Pineapple contains an enzyme that digests protein, causing a tingling sensation in the mouth.
Why it is true
Bromelain, present in pineapple, breaks down proteins on the tongue and cheeks. This is why the mouth can feel sore when eating fresh pineapple, and also why pineapple is an excellent meat tenderizer.
Source: Compound Interest
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.