Question

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

Answer 1

Grapes hanging on the plants are living in nature. Their immune system does not allow any fermentation.
However, when these are plucked, they are no longer living. They undergo fermentation under aerobic conditions (in the absence of air or oxygen). The other factors which favour fermentation are enzyme and temperature between 25°C to 30°C. The fermentation is a chemical change.