Abstract
Microoxygenation (MOX) is used to improve wine colour and sensory quality; however, limited information is available for Pinot noir wines and wines with different initial phenolic content. In this study, MOX was applied to two Pinot noir wines, with either a low or a high phenolic content, at two doses (0.50 and 2.11 mg/L/day) for 14 days. With the sterile filtration applied, acetaldehyde formation during MOX was very low, supporting the influence of yeast on acetaldehyde production during MOX. The MOX dosage rate did not significantly affect colour development, while the Pinot noir wine with higher phenolics benefited more from MOX, significantly increasing colour intensity and SO2 resistant (polymeric) pigments. However, these changes did not guarantee colour stability, as a final SO2 addition (100 mg/L) largely erased the improvement to colour in all wines. This could be due to the lower acetaldehyde formation, thus less ethyl-bridged stable pigments resistant to SO2 bleaching. MOX also decreased the flavan-3-ols and anthocyanin monomers, which differed between the two Pinot noir wines, reflecting the initial phenolic content. Lastly, MOX generally increased the measured tannin concentration and affected the proportion of tannin subunits, with a decrease in tannin mass conversion and proportion of (-)-epigallocatechin extension units. Some of these changes in phenolic compounds could potentially increase astringency, suggesting that MOX should be applied to Pinot noir and other low phenolic wines with caution.
Highlights
Over the years, microoxygenation (MOX) has become a popular vinification technique to mimic barrel ageing and enhance wine sensory qualities
We have demonstrated that MOX applied to a young Pinot noir wine led to an increase in colour intensity and tannin concentration, and a higher oxygen dosage favoured the formation of polymeric pigments (Yang et al, 2021a; Yang et al, 2021b)
A greater impact on the tannin composition was observed with Pinot noir 1 (PN1), especially with the higher oxygen dosage, leading to a large decrease in the tannin yield (%) and (+)-catechin extension units, while increasing the proportion of terminal units
Summary
Microoxygenation (MOX) has become a popular vinification technique to mimic barrel ageing and enhance wine sensory qualities. It has been suggested that the oxidation of wines that have few free anthocyanins can lead to extensive tannin polymerisation, resulting in a dryness sensation (Boulton, 2001; Gómez-Plaza and Cano-López, 2011; Oberholster et al, 2015) This possibility to increase the astringency could be a cause for concern when applying MOX to Pinot noir wines. Cano-López et al (2008) reported that MOX applied to Monastrell wines with high initial phenolic contents, and high anthocyanin concentrations (i.e., approximately 450 to 550 mg/L), resulted in a greater formation of anthocyanin-derived pigments and colour intensity, along with a decrease in the mean degree of polymerisation (mDP) of tannins. The evolution of colour parameters, anthocyanins, polymeric pigments, monomeric phenolics and tannin composition are reported
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