Effect of CO2-N2 Atmospheres on the Microbial Flora of Pork

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Abstract
Pork loins were vacuum-packaged; one group remained vacuum-packaged, other vacuum packages were injected with gas atmospheres of either 20% CO2 + 80% N2 or 40% CO2 + 60% N2. Loins were stored for 7, 14, 21 and 28 days at 1–3 C. After each storage interval, chops were prepared from loins and subjected to 5 days of retail display. Psychrotrophic bacterial counts of lean and fat surfaces of loins stored in 40% CO2 + 60% N2 were frequently significantly lower than counts of comparable sites of vacuum-packaged loins. Lactobacillus counts of the subcutaneous fat cover of loins stored in CO2 + N2 were in most instances (7 of 8 comparisons) significantly higher than those of vacuum-packaged loins; this was true in only 2 of 8 comparisons for the lean surface. Psychrotrophic bacterial counts of chops prepared from loins subjected to the various storage treatments were seldom significantly different. During storage of pork loins, lactobacilli became a predominant part of the microflora and comprised more than 90% of the microflora after 21 days for loins stored in CO2 + N2 and after 28 days for vacuum-packaged loins. Pseudomonas spp. continued to persist to a greater degree in the vacuum-packaged loins than in the loins stored in CO2 + N2.