The Role of CO₂ Levels in High-Oxygen Modified Atmosphere Packaging on Microbial Communities of Chilled Goat Meat...

This study investigated the influence of CO₂ levels (20-40%: M20, M30, and M40) in high-oxygen modified atmosphere packaging (Hi-O₂ MAP) on microbial communities and quality attributes of chilled goat meat stored at 4 °C for 12 days. Alpha diversity indices (Chao1, ACE, Simpson, and Shannon) revealed a significant decline in microbial diversity over time, with storage duration exerting a greater impact than packaging conditions. Nonetheless, MAP played a crucial role in shaping microbial profiles, with air packaging (AP) showing the most distinct community, while M40 differed notably from M20 and M30, particularly by day 12, as shown by beta diversity analysis using principal coordinates analysis (PCoA). Proteobacteria and Firmicutes dominated microbial composition, with Pseudomonas and Brochothrix linked to spoilage in AP, while MAP, especially M40, favored the growth of Lactococcus, Acinetobacter, and Vagococcus, enhancing microbial stability. Despite pathogen levels remaining within safe limits, AP exceeded the spoilage threshold (TVC > 7.00 log colony-forming unit (CFU)/g), whereas all MAPs extended shelf life, with M40 most effectively suppressing microbial growth (p < 0.05). Interestingly, metagenomic functional profiling revealed that elevated CO₂ levels (>30%) altered metabolic pathways, shifting spoilage mechanisms from protein degradation in AP to carbohydrate metabolism in MAP, potentially influencing odor and texture attributes. MAP, particularly M40, also reduced protein and lipid degradation and oxidation, as indicated by lower total volatile base nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARSs), and shear force, suggesting better prevention of increased meat hardness and the development of undesirable odors and flavors, although high CO₂ negatively affected redness. Overall, M40 provided the greatest microbial stability and shelf life extension, highlighting the potential of optimized CO₂ levels in Hi-O₂ MAP to preserve goat meat quality and regulate spoilage dynamics.