6890 gc gas chromatograph

This part of the work was aimed to study the effect of sub-lethal concentrations of ARGIRIUM-SUNCs on the bacteria metabolism. Thus, the strains showing the highest sensitiveness against ARGIRIUM-SUNCs (K. pneumoniae ECA 3-2) and highest resistance (E. roggenkampii ECA 4), were analyzed after exposure at 0.625 and 1.25 ppm. An 100 μL of a 24 h pre-culture of the strains (obtained as above described) were inoculated in 5 mL of TSB broth using vials of 20 mL. After closing hermetically the vials were incubated at 37 °C in dynamic conditions (100 rpm) up to 48 h. Six samples for each concentration and for each strain were prepared and non-inoculated vials containing only TSB were used as control. Three samples were analyzed each 24 h for the determination of volatile compounds (VOCs) following the methodology proposed by Ref.^{31 (link)}. An Agilent Hewlett Packard 6890 GC gas chromatograph equipped with a MS detector 5970 MSD (Hewlett Packard, Geneva, Switzerland) was used for peak separation and detection. A fused silica capillary column was a CP Wax 52 CB (50 m × 0·32 mm—Chrompack—Middelburg, the Netherlands), coated with polyethylene glycol (film thickness 1·2 μm) as stationary phase was used. The injector and FID temperature was 250 °C; detector temperature 220 °C; carrier gas (He) flow rate, 1 mL/min.

Volatile organic compounds of samples were analysed with gas chromatography-mass spectrometry coupled with solid-phase microextraction (SPME-GC-MS), using an Agilent Hewlett–Packard 6890 GC gas-chromatograph and a 5970 MSD MS detector (Hewlett–Packard, Geneva, Switzerland) equipped with a Varian (50 m × 0.32 mm × 1.2 μm) fused silica capillary column. Samples (3 g) were placed in 10 mL sterilized vials, added with a known amount of 4 methyl- 2-pentanol (Sigma-Aldrich, Steinheim, Germany) as internal standard, and sealed by PTFE/silicon septa. The samples were heated for 10 min at 45 °C and then a fused silica SPME fiber covered with 85 μm Carboxen/Polydimethylsiloxane (CAR/PDMS) (Supelco, Steinheim, Germany) was introduced into the headspace for 40 min. Adsorbed molecules were desorbed in the gas-chromatograph for 10 min. The conditions were the same reported by Montanari et al. [8 (link)]. Volatile peak identification was carried out by computer matching of mass spectral data with those of compounds contained in the libraries NIST 2005 and 2011. Data reported are the means of three different sausages.

Volatile organic compounds of samples were analyzed with gas chromatography-mass spectrometry coupled with solid-phase microextraction (SPME-GC‒MS) using an Agilent Hewlett–Packard 6890 GC gas chromatograph and a 5970 MSD MS detector (Hewlett–Packard, Geneva, Switzerland) equipped with a Varian (50 m × 0.32 mm × 1.2 μm) fused silica capillary column. Samples (3 g) were placed in 10 mL sterilized vials, added to a known amount of 4-methyl-2-pentanol (Sigma‒Aldrich, Steinheim, Germany) as an internal standard, and sealed by PTFE/silicon septa. The samples were heated for 10 min at 45 °C and then a fused silica SPME fiber covered with 85 μm Carboxen/Polydimethylsiloxane (CAR/PDMS) (Supelco, Steinheim, Germany) was introduced into the headspace for 40 min. Adsorbed molecules were desorbed in the gas chromatograph for 10 min. The conditions were the same as those reported by Montanari et al. [35 (link)]. Volatile peak identification was carried out by computer matching of mass spectral data with those of compounds contained in the libraries NIST 2005 and 2011. Data reported are means of three different burgers.