6.3.2 Transferring wine

Oxygen dissolution before and during bottling

In general, any operation that sets the wine in motion increases the oxygen dissolution and its consumption. It is more the start and finish of such operations that cause this dissolution (non-inerted vat space, hoses not inerted, etc.).

The final transfer of the wine from the main vat to the racking taps, and the vat used for bottling is no exception to the rule and causes additional dissolution of oxygen in the wine, which is very sensitive at this stage.

At the end of ageing, during bottling, the dissolved oxygen accumulated in the wine (or DO for Dissolved Oxygen) enables the calculation of the HSO (Head Space Oxygen) which represents the oxygen contained in the head space in order to obtain an optimal TPO (Total Packaged Oxygen) for the wine's storage once bottled.

This gives the following relationship: TPO = DO + HSO

Filling the vat used for bottling: good practices to reduce oxygen intake

Wine transfers from the supply vat to the racking vat can be accomplished using gravity when the configuration of the winery allows it.
Otherwise, a pump must be used. At this stage, exposure to oxygen must be kept to the minimum:

• Keep hose lengths and the number of connections to a minimum.

• Pump at a reduced speed at the beginning and end of the racking. At the beginning of racking a wine, the O2 input can be higher due to the air in the system, for example, in the pump, the pipes and the racking machine. At the end of the racking, there is the empty space in the racking vat which was progressively emptied during the filling. It is possible to inert the racking vat.

• Inert the hoses and the receiving vat prior to use with CO2/nitrogen/argon. For example, the hoses can be inerted with CO2, while the filling vat can have nitrogen bubbled into it. The vat can also be inerted with nitrogen or with a mixture of nitrogen and CO2.

• Fill the supply and drawing vats from the bottom.

• Avoid transferring wine at low temperatures: the lower the temperature, the more oxygen dissolves in wine.