If you would like to put pineapple in your jello, I have good news for you. You can actually combine the two and get a yummy dessert ... but you have to use canned pineapple to prepare it.

Jello contains gelatin (a protein, which is a processed version of collagen. Collagen is a material we have in our bones, for example). Jello also contains sugar, flavoring, and coloring agents. Like all protein, gelatin is made up of amino acids, the individual building blocks of live. Gelatin is insoluble in water, but individual amino acids are not, they are soluble. Pineapples, unlike most other fruit, contain an enzyme called bromelain, that breaks up the gelatin into it's amino acid building blocks. [Enzymes are biomolecules that catalyze chemical reactions; most of them are proteins themselves.] Due to the bromelain, your jello doesn't become (or stay) solid. If you add fresh or frozen pineapple to jello, soon they will just float in a soup of amino acids, sugar, flavoring, and coloring agents. BUT ... if you use canned pineapple, you can combine the two without a problem. During the canning process the pineapple gets heated and the bromelain breaks apart. Then the bromelain is no longer active and it canot attack the gelatin.