2.5.2. Gas Composition and Microbiological Analysis

Each sampling day, the gas composition was measured with a portable O₂/CO₂ analyzer (Oxybaby, Carburos Metónicos, SA, Madrid, Spain).

Microbiological analysis was conducted as follows. Just after the pack was opened, 10 g of sample were placed in a stomacher bag with 90 mL of sterile peptone water (Scharlau, Barcelona, Spain) to obtain the 1:10 dilution. The sample was homogenized with a laboratory blender (PK 400 Masticator, IUL S.A., Barcelona, Spain) for 2 min, and then serial decimal dilutions were prepared in sterile peptone water. In duplicate, 1 mL or 0.1 mL samples of appropriate dilutions were placed onto selective agar plates. Total viable counts (TVC) were determined on a 3M Petrifilm Aerobic Count Plate which was incubated at 30 °C for 72 h. Enterobacteria were incubated on a 3M Petrifilm Enterobacteriaceae Count Plate at 37 °C for 24 h. Pseudomonas and Brochothrix thermosphacta were incubated on Pseudomonas Agar, with Cetrimide Fucidin and Cephaloridine supplement and streptomycin thallous acetate actidione agar (STAA, Oxoid, Spain) with STAA selective supplement, respectively, at 25 °C for 48 h. Lactic acid bacteria (LAB) were incubated on de Man, Rogosa and Sharpe agar at 30 °C for 72 h.