The display life of retail packaged pork chops after their storage in master packs under atmospheres of N(2), CO(2) or O(2) + CO(2)

Commercial, bone-in pork loins were divided into four portions. One portion of each loin was vacuum packaged, then stored at -1.5 °C. The other portions were each divided into three chops, which were retail packaged. The retail packs were master packaged under atmospheres of N(2), CO(2) or O(2) + CO(2) (2:1, v/v), then stored at 2 °C. The pork was assessed after storage for up to 42 days. At each assessment, a vacuum pack and a master pack of each type, each containing product from the same loin, were withdrawn from storage. The vacuum packaged portion was cut into three chops, which were retail packaged. The chops from all packagings were displayed in a retail cabinet which maintained average air temperatures between 3 and 6 °C. The chops were assessed twice daily until they were judged to be of undesirable appearance. After storage for 1 or 2 days, the chops from all master packs appeared less desirable than the freshly cut chops. After all longer storage times, chops from N(2) and CO(2) atmospheres appeared as desirable as freshly cut chops, as did chops from O(2) + CO(2) that were stored for up to 16 days. However, chops stored under O(2) + CO(2) for 21 days appeared undesirable. Chops stored under N(2) or O(2) + CO(2) developed spoilage odours, after storage for 28 or 21 days, respectively. Bacteria were more numerous on the fat than on the muscle tissue. The numbers of bacteria were 10(7) cfu cm(-2) on the fat surfaces of chops stored under vacuum or N(2) for 42 days. The numbers of bacteria were 10(6) cfu cm(-2) on the fat surfaces of chops stored under CO(2) for 42 days or under O(2) + CO(2) for 21 days. At those times, only lactobacilli were isolated from chops stored under CO(2), but small or large fractions of enterobacteria were present in the flora on chops stored under vacuum or N(2), respectively, while the flora on chops stored under O(2) + CO(2) contained large fractions of Brochothrix thermosphacta and Gram negative, strictly aerobic, spoilage bacteria. After all storage times, chops cut from vacuum packaged portions remained of desirable appearance when displayed for 48 hr or longer. Chops stored under N(2) or CO(2) for between 2 and 35 days, or under O(2) + CO(2) for between 4 and 12 days, retained a desirable appearance during display for the same times as the freshly cut chops. Off-odours were apparent in chops after their display following storage under vacuum or CO(2) for 21 days, or under N(2) or O(2) + CO(2) for 12 days. The numbers of bacteria on the fat surfaces of chops spoiled by off-odours were ≥ 10(5) cfu cm(-2). The flora on chops removed from display were generally enriched for B. thermosphacta, enterobacteria and/or Gram negative aerobes as compared with the flora on the chops when they were removed from the storage packs. Those data indicate that the storage life of master packaged, display ready pork will probably be severely limited by the poor hygienic condition of commercial products, to little more than 1 week for product stored under N(2) or O(2) + CO(2) or < 3 weeks for product stored under CO(2).