The feeling of burning the tongue after eating a large amount of pineapple is caused by a plant enzyme called bromelain. It is concentrated in the pineapple at the stem, which forms the middle hard part of the fruit. However, the area around the stem is usually eaten after the hard parts have been cut off. The burning sensation can be reduced or eliminated by cooking a pineapple or eating together with other meal. Concentrated pineapple juice is used as a meat tenderizer because bromelain breaks down protein.