Pineapple contains a kind of "pineapple enzyme", which can decompose protein. If eaten directly without soaking in salt water, this enzyme will stimulate the tender epidermis of oral mucosa and lips, making the mouth feel slightly stinging.
Salt can inhibit the activity of pineapple enzyme. Therefore, when eating fresh pineapple, it is best to soak it in salt water for a period of time, which can inhibit the stimulation of pineapple enzyme on our oral mucosa and lips, and at the same time enjoy the sweetness of pineapple.