Effect of Chamuang (Garcinia cowa Roxb.) leaf extract on inhibition of melanosis and quality changes of Pacific white shrimp during refrigerated storage

Inhibition of Pacific white shrimp polyphenoloxidase (PPO) with Chamuang leaf extract (CLE) was studied. CLE was rich in polyphenolic glycosides, in which chrysoeriol 6-C-glucoside-8-C-arabinopyranoside and 2-feruloyl-L-sinapoylgentiobiose were dominant. It also contained organic acids including hydroxycitric acid and oxalosuccinic acid. CLE with copper chelation activity could inhibit PPO in a dose dependent manner. Shrimp treated with 1% CLE had the lower melanosis score than 1.25% sodium metabisulfite (SMS) treated shrimp and the control throughout the refrigerated storage of 12 days at 4 °C (P < 0.05). Lower total volatile base (TVB) and thiobarbituric acid reactive substances (TBARS) were detected in shrimp treated with 1% CLE, compared to others (P < 0.05). Lower counts of mesophile, psychrophile, Pseudomonas, Enterobacteriaceae and H ₂ S-producing bacteria were obtained with 1% CLE treatment than the control and SMS treated sample during entire storage. Thus, soaking of shrimps in 1% CLE solution effectively reduced melanosis and quality deterioration.