The normal range of bromelain specific activity is pH 4.5 to 9.8. According to relevant information, the most suitable pH value of F4 and F5 is 4.0 to 4.5, and F9 is close to neutral. The total extract of bromelain showed activity at pH 4.5 to 9.8. Bromelain, referred to as bromelain, also known as bromelain or bromelain enzyme, is a pure natural plant protease extracted from pineapple stems, leaves and skin, refined, purified, concentrated, enzyme immobilized and freeze-dried. .