Grapes hanging on the plant do not ferment,but after being plucked from the plant,they can be fermented. Under what conditions do these grapes ferment? Is it a chemical or a physical change?

(N/A) Grapes attached to the plant are living,and their internal immune system and metabolic processes prevent fermentation.
Once plucked,the grapes are no longer connected to the parent plant's supply of nutrients and defense mechanisms.
Fermentation occurs when microbes (like yeast) act on the sugars present in the grapes under anaerobic conditions (absence of oxygen).
This process results in the formation of new substances like ethanol and carbon dioxide,which is a chemical change.