Apai 10u

PGFE was applied for typing the Lb. plantarum T571 strain and Lb. monocytogenes strains, according to Doulgeraki et al. (2010) (link) and Kostaki et al. (2012) (link), respectively. All isolates were digested with the restriction enzyme ApaI (10U) (New England Biolabs, Ipswich, MA, United States) according to the manufacturer’s recommendations for 16 h. Restriction fragments were separated in 1% PFGE grade agarose gel (Bio-Rad, Hercules, CA, United States) in 0.5-mM Tris–borate buffer on CHEF-DRIII (Bio-Rad, Hercules, CA, United States) equipment with running parameters as described at Papadopoulou et al. (2018) (link). The obtained restriction profiles were compared with the PFGE fingerprints of the inoculated Lb. monocytogenes strains and Lb. plantarum T571 strain.

Ham slices were analyzed at specific time intervals during their storage at the different temperatures and from all the cases tested (with or without HPP treatment, with or without edible films (either OEOF or OEOS). From specific time points, approximately 20% of the colonies were randomly collected from the appropriate dilution on Palcam agar base or ALOA, after the enrichment step. The isolates, after checked for their purity, were stored in −80 °C in BHI broth, supplemented with 20% (v/v) glycerol. Before further analysis, each isolate was grown twice in BHI broth at 37 °C for 24 h.
For Listeria monocytogenes typing, pulsed field gel electrophoresis (PFGE) was used according to Kagkli et al. [51 (link)]. The restriction enzyme ApaI (10U) (New England Biolabs, Ipswich, MA, USA) was used in line with the recommendations from the manufacturer for 18 h. After the digestion step, restriction fragments were separated in 1% PFGE grade agarose gel in 0.5 mM Tris-Borate buffer on a CHEF-DRIII (BIO-RAD, Hercules, CA, USA) equipment with the following running parameters: 6 V cm⁻¹, 1 s initial switching time, 40 s final switching time and 18 h total run at 14 °C. The obtained restriction profiles were then compared to the PFGE fingerprints of the inoculated Listeria strains.