The Impact of Micro-oxygenation in Tannat (2017)

This study examines the impact of micro-oxygenation in aging Tannat wine. Tannat wine was split into two identical tanks. The treatment tank was micro-oxygenated with a dosing stone through a Stavin Ox Box. Due to the small volume of wine, continuous micro-oxygenation was not possible, and instead a discontinuous regimen was put in place with a target oxygen rate of 5 mL Oxygen/L wine/month. This was achieved by dosing the wine with 0.61mL Oxygen/minute for approximately 10 hours every 3-5 days. Treatment was halted when malolactic conversion began. Chemistry results were not too different, except for sulfur dioxide binding (where more sulfur dioxide was binding in the control). Sulfides were not very different, and differences in Oenococcus are likely not due to the treatment. Color was not very different. The micro-ox wine had higher levels of anthocyanins, but slightly lower polymeric pigment and tannin. For the triangle test, of 27 people who answered, 5 people chose the correct wine (19%), suggesting that these wines were not significantly different. In fact, this suggests that judges consistently and significantly did not choose the correct wine and were biased to the replicates (p<0.05). In general, of people who answered correctly, 3 preferred the micro-ox wine, and 2 preferred the control wine. For the descriptive analysis, there were no strong trends for the descriptors used in this study. There may have been a slight tendency for the micro-ox wine to have higher Astringency, but this was very weak. These kinds of studies should be repeated in the future, over multiple varieties, utilizing both continuous and discontinuous micro-oxygenation schemes. Furthermore, more intensive micro-oxygenation regimens should be performed in future studies.

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Phenolic and Sensory Evolution of Wines from Oxygenation (2017)

This study examines the effect of oxygenation on wines. Cabernet Sauvignon grapes were harvested and, after completion of fermentation, wine was drained and pressed into two tanks. One tank was a control, and one tank received 40 mL Oxygen/L wine/month for 3 days, and this rate was then halved every 3 days until after malolactic conversion began, where it received micro-oxygenation at 0.5 mL Oxygen/L wine/month. A third set of grapes from the same block were picked 5 days later (after a large rain event), and then received flash détente. Since malolactic conversion completed so quickly for this treatment, its oxygenation could only be at 40mL Oxygen/L wine/month for three days after draining and pressing before switching to 0.5 mL Oxygen/L wine/month. The treatments between the control and oxygenated wines were similar, but the vinification of the flashed wine was different, marked by 10 days of fermentation (compared to 14 days for the other treatments, including a 3 day cold soak). The flashed wine also had slightly different additions made. No major differences are found in wine chemistry between the control and oxygenation treatment, except for slightly higher lactic acid in the treatment. The flashed wine had higher acidity, possibly due to differential tartrate adds. The oxygenated wine had higher rates of S. cerevisiae and several Lactobacillus species relative to the control, but lower acetic acid bacteria. The flashed wine had much lower levels of acetic acid bacteria and Lactobacillus, and lower levels of S. cerevisiae as well. However, it was higher in O. oeni. Color intensity lowered among the wines from November to April; however, the oxygenated wine may have had a slight increase in color intensity relative to the control over this time (although this was weak). The oxygenated treatment had higher color intensity than the control, and the flashed wine was highest. Phenolic parameters generally decreased from November to April, and oxygenation did not appear to have much effect on the phenolic parameters. The flashed wine was much higher in catechin and quercetin and was also higher in tannin. Although it was initially lower in anthocyanin (and higher in polymeric pigment), it ended up being higher in anthocyanin.

For the triangle test, of 26 people who answered, 12 people chose the correct wine (46%), suggesting that the wines were not significantly different. In general, people who answered correctly tended to prefer the oxygenated wine, although the preference trends were somewhat complex. For the descriptive analysis, there was a strong trend for the flashed wine to have higher overall aromatic intensity than the other wines (LSD=0.97). There was a slight trend for this wine to have higher Fruit Intensity and Body, and perhaps slightly lower Herbaceous/Green character (although it was similar to the oxygenated wine in this regard). The control wine tended to have higher Herbaceous/Green character, lower Overall Aromatic Intensity, and higher Astringency (although equal to Flash in this regard). The oxygenated treatment tended to have lower Bitterness and Astringency, and perhaps lower Body as well. More studies should be performed on oxygenation, with regard to timing, amount, and with regard to continuous vs discontinuous oxygenation.

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