Sterile quarter strength ringer s solution

From each sample, 10 g was added aseptically to 90 mL of sterile quarter strength Ringer’s solution (Lab M Limited, Lancashire, United Kingdom) in a stomacher bag (Seward Medical, London, UK) and homogenized in a stomacher device (Lab Blender 400, Seward Medical, London, UK) for 60 s at room temperature. For the enumeration of Total Viable Counts (TVC) and the dominant spoilage microorganism Pseudomonas spp., serial decimal dilutions were prepared in the same diluent and spread on the following media: a) tryptic glucose yeast agar (Plate Count Agar, Biolife, Milan, Italy) for TVC incubated at 25 °C for 72 h, and b) Pseudomonas Agar Base with selective supplement cephalothin-fucidin-cetrimide (LabM Limited, Lancashire, UK) for Pseudomonas spp., incubated at 25 °C for 48 h. After incubation, colonies were enumerated and microbial counts were logarithmically transformed (log CFU/g). Poultry samples with TVC counts exceeding 7.0 log CFU/g were considered spoiled as reported elsewhere [43 (link),44 (link),45 (link)].

A slice of 20 ​cm² (maximum thickness: 2 ​mm) from the surface of chicken breast fillet was removed aseptically using a sterile stainless steel cork borer (2.5 ​cm in diameter), scalpel and forceps, added to 100 ​mL of sterile quarter strength Ringer’s solution (Lab M Limited, Lancashire, United Kingdom) and homogenized in a Stomacher device (Lab Blender 400, Seward Medical, United Kingdom) for 120 ​s ​at room temperature. Serial decimal dilutions were prepared in the same medium and 1.0 or 0.1 ​mL of the appropriate dilutions were spread or poured on the following media: a) Tryptic glucose yeast agar (Plate Count Agar, Biolife, Milan, Italy) for the enumeration of Total Viable Counts (TVC) incubated at 25 ​°C for 72 ​h; b) Pseudomonas Agar Base with selective supplement cephalothin-fucidin-cetrimide (LabM Limited, Lancashire, United Kingdom) for the enumeration of Pseudomonas spp. after incubation at 25 ​°C for 48 ​h. After incubation, typical colonies for each microbial group were enumerated and colony counts were logarithmically transformed and expressed as log CFU/cm². Further on, the primary model of Baranyi and Roberts (1994) (link) was fitted to the growth data of TVC and Pseudomonas spp. to determine the kinetic parameters of microbial growth (maximum specific growth rate: μ_max; lag phase duration).

Samples (10 g) of ham slices were weighed aseptically, added to sterile quarter strength Ringer’s solution (LabM, Lancashire, UK) (90 mL), and homogenized in a stomacher (Stomacher 400, Circulator, Seward) for 60 s at room temperature. The resulting suspensions were serially diluted in the same diluent and 1 or 0.1 mL samples of the appropriate dilutions were poured or spread, respectively, on the following agar media: de Man–Rogosa–Sharp Agar (MRS, Oxoid, Hampshire, UK) for LAB, incubated at 30 °C for 72 h; Plate Count Agar (LabM, Lancashire, UK) for TVC, incubated at 30 °C for 48 h; STAA Agar Base (Oxoid, Hampshire, UK) for Brochothrix thermosphacta, incubated at 25 °C for 48 h; Rose Bengal Chloramphenicol Agar (LabM, Lancashire, UK) for yeasts/molds incubated at 25 °C for 5 days; Violet Red Bile Glucose Agar (Oxoid, Hampshire, UK) for Enterobacteriaceae, incubated at 37 °C for 24 h, Pseudomonas Agar Base (LabM, Lancashire, UK), for Pseudomonas spp. incubated at 25 °C for 48 h, as well as Palcam Agar Base (LabM, Lancashire, UK), for Listeria spp. incubated at 30 °C for 48 h.