Gases in wines

Gases in wines

First of all, gases are naturally present in wine. Once pressed, for all wine’s movement, it will pick up oxygen(O2) and create Carbon dioxide (CO2) during fermentation.

Oxygen can be very beneficial to boost stunted fermentation, softening astringency, improve tannin, stabilizing color and get rid of some reduced smell. However, it can also be the cause of 3 types of oxidations : enzymatic, chemical, microbial. 

Enzymatic oxidation is produced by polyphenol oxidase and laccase. Both makes the SO2 unstable.

The second one is chemical and would react with phenol, change color (browning), losing aroma and bringing some reduced smell and taste

The last one is microbial oxidation and would feed bacterias, yeast and microorganism who can spoil the wine as acetic acid, acetaldehyde, ethyl acetate, etc

Those problems push to use Oxygen with care and moving or storing wine post fermentation with the minimum of contact with it. It is why (DO) has to be monitored frequently until the wine end up in a bottle. Using an electronical membrane sensor, a luminescent/optical sensorProbe or a luminescent with sensorspot allow you to check it. The big differences between those equipments would be speed, accuracies, if the probe have to be in contact with the wine or not, if it is fit in a bottle or just for tanks, and of course prices. Excess of O2 can be sparge with Nitrogen. Temperature is one of factor who has quite consequent importance with it. The wine will pick up more oxygen at cold temperature and releasing it better at hot temperature.

The second Gas mainly used is CO2. Depends of the characteristics of the wine, but it can enhance fruit flavor and bring some freshness to a white wine. However in red wines it can increase harsh textures and tastes in reds. So we impact on the style wanted, from somethings quite flat but with strong tanins to something fresh as sparkling wine. Sparkling wines have actually different methods. The gas can be 100% from the fermentation, directly the bottle (champagne style), or be manage in tanks with a pressure gas system, and sparge of one or different gases (Oxygen dioxide, nitrogen and/or argon). The level can be measured with a carbodosor and the excess can be remove by sparging Nitrogen or using a membrane contractor vacuum. Some factors have to be considering for the solubility (Temperature, alcohol, carbohydrates, phenols, proteins)

References:

NMIT powerpoint- oxigene management

https://winesvinesanalytics.com/features/article/119752/Strategies-to-Manage-Dissolved-Oxygen

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