The main role of bacteria is as a decomposer. The bacteria decompose the complex organic compounds into simple one which are reused in carbon cycle.

Why Wine Turns Sour

There are various factors that can contribute to the souring of wine, but one of the most significant reasons is the presence of aerobic bacteria.

Aerobic Bacteria and Wine

Aerobic bacteria require oxygen to survive and thrive. These bacteria are commonly found in the environment and can contaminate wine during the winemaking process or when the wine is exposed to air after bottling.

When aerobic bacteria come into contact with wine, they can consume sugars and other compounds present in the wine. As a byproduct of their metabolism, they produce acetic acid, which is responsible for the sour taste in wine.

How Aerobic Bacteria Contaminate Wine

Aerobic bacteria can enter the winemaking process through various means, including:

1. Grape Contamination: Grapes can carry aerobic bacteria on their skins. If proper sanitation measures are not implemented during the harvest and crushing of grapes, these bacteria can easily find their way into the wine.

2. Winery Equipment: Poorly sanitized winery equipment, such as fermentation tanks, barrels, and hoses, can harbor aerobic bacteria. If not properly cleaned, these bacteria can contaminate the wine during the winemaking process.

3. Oxygen Exposure: Wine that is exposed to air or oxygen after bottling is at risk of contamination by aerobic bacteria. This can happen if the cork is faulty or if the wine is stored in a container with a faulty seal.

4. Insufficient Sulfur Dioxide (SO2): Sulfur dioxide is commonly used as a preservative in winemaking to inhibit the growth of bacteria and other microorganisms. If a wine has insufficient levels of SO2, it may be more susceptible to contamination by aerobic bacteria.

Preventing Wine Souring

To prevent wine from turning sour due to aerobic bacteria, winemakers and wine enthusiasts can take several measures:

1. Sanitation: Maintaining proper sanitation practices throughout the winemaking process is crucial. This includes sanitizing equipment, storage containers, and surfaces to minimize the presence of bacteria.

2. Oxygen Control: Minimizing oxygen exposure during winemaking and bottling is essential. This can be achieved by using airtight containers, such as barrels or bottles with quality cork closures.

3. Sulfur Dioxide: Adding appropriate levels of sulfur dioxide to wine can help inhibit the growth of bacteria, including aerobic bacteria. This should be done in accordance with recommended guidelines and best practices.

By implementing these measures, winemakers can significantly reduce the risk of wine souring due to the presence of aerobic bacteria.

However, these bacteria need oxygen to grow. Wine's fermentation process is usually oxygen-free because of the large amount of carbon dioxide produced when yeasts turn sugars into alcohol. Uncorking the bottle introduces oxygen to feed thebacteria, and the flavor begins to change immediately.