A fruit that eats you back
Why Does a Pineapple Sting Your Mouth?
Fresh pineapple makes your tongue tingle because it contains an enzyme that starts digesting you.
-
Step 1 of 5
The enzyme takes proteins apart.
Pineapple contains a substance whose whole job is cutting proteins into pieces. Your tongue and the inside of your cheeks are made of protein.
-
Step 2 of 5
Which is why it stings and not much else does.
The raw feeling is not acid, though pineapple is acidic too. It is the surface of your mouth being very slightly broken down, and then repaired.
-
Step 3 of 5
Heat destroys it completely.
Enzymes are proteins themselves, and heat wrecks their shape. Tinned or cooked pineapple never stings, because the enzyme was destroyed before it reached you.
-
Step 4 of 5
It is used deliberately in cooking.
The same enzyme tenderises meat, which is why pineapple juice turns up in marinades — and why fresh pineapple stops a jelly setting.
-
Step 5 of 5
The fruit is many fruits fused together.
A pineapple is not one fruit with a pattern. It is a hundred fruits stuck together. Each diamond on the outside was a separate flower with its own small fruit. They grow together into one mass, which is why the surface is patterned like that.
Pineapple plants take two or three years to make one fruit, and the plant grows on the ground rather than on a tree.
The short version
Fresh pineapple carries a protein-splitting enzyme that nicks the surface of your mouth, and cooking destroys it.
Try it yourself
Try setting a jelly with fresh pineapple and with tinned. Only one of them sets.