Went to look this up and a suggestion for the search was "pineapple soften cervix," apparently pregnant women eat pineapple to attempt to soften the cervix for easier delivery...
What Sakuya says is correct, but her method is off. You need to blend the skin and fruit of the pineapple. Then you put that and your meat into a bag for no more than 45-minutes to an hour. For full reference, here is Guga of Guga Food/Sous Vide Everything doing a multi-hour demonstration: https://youtu.be/5X8KBX-LtAs
Why is this meat sandwiched between pineapple?It doesn't get hard even if you bake itOw ow ow...
My shoulders are stiff from reading all day...The enzymes in the pineapple help loosen and soften the fibers in the meat, making it more tenderOh, I see!