A dissolving CO2 headspace combined with organic acids prolongs the shelf-life of fresh pork

The aim of this paper was to evaluate the effect of a novel CO2 packaging method in combination with organic acids on the microbial growth in fresh pork meat. Fresh pork fillet was packed with a small amount of 100% CO2 (initial gas/product ratio 0.2/1.0) and a brine solution containing citric acid (3% w/w, pH 5), acetic acid (1% w/w, pH 5) or a combination of both. Microbial counts and composition in the product were determined. CO2, citric acid and acetic acid each reduced total growth after four weeks of storage and delayed the onset of microbial growth. Combinations of treatments increased the effects and microbial growth in samples packed with a combination of CO2 and both acids was negligible even after 35 days. However, the addition of citric acid to the packages led to significant precipitation in the brine. Analysis of the bacterial flora showed that lactic-acid bacteria dominated the flora in samples packed with CO2 while vacuum-packed samples contained high numbers of Pseudomonas sp. and yeast. As all CO2 dissolved in the product within hours after packaging, the outer appearance of the package was that of a vacuum-package. As a result, this novel packaging method combined the advantages of modified atmosphere packaging (antimicrobial effect of CO2) and vacuum packaging (low space requirement).