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Modified atmosphere packaging of ground pork

David M Gaebler, University of Nebraska - Lincoln


Modified atmosphere packaging (MAP) is being utilized extensively in European countries as a preservation technique for meat products. In the United States, large supermarkets are reducing or eliminating in-store meat departments and replacing them with prepackaged case-ready products shipped from a centralized processing facility. Fresh ground pork shoulder (SBLDR) and ground pork knuckles with sirloin fat trim (GS) were packaged in either 80:20 O2:CO 2(80/20) or 100% CO2(CO2) and held for 2 days (2DAY) or 8 days (8DAY) in unlighted storage (2°C) prior to lighted display for 8 days to determine differences in retail shelf-life due to these parameters. ^ A high level of carbon dioxide (CO2) was more effective in inhibiting microbial growth than a gas mixture of 80:20 O2:CO 2. During extended storage, (8DAY) in 100% CO2 inhibition of growth of aerobic microorganisms resulted in a 2 log reduction in aerobic plate counts (APC). During lighted storage, aerobic plate counts of ground GS and SHLDR packaged in CO2 were at least 1 log lower than when packaged in 80/20. ^ Increased storage time prior to retail display resulted in higher APC and psychrotropic plate counts. A half-log difference in bacterial counts (log10 c.f u./gram) resulted in a 6 day difference in product shelf-life as measured by aerobic bacterial plate counts for ground pork. Ground pork knuckles with sirloin trim in 80/20 had higher surface oxymyoglobin than ground pork shoulder, but ground pork shoulder displayed a more red color (higher a* values). After 8 days of lighted display, metmyoglobin reducing ability was still present and capable of keeping surface metmyoglobin levels below 40%, the point where customers reject red meat due to discoloration. ^ The findings reported in this dissertation support the use of pork knuckles with sirloin trim in MAP to produce a ground pork product of the highest quality. In situations were shipping times are lengthy and/or distances from the distribution center to retail display are long, an atmosphere of 100% CO2 is recommended to give product the longest possible shelf-life. ^ Oxidation of lipids is another important characteristic determining the shelf-life and quality of food products. Assays exist which measure malonaldehyde, a secondary product of lipid oxidation. Each assay has advantages and drawbacks which are unique to the specific assay. Disadvantages common to aqueous extraction and distillation techniques include creation of large quantities of spent chemicals, number of samples which can be analyzed in a single day, and the time necessary to evaluate the samples which have been processed. ^ Rapid distillation and extraction methods to quantify malonaldehyde were developed. These methods used microliter quantities of material, increased the quantity of samples evaluated and reduced the time necessary to process a large number of samples when compared to the original methods. ^

Subject Area

Agriculture, Food Science and Technology

Recommended Citation

Gaebler, David M, "Modified atmosphere packaging of ground pork" (1999). ETD collection for University of Nebraska - Lincoln. AAI9936755.