Controlled-Atmosphere Storage of Pork Under Carbon Dioxide

Fresh pork loin slices were packaged under three different anoxic atmospheres (100% N₂, 100% CO₂ and 50% N₂ + 50% CO₂) and kept at two storage temperatures (-1°C and 4°C) and two pressures (1.0 and 1.2 atm.) in reusable, gas impermeable metal boxes. A gas headspace to meat weight ratio of >31 per kg was maintained. Carbon dioxide concentrations were unchanged (controlled) during storage. Microbiological, biochemical and physical measurements were made during the 3-week storage period. While atmospheric pressure did not have a significant impact on shelf-life, samples stored at -1°C were satisfactory at 21 days in both CO₂ treatments. Samples under N₂ did not fare so well, showing higher levels of psychrotrophic bacteria after 18 days at -1°C and 14 days at 4°C. Samples kept in N₂ at 4°C were spoiled within 2 weeks. Bacterial growth was slowest under 100% CO₂, but samples stored under 50%-50% N₂-CO₂ at 4°C were also observed to be in good microbiological condition at 21 days of storage. Use of CO₂-containing atmospheres provided more than 7 extra days of shelf-life at 4°C over that attainable under 100% N₂. Shelf-life at -1°C was improved by 3 to 4 days over that at 4°C. Except for the length of time in storage, treatments had only a minor effect on pH, color, water holding capacity and shear force. These physicochemical characteristics were not factors which limited shelf-life.