Shelf life of Merino lamb meat retail packaged under atmospheres of various compositions

The effect of four different gas mixtures on several characteristics of Merino fresh lamb meat quality was studied. Merino lamb meat was packed under four different atmospheres (Batch 1: Ambient air; Batch 2: 70% O₂ + 30% CO₂; Batch 3: 80% O₂ + 20% CO₂ and Batch 4: 30% CO₂ + 69.6% Ar + 0.4% CO) and stored in darkness and under refrigeration (3 ± 1 °C) for 12 days. pH values and weight losses of lamb meat showed no significant changes during 12 days storage (P > 0.05) and were not affected by the different used atmospheres (P > 0.05). Lightness (L*) was not significantly affected by gas atmospheres until day 12 of storage, lamb meat packed in contact with air (Batch 1) showing the lowest lightness (P < 0.001). Samples in contact with ambient air, presented the lowest a*‐values during most of the storage period (P < 0.001). Batch 4 (30% CO₂ + 69.6% Ar + 0.4% CO) showed the highest a*‐values after 7 days storage. Batches 2, 3 and 4 presented a lower microbial count of total aerobic bacteria and Enterobacteriaceae than batch 1 (P < 0.05), whereas for lactic acid bacteria counts there were not significant differences (P > 0.05).