Even the finest wine becomes sour and unfit for consumption after a few days of being uncorked. Simply put, it turns into vinegar. Home winemakers are well aware of the souring problem, because it can spoil any wine (apple, grape, cherry, etc.). We’ll consider the reasons behind wine souring and talk about prophylactic measures which can save the beverage.
Wine turns into vinegar in case air has free entrance into the container. With enough oxygen and a temperature of 42-115°F (6-45°C) millions of acetic bacteria living in fermented wine material get active and start to process wine spirit into water and acetic acid. Depending on temperature, oxygen concentration and wine features souring process lasts from about 3-4 days to few weeks. Bacteria activity ceases when there’s almost no spirit left (wine vinegar contains less than 0.2% of it in the volume).
You can detect souring by smell and taste. At first wine will get a peculiar strong smell and sour taste. In a few days it will become sourer and less strong. That’s why you can’t keep a bottle of wine opened for too long, 2-3 days corked in a fridge max.
Both store bought and homemade wine can go sour during the process of manufacturing or while in storage. As a precautionary measure wineries add preservatives to their beverages, which stop bacteria from developing. The most popular preservatives are sulfites (salts of sulfuric acid). Sulphur prevents the developing of acetic acid in wine, but it is hazardous in large quantities.
A water seal helps keeping homemade wine away from airflow during the fermentation process. It’s a special device meant to hermetically seal the container and let carbon dioxide, which forms during the fermentation, to go outside. The matured wine is then bottled, hermetically sealed with corks, and stored at low temperatures.
Acetic acidification is one of the “incurable wine illnesses.” It means that it’s impossible to save wine, if it has turned into vinegar. In the early stages of souring (in the first few days) some winemakers try to stop acetic fermentation by pasteurization of homemade wine.
For this they heat up the bottled beverage to 140-150°F (60-65°C) and boil it for 20 minutes. But even a small amount of vinegar in wine can spoil its taste. Plus, you have no guarantee that pasteurization will prevent acidification. In most cases tainted wine gets thrown away or is kept as homemade wine vinegar.
In order to prepare vinegar any red or white wine will do, homemade is fine too. It’s enough to keep a glass (that’s important) bottle with wine opened for 2-3 weeks at a room temperature.