Chemical element (O) whose Latin name Oxygenium is derived from the Greek "oxys" for "pointed, acidic". Actually, the name is wrong, because oxygen was previously held responsible for the formation of acids. That hydrogen is the cause of the acid character was only recognized later. At 21%, the colourless, odourless and tasteless gas forms the atmosphere together with nitrogen (78%) and carbon dioxide (0.04%). It is the main component in water and also contained in numerous compounds of the earth's crust. At around 50%, it is the most abundant element on earth. It is released during plant photosynthesis, in which sunlight, water and carbon dioxide are involved. Almost all animals and most plants need oxygen to live. In high concentrations, however, it is toxic to most living things. Oxygen is extremely reactive and combines very quickly with most substances.
During vinification it plays a decisive role either through aerobic (presence) or anaerobic (absence) action. Oxygen can have both positive (see under aeration) and negative (see under oxidation) effects on must and wine. At the beginning of fermentation, oxygen causes the yeasts to multiply. For this, the smallest amounts of oxygen are sufficient, which are dissolved from the must. Larger quantities are usually harmful. In various stages of winemaking, sulphur compounds and other substances are mainly used as oxidation inhibitors and preservatives. The carbon dioxide produced during fermentation protects against oxygen, but in the end oxidation must be prevented, otherwise vinegar or a spoiled, oxidised wine will inevitably be produced. This is best achieved by closed fermentation tanks made of stainless steel, whose empty space is filled with inert gas (protective gas) if necessary. As an alternative to this, a low and controlled contact with oxygen is deliberately permitted during reductive ageing.
During barrel finishing (i.e. in barrels made of wood), oxygen in small quantities is very important, as it contributes to the stabilisation of colour and taste and to natural clarification through the precipitation of unstable substances. This is especially true in red wine making, where some contact with oxygen is deliberately allowed during the tapping and refilling process. As an alternative or supplement, the so-called micro-oxygenation has been used since the beginning of the 1990s during winemaking. This is the dosed addition of oxygen to the must or wine. With certain types of wine, such as sherry or port wine, there is a deliberate contact with oxygen - i.e. oxidative ageing.
A frequently asked question is whether, and if so how much, the wine requires oxygen during bottle maturation, or what effect this has. According to studies this can be positive in the right amount especially for red wines with regard to aroma and colour. The next question is to what extent the various closures allow oxygen to enter the bottle. The ratio of the permeability of conventional screw top and cork (natural cork) is 1 to 3 or 4 - cork is therefore much more permeable. However, there are already alternative closures specially developed for this purpose, which allow controlled oxygen supply. Regarding various measures during vinification, please refer to oxygen management.