Abstract
Fresh pork chops packaged in air, vacuum, and eleven modified gas atmospheres and stored at 4°C were studied to determine the influence of varying the concentrations of carbon dioxide and oxygen on the microbiological, physical and chemical characteristics of the chops. The concentrations of carbon dioxide and oxygen were in the range of 0 to 40%. The headspace gaseous composition changed over time as the concentration of the carbon dioxide increased while that of the oxygen decreased during storage. Increasing the carbon dioxide concentration delayed growth of aerobic psychrotrophic and mesophilic bacteria, and the Enterobacteriaceae, but slightly enhanced that of lactic acid bacteria. Increasing the oxygen concentration reduced growth of facultative anaerobic and anaerobic bacteria and enhanced that of Brochotrix thermosphacta. In general, carbon dioxide had more influence on the microbiological storage life of the chops than oxygen. Increasing the carbon dioxide concentration also reduced the redness of the chops, increased purge losses and promoted lipid oxidation, but retarded the formation of volatile basic nitrogen (VBN). Increasing oxygen concentration also increased lipid oxidation but generally there was no interactive effect of carbon dioxide and oxygen for all the parameters tested. Modified gas atmospheres with more than 10% carbon dioxide concentration were superior to air for extending the microbiological storage life of fresh pork chops. Gas mixture containing 20%C02 without oxygen was as effective as mixtures containing 40%C02 with or without oxygen in extending the storage life of fresh pork chops. Mixtures containing 40%C02 with or without oxygen had better performance than
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