Modern winemaking has discovered many different techniques and technologies to improve upon the quality of wine. One example is the use of micro-oxygenation during the red winemaking process. Simply put, micro-oxygenation of red wine allows a wine to be released to consumers at a young age while possessing characteristics of a wine that has been oak aged for many months.

Micro-oxygenation works by the addition of oxygen into red wine at a controlled rate and flow to stabilize color and improve astringency and aromatic components of the final wine. One difficulty with this technique is that each grape variety behaves differently when exposed to micro-oxygenation, thereby making it much more difficult to know exactly how much oxygen and how quickly the oxygen should be injected into the wine.

It is common knowledge among winemakers and other in the wine industry that adding oxygen affects those chemical and sensory components of a wine. General changes include changes to phenolics, sulfur compounds, and oxygen consumption. If the wine is exposed to too much oxygen, several problems can occur, including the oxygenation of phenolic compounds, increases in astringency, color, mouthfeel, and bacteria populations.

Finding the right amount of oxygen to add to red wine could have important quality and economic benefits for a winery, in that if the “right” amount of oxygen is added, wine quality would improve which would theoretically increase the consumer “liking” of the wine and ultimately increase consumer purchasing of said wine.

The goal of the study presented today was to determine how micro-oxygenation of red wine at different rates affects the sensory characteristics of the wine (specifically, Cabernet Sauvignon) and also how micro-oxygenation of Cabernet Sauvignon affects consumer preference.

Methods

Cabernet Sauvignon wine was made using grapes picked in 2007 from a vineyard in Mornington Peninsula in Australia. Micro-oxygenation was applied after alcoholic fermentation was complete but prior to starting malolactic fermentation.

Two 5000L stainless steel tanks were filled with wine, with one tank receiving a micro-oxygenation treatment of 25mL oxygen per liter per month and the other tank receiving a micro-oxygenation treatment of 50mL oxygen per liter per

month. One 500L stainless steel tank was filled with wine and used as the control (no micro-oxygenation treatment). After micro-oxygenation treatment, malolactic fermentation was allowed to commence in all wines.

Micro-oxygenation was completed using a “Microdue” device. In lieu of space, I will refrain from going into the details of how this device works, but if you’d like to know, just ask in the comments and I’d be happy to describe it there!

Wines were tested before and after micro-oxygenation treatment for standard enological parameters including: alcohol content, turbidity, pH, total acidity, volatile acidity, sulfur dioxide, color intensity, hue, degrees of red pigments, SO 2 -resistant pigments, total red pigments, and total polyphenols. All analyses were done in triplicate.

During the winemaking process, sensory analysis was performed by three winemakers.

After the winemaking process, wines were evaluated by 35 panelists: 30 of them (16 men and 14 women) were students studying winemaking and sensory evaluation at Charles Stuart University in New South Wales, Australia; 4 of them were winemakers; and 1 of them was a wine critic expert.

Each panelist received four wines: a control, two of the 25mL micro-oxygenation treatment, and one of the 50mL micro-oxygenation treatments. Panelists evaluated the wine for color, olfactory attributes, and mouth feel characteristics.

Wine was presented to the panelists in transparent glasses randomly and blindly.

Consumer preference tests were performed in the winery. Customers, visitors, and winery staff were recruited to participate in the consumer preference tests, for a total of 51 participants (21 men and 30 women between the ages of 21 and 60 years). According to the authors, none of the participants were “qualified wine tasters”. Wines were presented to the participants in the same manner as were presented to the panelists during the sensory analysis.

Results

Before Malolactic Fermentation:

At the beginning of the micro-oxygenation treatment, there were no chemical differences between the control wine and the treatment wines.

Throughout the micro-oxygenation process, color intensity significantly increased in both treatments compared with the untreated control.

Olfactory intensity and mouth feel complexity increased in micro-oxygenated wines compared with the control, and peaked after 3 days of treatment.

After 6 days of treatment, “reductiveness” and astringency decreased in micro-oxygenated wines compared with the control.

The 50mL treatment showed increased vegetal and bitterness character and decreased “reductiveness” and fruit freshness compared to the 25mL treatment.

After Malolactic Fermentation:

After micro-oxygenation treatments, pH, volatile acidity, and titratable acidity were similar between the treatment and the control wines.

Differences occurred in regards to color intensity, total red pigments, and total phenolics, which were all higher in control wines.

Wine hue was increased in micro-oxygenated wines. This suggests greater oxygen exposure on wine can have a browning effect on the red pigments (degree of red pigments was similar in all wines).

SO 2 -resistant pigments (those that improve color stability) increased in micro-oxygenated wines, and showed highest levels in the 50mL treatment. This confirms the idea that micro-oxygenation helps to stabilize wines.

-resistant pigments (those that improve color stability) increased in micro-oxygenated wines, and showed highest levels in the 50mL treatment.

Sensory Analysis:

There was a significant judge effect (i.e. certain judges scored markedly different than other judges), so calculations were performed to standardize the results.

There were significant differences in regards to sensory characteristics of all wines.

Fruit character was negatively correlated with higher scores, and was most prominently noted in the control wines.

The 50mL treatment was most noted for complexity and roundness on the palate.

The 25mL treatment was most noted for volume and fruit freshness.

Consumer Preference Analysis:

40% of participants preferred the 25mL micro-oxygenated wine treatment.

31% of participants preferred the 50mL micro-oxygenated wine treatment.

29% of participants preferred the control wine.

Participants most preferred those wines with high levels of complexity and roundness.

Participants least preferred those wines with high levels of flavor intensity, fruitiness, and fruit freshness.

Those characteristics that were seen positively to participants were most associated with micro-oxygenated wines, whereas those characteristics that were seen negatively to participants were most associated with control wines.

Overall consumer preference was ranked as: 1) 25mL micro-oxygenation treatment; 2) 50mL micro-oxygenation treatment; and 3) control wine.

The relationship between chemical parameters and consumer preference was statistically significant. This suggests consumer preference could be predicted based upon the chemical composition of any given wine (though take with a grain of salt, since only Australian Cabernet Sauvignon was tested).



Conclusions

According to the results of this study, the Cabernet Sauvignon wine treated with micro-oxygenation at a moderate level of 25mL per liter per month for 6 days was the most preferred wine for consumers at an Australian winery. Now, before every winemaker goes out and treats their red wine with 25mL per liter per month of oxygen for 6 days, one must understand that this micro-oxygenation treatment worked for the Australian Cabernet Sauvignon in this study, but may not work for any particular red wine. It is important to note that the chemistry is different for every red wine; thereby every red wine may be affected differently to the same micro-oxygenation treatment.

According to the authors, it is important that during the micro-oxygenation process, acetaldehyde, SO 2 , volatile acidity, temperature, and taste be monitored in order to determine how micro-oxygenation will be most effective for any one particular wine. It would be interesting and beneficial to see this study repeated using multiple types of red wines, however, it is still important to monitor the progress in any micro-oxygenation process, due to the many variations from batch to batch that may not have been controlled for in this or any similar experiment.

What is clear from this study is that short-term micro-oxygenation does improve the sensory characteristics of a wine, and also improve consumer preference of a red wine. The authors suggest that micro-oxygenation could be

a good alternative to oak aging if the winery wishes to release the wine to the public sooner than later. Note: I believe what they mean here in regards to oak aging is in relation to the TIME and not the actual complexity imparted by the oak into the wine. Ideally, they should have included an oak aging control to make this statement.

I would be interested in seeing this study repeated with more types of red wine, as well as a study examining more micro-oxygenation treatments. How much is too much? How little is not enough? It would be interesting to get an idea of a possible range to the benefit of micro-oxygenation, in order for winemakers to have a “zone” to hone in on during their own winemaking practices.

I’d love to hear what you all think! Please feel free to leave comments or questions!

Source: Parpinello, G.P., Plumejeau, F., Maury, C., and Versari, A. 2012. Effect of micro-oxygenation on sensory characteristics and consumer preference of Cabernet Sauvignon wine. Journal of the Science of Food and Agriculture 92: 1238-1244.