How can the enzymes in fresh pineapple contribute to a tingly mouth?

Answer: They break down proteins on the mouth’s surface

They break down proteins on the mouth’s surface ✓ — Bromelain in fresh pineapple can break down surface proteins and contribute to irritation. That does not mean it digests your whole tongue, and acidity can contribute too. Heating reduces the enzyme’s activity, but does not remove all possible sources of irritation.

They release heat that burns the mouth lining — Bromelain does not cause a thermal burn by releasing heat. Its relevant action is protein breakdown; the fruit’s acidity can also contribute to irritation.

They turn dissolved sugar into sharp crystals — Pineapple’s enzymes do not create sharp sugar crystals in your mouth. Bromelain acts on proteins, not by turning dissolved sugar into an abrasive solid.