Can Grapes Ferment on the Vine?- All You Need to Know

You mean unpicked grapes to ferment? A good percentage of the global population knows that for the grapes to ferment, you must pick them from the vine. However, what if you delay picking them from the vine? Can grapes ferment on the vine?

Well, we are here to answer such questions, count yourself lucky if you are reading this article. At the end of this paper, you should be able to know everything that may happen when grapes start to ferment. For fence watchers, grapes will ferment only when you pick them from the vine.

Continue to read the entire content to know why grapes won’t ferment while still on the farm. They ferment after you pick them from the oxygen source i.e., the vine itself. The protective barrier in their skin breaks when they are off the vine.  Continue reading for detailed information.

Why Do Grapes Ferment When Off the vine?

Why Do Grapes Ferment When Off the vine

Fermentation is a process that majorly depends on the presence of oxygen and yeast. Yeast particles tend to hang around in the atmosphere, meaning that they can land on the grapes. This implies that if the skin of the grapes is healthy enough, the yeast won’t be able to find its way in; no fermentation process will take place.

Furthermore, when you pluck, they will suffer from insufficient oxygen on their cells. The anaerobic condition will be experienced, triggering the process of fermentation. If you have decided to make your wine at home this festive season, the fermentation process can be fastened by addition of yeast to your crushed grapes.

Grapes contain high levels of sugar that will be converted to alcohol in the presence of yeast. During the fermentation process, yeast tends to develop an excellent wine taste. Another reason why yeast is advantageous is that it’s responsible for developing the body of the wine. This is therefore a determinant factor on how heavy or lighter wine should taste when you drink.

The level of yeast will be lowered when the level of alcohol rises in your grapes. The reason behind this statement is that yeast rarely survives in an alcoholic environment. This means that the yeast will not have any effect on the grapes when the level of alcohol is okay.

Yes, this also means that the fermentation process is over; go on and have a taste of your homemade wine. 

Can grapes ferment on the vine?

can grapes ferment on the vine

After having a clue on why grapes ferment when plucked from the vine, let’s now look at if it’s possible for these fruits to ferment on the vine. Like any fruit, grapes require a special environment to ferment. What I mean is that there are some considerations that should be kept into place.

For instance, the environment should favor bacterial growth to enhance fermentation. Unplucked grapes tend to have robust skin, responsible for protecting it from mold and bacteria. Additionally, these fruits contain sufficient oxygen while on the vine. Therefore, it’s not possible for them to ferment under such conditions; no fermentation will take place.

If you don’t pluck the grapes, as days go by, their skill will become weak, paving way for bacteria and mold to penetrate. In such situations, the grapes will end up fermenting naturally; though this happens rarely. Over time, unpicked grapes will fall on the ground and birds or insects will have found something to put a smile on their faces. They will celebrate!

While on the ground, the chances to ferment on their own are still minimal. And this occurs mostly when the skin of the grapes are broken, allowing yeast to get access to the internal cells. The yeast will work on the sugars available in the grape. The chances of having a fermentation process in such a condition are still questionable because the oxygen is available but no sufficient yeast to consume sugars.

Occasionally if the environment is cold, no fermentation process will take place.

From this discussion, the grapes will only ferment in an environment with less oxygen supply. The fermentation process is chemical and involves the following stages;

Aerobic oxidations

Aerobic oxidations

While on the vine, the grapes are still alive, meaning that they depend on photosynthesis to manufacture food. They achieve this by converting the atmospheric CO2 to oxygen and glucose. The excess glucose will be then stored in the form of starch and whenever the plant is running low on energy, it will reconvert the starch to glucose.

The existence of enzymes in the plant mitochondria is purposeful as they utilize oxygen to transform the glucose to water and CO2. This process is what we refer to as the aerobic oxidation or respiration.

Anaerobic oxidation

After unplucking and storing grapes, there will be insufficient oxygen. Therefore, the grapes will have to opt for an alternative method to generate energy. To alcohol, fermentation is two pathways known as anaerobic oxidation.

You might be interested to read also our another comprehensive article of: Can You Second Ferment Kombucha in Plastic


  • Do grapes contain large amounts of alcohol?

Grapes don’t have alcohol. But, if they undergo fermentation, you are likely to have alcohol. The process of fermentation hasn’t started yet in fresh grapes; the level of alcohol is low. There is no need to worry about eating your fresh grapes with the fear of getting drunk.

  • What are some of the uses of fermented grapes?

Fermented grapes are advantageous to many manufacturers since they are used to produce wine. You should therefore avoid consuming raisin-like grapes; you can get sick.

Final words

I don’t know if you have ever come across drunkard animals? For my case, this is possible since they can consume grapes crushed on the ground. The skin of such grapes is not robust enough to prevent the penetration of yeast in the cells. Well, this means that fermentation rarely occurs on unplucked grapes.

At least you can now argue with your folks on the “can grapes ferment on the vine” question. For your information, grapes like any fruit do require a special environment to ferment; not in the tree because oxygen supply is sufficient.