Heat-induced Activation of Polyphenoloxidase in Western Rock Lobster (Panulirus cygnus) Hemolymph: Implications for Heat Processing

Polyphenoloxidase (PPO) activity in western rock lobster (WRL) hemolymph results in blackening, or melanosis, of the tissues after processing. The impact of processing temperatures on WRL PPO activity was evaluated under steady state and non-steady state temperature conditions. Baseline PPO activity and total PPO activity were determined spectrophotometrically. PPO activity showed a heat-induced net activation effect between 60 and 80 °C. Deactivation of the enzyme was not significant until temperatures reached 90 °C. During heating, a balance existed between heat-induced activation and deactivation of PPO. Therefore, maximization of PPO deactivation and minimization of melanosis formation in processed WRL would require the internal temperature of processed lobsters to exceed 90 °C.