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A Technical Guide for Wine Producers
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WHAT'S UP IN THE VINEYARD AND CELLAR
The prevention of oxygen uptake during bottling
The dissolved oxygen content in the bottle after bottling should ideally be less than 1 mg/l. Bearing in mind an uptake of 0.1 to 0.2 mg/l oxygen during the transfer of wine between tanks, it is obvious that the above-mentioned ideal scenario can only be achieved if the respective actions are executed with the greatest possible accuracy. All actions should be carefully monitored, because a few mistakes could spoil the entire operation.
If the bottling process is divided into the usual sequence of activities, the relevant actions to be initiated or applied may be summarised as follows:
Bottling tank
If bottling tanks are not filled to capacity, which is not supposed to happen, the space should be filled with inert gas. It will also be expedient to sparge inert gas through the wine even if the tanks are full. The use of argon or nitrogen as inert gases is recommended, in view of the fact that carbon dioxide is soluble in wine and may impart pétillance to the wine.
Wine hoses
The length of the hoses should be limited and any unnecessary coupling links avoided. Ensure that the hoses and coupling links are in good condition without any leakages. The hoses should prefereably be de-aerated with inert gas before the wine is racked.
Filter
Ensure that all filter connections have a tight seal and that air spaces are filled before wine is pumped through the filter.
Filling machine
Use vacuum filling machines if oxygen uptake during bottling has to be limited. Before the wine is pumped into the filling machine, oxygen pockets should be prevented by rinsing the filling machine with inert gas. The filling heights should be optimised and care taken that the desired filling heights are maintained in all bottles.
Pre-evacuation of the bottles
Bottles should be de-aerated with inert gas and a double evacuation of bottles with inert gas is even better.
Determination of oxygen in bottles
It is important to determine the oxygen levels in newly filled bottles to ensure that the preventative actions were successful.
Evacuation or rinsing of the filling space of bottles
Vacuum closure of bottles is beneficial provided its implementation is effective. The filling space should obviously be restricted to the minimum. Rinsing with inert gas apparently has limited advantages and the injection of liquid nitrogen is the most effective method.
Rinsing the closures
By rinsing the inside of hollow closures such as screw caps with inert gas before closure, oxygen uptake in the wine may be restricted.
Closed bottle
Once the bottling and closing processes have been completed, oxygen analyses of the wine and filling space should be conducted to determine the oxygen uptake.
Reference:
Crochiere, G.K. 2007. Practical Winemaking, January/February 2007: 74 - 84.
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