Alex was making wine using yeast. Alex found that if grape juice is kept with yeast in covered container, the yeast will slowly break down the glucose in the grapes. However, if the container does not contain any oxygen, the glucose is broken down more rapidly by the yeast, and the alcohol content increases very quickly. At the end of the experiment, Alex found that even though there are grapes that have not been oxidised, the breakdown rate becomes slower again.

1. Explain why the breakdown rate becomes slower again after some time.​