Combined Effects of Gas Composition in Modified Atmosphere Packaging and Chitooligosaccharide-EGCG on Quality Changes in Refrigerated Asian Hard Clam Meat

The influence of different gas compositions in modified atmospheric packaging (MAP) without and with chitooligosaccharide-EGCG (CE) conjugate on storage stability of Asian hard clam (HC) meat during storage at 4 °C was studied. Microbial load of HC meat was <5 log CFU/g when packaged under MAP, regardless of treatment, up to 18 days of storage, whereas control exceeded viable bacterial count (6 log CFU/g) on day 9. The lowest microbial load, volatile bases, and lipid oxidation were obtained in HC meat pretreated with 600 ppm of CE conjugate and MAP (80% CO₂/20% O₂) (MAP4-CE) (p < 0.05). Correlation heatmap analysis showed that a high-CO₂/low-O₂ atmosphere was the primary determinant of reduced Pseudomonas growth and lipid oxidation in HC meat, whereas the CE conjugate conferred only minor oxidation and nitrogenous spoilage indices. HC packed under MAP exhibited higher cooking and drip loss, along with increased toughness and firmness, irrespective of treatment. PUFA of MAP4-CE was retained during 18 days of storage. High-CO₂, with or without CE, redirected the microbial diversity toward CO₂-tolerant taxa. Overall, MAP4-CE had an extended shelf-life of at least 18 days while better preserving lipid quality and delayed growth of spoilage bacteria.