Inhibition of melanosis formation in Pacific white shrimp by the extract of lead (Leucaena leucocephala) seed.

Lead (Leucaena leucocephala) seed extract was prepared using distilled water as a medium. An extraction yield of 26.16g/100g of seed was obtained after extraction at room temperature for 12h. Total phenolic and mimosine contents in the lead seed extract powder (LSEP) were 17.4g GAE/100g and 8.8g/100g, respectively. LSEP at different concentrations (0.05%, 0.1%, 0.25%, 0.5%, and 1%, w/v) showed inhibitory activity towards polyphenoloxidase (PPO) of Pacific white shrimp in a dose dependent manner. When the whole Pacific white shrimp were treated with 0.25% and 0.5% (w/v) LSEP, the shrimp treated with 0.5% LSEP had the lower melanosis score throughout the storage of 12days and showed a higher score for colour and odour, as well as overall likeness, compared with the control (without treatment) and 1.25% sodium metabisulphite treated samples at day 12 (P<0.05). Meat of shrimps treated with LSEP at both levels had the increase in mimosine content up to 8days, suggesting the migration of mimosine into shrimp muscle during extended storage. Therefore, 0.5% LSEP can be used as a novel melanosis inhibitor for Pacific white shrimp.