A compound that helps digestion, papain is a common ingredient used in meat tenderizers. Papain also treats wool before dyeing and removes hair from hides before tanning. People also use papain to treat arthritis, ulcers, swelling and fever.
Papain appears in a few fruits, including kiwi and avocado. The fruit that contains the most papain is the papaya.
Female and hermaphrodite papaya trees produce cruder papain compared to male trees. Various papaya cultivars also produce different quantities of papain.
According to Cornell University, older papaya fruits contain more papain compared to younger fruits. However, the papain in younger fruit extracts is more active.