Effect of early oxygen exposure on red wine colour and tannins

Impact of winemaking practices on the concentration and composition of tannins in red wine

“…In a more controlled environment, bubbling large volumes of air through active ferments in rotary fermenters has been shown to induce changes in tannins and astringency that are consistent with characteristics of aged wines (McRae et al 2014b). These oxygen-treated wines demonstrated similar tannin characteristics after 2 months of ageing to those of the control wines after 2 years of ageing, and the differences between the control and oxygen-treated wines were still significant after 2 years of bottle ageing (McRae et al 2014b). The oxygen-treated ferments contained a lower concentration of tannins, and the composition of tannins showed lower molecular mass and mass conversion yield.…”

“…Macrooxygenation normally occurs during primary fermentation during pump-overs although the amount of oxygen ingress can vary greatly depending on how the process is carried out (Moenne et al 2014). In a more controlled environment, bubbling large volumes of air through active ferments in rotary fermenters has been shown to induce changes in tannins and astringency that are consistent with characteristics of aged wines (McRae et al 2014b). These oxygen-treated wines demonstrated similar tannin characteristics after 2 months of ageing to those of the control wines after 2 years of ageing, and the differences between the control and oxygen-treated wines were still significant after 2 years of bottle ageing (McRae et al 2014b).…”

Use and impact of oxygen during winemaking

“…McRae et al (2015) described an experiment wherein a different concentration of oxygen (40% v/v oxygen in nitrogen, and air) was sparged through rotary fermenters twice in a 24-h period over 6 days; the composition of the phenolic substances was analysed at regular periods throughout the vinification and bottle-ageing process. McRae et al (2015) described an experiment wherein a different concentration of oxygen (40% v/v oxygen in nitrogen, and air) was sparged through rotary fermenters twice in a 24-h period over 6 days; the composition of the phenolic substances was analysed at regular periods throughout the vinification and bottle-ageing process.…”

“…A study of the addition of controlled doses of oxygen during the maceration phase in a closed system such as a rotary fermenter-in the which cap is gently broken up by rolling the whole fermentation vessel axially-allowed the effect of oxygen to be decoupled from the mechanics of skin extraction. McRae et al (2015) described an experiment wherein a different concentration of oxygen (40% v/v oxygen in nitrogen, and air) was sparged through rotary fermenters twice in a 24-h period over 6 days; the composition of the phenolic substances was analysed at regular periods throughout the vinification and bottle-ageing process. The oxygen-treated wines were significantly lower in anthocyanins than the control wines and were slightly higher in non-bleachable pigments.…”

“…There is little evidence in the literature that judicious use of oxygen during earlier stages of fermentation could perform a similar role. This has, however, recently been examined by Bekker et al (2015) who described further results from the experiment detailed in McRae et al (2015) where enriched air (40% oxygen v/v in nitrogen), sparged into rotary fermenters during the fermentation of Shiraz grapes, removed any reductive notes. After 3 days of treatment, the production of H2S was curtailed and no ethanethiol or ethylthioacetate was produced.…”