Effect of Gas Atmospheres on Microbial Quality of Pork

ABSTRACTS Ten 100 kg pigs were slaughtered, chilled at 2–3°C for 48 hr and divided at random into two equal groups. Strict sanitary procedures were used in removing loins. Loins from five pigs (expt 1) were vacuum packaged (50.8 cm Hg) in barrier bags, aged at 2–4°C for 5 days, cut into 1.27 cm thick chops and five chops were allotted at random to each treatment group from each animal. Experiment 2 loins were cut into 1.27 cm thick chops 2 days post‐slaughter and 5 chops were allotted at random to each treatment group from each animal. Storage treatments used were: 100% air, 100% O 2 , 100% N 2 , 100% CO 2 and a gas mixture (70% N 2 , 25% CO 2 , 5% O 2 ). Chops were individually packaged in saran bags which were evacuated, gas flushed, evacuated, partially filled again with gas and stored at −1.1°C. Bacteria (total count, lactic acid producers and anaerobes) were enumerated 7, 14, 21, 28 and 35 days post‐slaughter. No significant differences were found in bacterial counts between experiments within any sampling period; therefore, all animals were pooled into one experiment with 10 replications. Aerobic counts illcreased more rapidly and were higher (P < 0.05) for air, O 2 and N 2 samples at each week than for CO 2 and the gas mixture. The gas mixture and CO 2 suppressed growth of aerobes throughout storage. Aerobic counts were not suppressed by N 2 , and there was no significant difference in this count on chops incubated in air, O 2 and N 2 at any interval. No significant difference was noted in growth of lactic acid producers in the first 2 wk of storage; however, after the third week, counts were higher in CO 2 and the gas mixture treatments than in the air, N 2 or O 2 treatments. The fact that CO 2 and the gas mixture inhibited growth is of importance to the fresh meat industry and deserves further research.