Kidd antigens are resistent to the proteolytic enzymes papain and ficin.

Also inhibits some cysteine proteases such as caspase, papain, bromelain or ficin.

The researchers discovered that an enzyme called ficin, which is found in fig trees, appears to block the enzyme that causes browning.

Dr. Labuza said ficin was already used in meat tenderizers and to prevent the clouding of beer, but its role as a preservative had not been known.

Also, solutions of exogenous proteolytic enzymes (papain, bromelin or ficin) can be injected to augment the endogenous enzymes.