Evaluation of oxygen content in commercial modified atmosphere packs (MAP) of processed cooked meats

Twenty-five packs of each of 13 processed cooked meats products, produced by three manufacturers, were analysed. Analysis was performed 1, 7, 14 and 21 days after obtaining samples at the point of manufacture. Although all products were packaged in modified atmospheres of 70% N₂ and 30% CO₂, oxygen was present in 88% of packs 24 h after packaging. Overall percentages of packs containing 0.0, 0.01-0.5, 0.51-1.2 and > 1.2% oxygen were 11.7, 38.4, 29.4 and 20.4%, respectively on day 1 and 0.0, 15.5, 5.3 and 79.3%, respectively, on day 21. Three comparable pork products produced by three different manufacturers contained different levels of oxygen on day 1. The high proportion of packages containing rejectably high levels of oxygen may pose a potential risk of product quality deterioration and reduced shelf-life of muscle-based foods. Results emphasize the necessity to monitor oxygen levels within packs of oxygen-sensitive foods, including processed, cooked muscle foods.