Originally Posted by Andy M.
There is a component to the papaya juice, papain, that is the tenderizing agent. It is also present in pineapple and the commercial product Adolph's Meat Tenderizer.
Just splitting hairs here, so please don't take it personally. For Andy, you know that I hold your culinary knowledge in high regard. Papain is indeed found in papaya, and also, I believe in kiwi fruit. The tenderizing enzyme found in pineapple however, is bromelain. As you stated, Adolph's Meat tenderizer contains papain. McCormic's Meat Tenderizer uses bromelain.
An interesting fact about fresh pineapple is that the bromelain is powerful enough, along with the naturally occuring acids, to cause skin irritation and sometimes damage. People who work with raw pineapple must wear protective gloves. To much raw pineapple can cause your tongue to actually bleed.
I'm not sure about papain, but bromelain is denatured by heat, which is why you can use canned pineapple in jello, while fresh pineapple prevents it from setting up.
Seeeeeya; Goodweed of the North