Enhanced process during aging Typical process during aging Press, settle and rack wine Macro aeration during primary fermentation, Venturi without backflow preventor Using oak during enhanced fermentation Enhanced process during red fermentation Typical process during red fermentation
Macro aeration during primary fermentation

. Winemakers generally underestimate, to a large extent, the amount of oxygen a red wine needs during fermentation.

2. Macro aeration helps maintain yeast viability and reduces the production of sulfides.

3. Macro aeration may play a role in the initiation of color stabilization.
Most red fermentations can use more, rather than less oxygen. This additional oxygen helps minimize production of H2S, which can lead to potential mercaptan problems later in the wine's life
  When implementing the venturi (see following, make a hole in the top of the pumpover system and attach a small nipple. Connect the nipple to a 3 to 6 foot air intake tube. This arrangement is the simplest passive method for putting air in intimate contact with fermenting must. Rack and returns, while effective at removing stems and green seeds, are not effective at aerating a fermentor. The out gassing of CO2 during the racking effectively blankets the wine and minimize contact with air.
  Other methods of putting air in contact with the must: opening a valve on the suction side of the pump, or using an active valve that opens when the pump is switched on, injecting compressed air or oxygen.

This type of venturi works under most conditions. When combined with the check valve, it can be used with most pumps and in a variety of positions. This system also provides excellent aeration when racking a tank off lees.
Learn more about Mazzei injectors (new window)

A venturi without a backflow preventor
This venturi system uses a nipple welded onto the 3 inch stainless pipe. Pascal Chatonnet at the University of Bordeaux first suggested its use to minimize sulfide production during fermentations. This system works well with a diaphragm air pump when it has a correctly matched irrigator.