The mean pH values for the samples packed under vacuum, 75% CO2 + 25% O2 and 100% CO2 throughout the storage period were 5.77 ± 0.08, 5.95 ± 0.08 and 5.86 ± 0.08, respectively. These values were slightly above the normal range (5.5 to 5.8) for lamb meat reported by Sobrinho, Purchas, Kadim, and Yamamoto (2005). A decrease in pH values over time was expected due to the increasing growth of lactic acid bacteria