Pork chops were packaged in a controlled atmosphere (10% CO2/79% N2/1% O2, 30% CO2/68% N2/2% O2, 30% CO2/70% N2, 100% CO2 or air) and then stored at either 2 or 5 C. Changes in gas composition, microbiological counts and sensory quality were monitored after 0, 9, 12, 16, 19, 23, 30 and 37 days of storage. Two chops from each treatment were stored additionally under retail-like conditions for 3 and 5 days. The CO2 percent composition in the packages increased greatly during storage while O2 and N2 showed corresponding decreases. The most effective gas environment in extending sensory acceptability was 100% CO2. The best gas mixtures for extending shelf life at both 2 and 5 C were those containing only CO2 and N2. Sensory data indicated that odor became objectionable before the chops were rejected because of appearance. A temperature increase from 2 to 5 C resulted in greater increases in psychrotroph growth in the control environment (air) than in the CO2 - containing environments. Pseudomonas (oxidase-positive colony count) accounted for 25 – 60% of these counts. The inhibition of microbial growth in the CO2 - containing environments during controlled atmosphere storage appeared to carry over to the rewrap environment.
1Paper No. 11.333. Scientific Journal Series. Minnesota Agricultural Experiment Station, St. Paul, MN 55108.