Effect of pulsed electric field and modified atmospheric packaging on melanosis and quality of refrigerated Pacific white shrimp treated with leaf extract of Chamuang (Garcinia cowa Roxb.)

Pacific white shrimp treated with pulsed electric field (PEF) and subsequently soaked in 1% Chamuang leaf extract (CLE) were packed under various modified atmospheres (MAP) including absolute N-2, Ar or CO2. Lower melanosis score was evidenced in PEF pre-treated shrimp followed by soaking in 1% CLE and packing under CO2-MAP (PEF-CLE-CO2) than the control and other treated samples during storage at 4 degrees C (P < 0.05). PEF-CLE-CO2 showed lower pH, carbonyl content, total volatile base, peroxide value and thiobarbituric acid reactive substances but exhibited higher likeness scores (P < 0.05). Psychrophile, Enterobacteriaceae, Pseudomonas, lactic acid bacteria and H2S producing bacterial counts were less than 3 log CFU/g, which was lower than those of other samples at day 10 (P < 0.05). Oxidation of fatty acids (EPA and DHA) was prevented in PEF-CLE-CO2 than the control and other treated samples (P < 0.05). Volatile compounds in PEF-CLE-CO2 sample were negligible, compared to the control which was abundant in 3-methyl-1-butanol. Therefore, PEF and CLE treatment before MAP, especially under CO2 exhibited high efficacy in prolonging shelf-life of refrigerated shrimp.