Aeration of Vitis vinifera Shiraz fermentation and its effect on wine chemical composition and sensory attributes

Background and Aims Aeration during fermentation of red wines has the potential to enhance positive red fruit attributes and suppress less desirable reductive characteristics. The implementation of aeration in commercial winemaking, however, is impeded by the lack of a clear understanding of both the major benefits of its use and the nature of the aeration regimes required to modify the finished product. This work 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. Methods and Results Forty-eight pilot-scale fermentations (450 kg) were treated with different aeration modalities and compared to non-aerated fermentations across four vintages. This work demonstrated the reproducible effects of aeration, resulting in an enhancement of fruit-related attributes, decreases in colour intensity and a lowering of astringent mouthfeel and bitterness. The development of attributes describing possible oxidation or undesirable volatility were not observed in this work. These effects on wine sensory attributes were correlated with an increase in the concentration of relevant short and branched-chain esters and acetates, and a decrease in the concentration of phenolic substances. No enhancement of fermentation performance was observed in any of the trials. Overall, this work revealed the robustness of red wine fermentations to aeration. Conclusions This work provides strong evidence that aeration does not alter the duration of either alcoholic or malolactic fermentation of red musts. Although there was no impact on fermentation performance, aeration did result in the production of wines with increased red fruit characters, and decreased astringency and reductive off-odours. Significance of the Study This work demonstrates aeration to be a useful oenological tool for the production of red wine and indicates that stylistic impact, rather than fermentation performance, is likely to be more pertinent to the adoption of red wine aeration.