When to Aerate A Wine

At what point do you aerate your fruit wine?
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Jason,
Aeration should only be done during the primary fermentation. This is the first 3 to 5 days of when the wine is in a primary fermenter and most active.
The only reason aeration is done is to give the wine yeast more ability to multiply and establish a solid colony. When a packet of wine yeast is put into a 5 or 6 gallon batch of wine, it has the monumental task of growing itself 100 to 200 times that little packet. That’s what causes all the beige-colored sediment you at the bottom of a fermenter. To readily do this the wine yeast need air. Without the air the colony size may suffer resulting in a sluggish fermentation.
Ironically, after the yeast colony is well established and the fermentation is starting to slow down, air is the enemy. For the rest of the wine’s life you want to keep air exposure time short and splashing to a minimum. The major concern here being oxidation of the wine.
What all this means for the home winemaker who is making 5 or 10 gallons is that the primary fermenter should be left exposed to air. This can mean doing something as simple as leaving the lid completely off a bucket fermenter. Cover it with a thin tea towel, nothing more. Or for a winery dealing with 500 gallon vats, this could mean continuously pumping and recirculating the wine back out on top the fermentation surface, much like a fountain.
There is a second element to this as well. Regardless of how much you are fermenting, you will always want to make an effort to keep a dried cap from forming on the surface of the fermentation. The pulp will want to rise during a primary fermentation. If left undisturbed it can dry and form a solid cap, choking the wine yeast off from the much needed air.
To prevent this from happening you will want to punch the cap back down into the wine. For most home winemakers with their 5 and 10 gallon batches, once a day is plenty. You can use something as simple as a potato masher for this purpose or you can stir it until the cap is dispersed. For larger batches you may need to punch down the cap several times a day.
Hope this information helps you out.
Happy Winemaking,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.