Effects of Vacuum and Modified Atmosphere Packaging on Microbial Flora and Shelf-life of Pacific White Shrimp (Litopenaeus vannamei) during Controlled Freezing-point Storage at −0.8°C

Effects of vacuum and modified atmosphere packaging (MAP) on microbial flora, pH, total volatile basic nitrogen (TVB-N), trimethylamine (TMA-N), the exudates and sensory attributes in Pacific white shrimp (Litopenaeus vannamei) during controlled freezing-point storage at −0.8°C for a period of 14 days were investigated. The results indicated vacuum packaging (VP), 40%CO2/30%O2/30%N2 (MAP1) and 75%CO2/10%O2/15%N2 (MAP2) were more effective for inhibiting growth of Aeromonas spp., Pseudomonas spp., H2S-producing bacteria (including Shewanella putrefaciens) and Enterobacteriaceae and decreasing TVB-N and TMA-N contents as compared to air packaging (AP). pH values of VP and MAP2 samples were significantly (P < 0.05) lower than those of AP. Formation of exudates under AP, VP, MAP1 and MAP2 increased during the storage and the value was higher with the increase of CO2 levels. Sensory evaluation indicated that the shelf-life of fresh Pacific white shrimp got extended and reached 7 days under VP, 9 days under MAP1 and 11 – 12 days for the optimum MA-packaged under MAP2 as compared to 4 days' shelf-life under aerobic storage.