interesting information about chemical analysis of Cabernet sauvignon and Riesling over the course of berry development, this information has a direct application for winemakers who can tailor their wine style from the vineyard.

Authors left to right: Paul Boss, Chris Davies, Sue Maffei, Christine Böttcher, Curtis Kalua and Emily Nicholson.

The work described in the paper was a response to frequent statements from wine industry participants about a dis-connect between sugar ripeness and flavour ripeness as vintages have become compressed as well as the general perception that flavour and aroma compounds accumulated in the later stages of grape ripening. To explore this we made wine from grapes harvested every fortnight starting two weeks after fruit set through to ripening, after normalising the sugar content, and analysed the volatile compounds in the wines. There was a subset of compounds that increased after veraison, but interestingly many of these were esters that are produced by yeast during fermentation. Understanding how grape compositional changes during ripening influences the production of these yeast-derived compounds will improve our ability to manage wine flavour in the vineyard. What was also interesting was that there were many more compounds that decrease in concentration in the wine as the fruit ripens than there are that increase. So it is important to remember that compounds that produce potentially negative characters in wines need to decease during the ripening period and this may be where the sugar/flavour nexus is disrupted, especially if this decrease is reliant on time.

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