Question

Pineapple contains a protease enzyme that breaks down proteins. If you try to make a jelly with fresh chunks of pineapple, the jelly won't set but it would set if you use canned pineapple.

Answer 1

Fresh pineapple contain enzymes which breaks down protein molecules in liquid that would turn into jelly, making them smaller, so they can't tangle up, which stops the jelly setting.

In canned pineapple, due to a change in temperature, the protease enzyme becomes inactivated, and hence it won't break protein molecules of the liquid, allowing them to tangle.