Pineapple should work just as well as lemon. It's the acidification that prevents oxydation, and any acid will work.

Nor does it have to be all that strong. As little as a tablespoon of lemon juice in a quart of water will prevent fruit from darkening.

It may "work", but Pineapple contains a proteolytic enzyme bromelain, which digests food by breaking down protein. Pineapple juice can thus be used as a marinade and tenderizer for meat. The enzymes in pineapples can interfere with the preparation of some foods, such as jelly or other gelatin-based desserts.

"That" is not a simple protection from oxidation for the purpose intended.