Wine Grow Mold

Why Does Wine Grow Mold?

Don’t panic if you are reading this with a glass of wine in your hand. According to AWA mold inspections, It is sporadic for mold to infest bottled wine. It mostly occurs due to poor production methods and poor sanitation at the brewing stages. Contamination of wine during production can also cause mold infestation. Contaminants such as debris and dust encourage the growth of spores and bacteria.

With that said, you can continue sipping that wine and read below why wine might grow mold.

Causes of Mold Infestation in Wine

If mold grows in wine while fermenting, it is possible that the wine has been contaminated with mold spores more so during the early stages of winemaking. Fermentation of wine should strictly take place in a sterile environment free of contaminations. This prevents microbes such as molds and bacterium from infecting the wine and degrading its quality. Fermentation may produce alcohol, but the alcohol cannot kill the infestation of molds or other bacteria.


Improper sanitation of winemaking equipment causes a lot of mold problems. Winemakers should sterilize all equipment that comes into contact with the wine. These include bottles, airlocks, other utensils, siphon hoses, and fermenting equipment, both primary and secondary. You can use a metabisulfite sterilizing solution to clean the equipment.

It is also advisable to add sodium metabisulfite tablets or Campden tablets. This solution discourages the growth of microbes after racking the wine.


The wrong type of equipment can kill all your sanitation efforts and favor mold infestation. It is critical that proper equipment is used during all the stages of the winemaking process. Never use an open container to make wine. The wine should be isolated in an airtight fermentation vessel that prevents any infection from microbes. If this is not followed, chances of the wine having mold infestation can be very high.

The proper fermentation equipment should have an airlock system that contains a sulfite solution. The airlock should let the air out but prevent the air outside from getting in.

Flowers of Wine

This is more of an indication of contamination rather than a cause. Flowers of wine are described as yeast spoilage that forms white powdery blooms or white films over the surface of the wine. If you see the white film, it is evident that the wine has been contaminated.

Flowers of wine need oxygen to thrive, so if you see them in the fermentation vessel, it indicates that the airlock system might not be functioning properly. Fixing the airlock should solve the problem.

These are the main reasons why wine might grow mold. Mold growth usually occurs during the winemaking process and rarely during the bottling process. Contaminated wine is not bottled. All health, safety, and other quality standards are check-listed before that sweet wine is bottled for distribution. Bottled wine is air-tight, and therefore, the chances of contaminants that promote the growth of mold getting in the bottle are minimal. Knowing all this, you can continue enjoying that bottle of wine with no worries.

© 2021 Vinsurvin Sommelier Magazine .