Aeration of red ferments has a definite and reproducible positive impact on wine quality.
That’s the conclusion of a Wine Australia-funded study conducted by Australian Wine Research Institute Research Manager, Dr Simon Schmidt, which found that aeration during fermentation of red wines has the potential to enhance positive red fruit attributes and suppress less desirable reductive characteristics.
The study has been published in the latest issue of Australian Journal of Grape and Wine Research.
‘Much of the previous research on the use of aeration during fermentation has focused on white wine production. Uptake of aeration as a tool in winemaking has been impeded by the lack of clear information about how it applies to red winemaking. This includes an understanding of the major benefits of its use, and the nature of the aeration regimes required to modify the finished product’, Simon said.
‘Our study aimed to evaluate the impact of different modes of aeration – varying in their timing, duration and intensity – on fermentation duration, chemical composition and sensory properties of Shiraz wine.’
The study involved treating 48 fermentations – each at a scale of 450 kilograms – with different aeration regimes across four vintages. The aeration treatments were then compared to non-aerated fermentations.
‘We found that the effects of aeration were reproducible across vintages and resulted in enhanced red fruit-related attributes of the Shiraz wine, in addition to decreases in astringency, bitterness and colour intensity.’
Simon said the study’s strength was the number of independent experiments (four vintages) that demonstrated the key effects of enhanced red fruit characters and suppression of reductive characters.
‘We had observed this in previous work but it was great to see that these effects of aeration were reproducible. This body of work should give winemakers confidence that if they are able to implement effective aeration regimes, then they will see the same outcomes that we observed.’
Simon said that the perception of red fruit and reductive characters in red wine is linked, with low molecular weight volatile sulfur compounds responsible for reductive characters able to suppress the perception of red fruit attributes derived from esters.
‘Aeration helps to bring out the red fruit characters of wine by decreasing the concentration of low molecular weight sulfur compounds. However, this is not the only way that aeration enhances red fruit character; it is also through the enhanced production of compounds directly responsible for those characters.
‘So the action of aeration is two-fold. First through stimulation of compounds that impart red fruit character and secondly through the suppression of compounds that impair the ability to perceive those characters.’
While there are many reasons why you might want to consider aerating a red ferment, Simon said winemakers should not expect improved fermentation performance to be one of them. Decreases in the duration of aerated ferments were not observed in any of the four vintages.
Simon also said that winemakers should be confident in conducting their own aeration trials in red ferments. ‘Red ferments are very resilient when it comes to aeration and the risk of oxidative effects such as elevated volatile acidity is extremely low.
‘The main challenge that a winemaker will face will be to get enough air into the ferment such that the beneficial effects will be realised.’
