Inhibition of melanosis and microbial growth in Pacific white shrimp (Litopenaeus vannamei) using high CO2 modified atmosphere packaging

Preserving quality of crustaceans requires efficient modified atmosphere packaging (MAP). Effects of CO2 (20%–80%) on quality and melanosis in chilled Pacific white shrimp (Litopenaeus vannamei) under O2 concentrations of 5 and 15% were investigated. Increased headspace CO2 and lipid oxidation contributed to loss of firmness due to protein degradation. Image analysis indicated increased degree of melanosis at higher O2 concentration. High CO2 above 60% and 5% O2 MAP effectively prevented melanosis (below 10% for 12 days) and formation of trimethylamine (TMA) concurrent with limited total viable count (TVC), Enterobacteriaceae and reduced conversion of pro-polyphenoloxidase into polyphenoloxidase accelerated shell browning. Linear correlation was found between TVC-melanosis and TVC-firmness for all MAP mixtures, while CO2 gave higher efficacy to inhibit melanosis at low O2 MAP. Increased CO2 linearly prevented melanosis and TMA formation, whereas decreased O2 concentration gave higher efficacy of CO2 indicated synergistic effects on melanosis and TMA inhibition.