Microbial quality and lipid oxidation of Manchega breed suckling lamb meat: Effect of stunning method and modified atmosphere packaging

The effect of CO2 concentration and exposure time at stunning [80% CO2 for 90 s (G1); 90% CO2 for 90 s (G2); 90% CO2 for 60 s (G3); 80% CO2 for 60 s (G4)] plus an electrically stunned control group (G5) was assessed for lipid oxidation (LO) and microbial levels, [total viable counts, lactic acid bacteria, Enterobacteriaceae and Pseudomonas spp.] in Manchega breed suckling lamb meat at 24 h and 7 days post-mortem. Differences in LO were found at 7 days post-mortem (P < 0.05) with the highest value for G4. In general, values of all microorganisms studied were higher in G5.In addition the effects of these stunning methods (TS) on both LO and microbial counts were assessed in samples packed under two different types of modified atmospheres (MA: MA-A: 70% O2 + 30% CO2; MA-B: 69.3% N2 + 30% CO2 + 0.7% CO) at 7, 14 and 21 days post-packaging. Both factors (TS and MA), significantly affected LO, which was highest in the samples from the MA-A/G4 group. In general there were no significant differences in microbial quality between modified atmospheres. However, the type of stunning affected microbial count (P < 0.001) at all analysis times. In general, G4 and G5 showed the highest level in all microorganisms assessed, while the rest of the gas-stunning groups showed more stability with ageing.