Effect of ultra-high hydrostatic pressure on the survival of Chromohalobacter beijerinckii

The aim of the study was to determine the effect of ultra-high hydrostatic pressure on the survival of Chromohalobacter beijerinckii in samples of nutrient broth containing a 6% addition of NaCl and in samples of cold-smoked salmon. Both types of samples were exposed to ultra-high hydrostatic pressure of 300 and 400 MPa for 0, 5, 10 and 15 min. The number of Chromohalobacter beijerinckii was determined in all control samples and samples subjected to high pressure. The total number of aerobic bacteria was additionally determined in the samples of cold-smoked salmon intentionally inoculated with Chromohalobacter beijerinckii. It was found that Chromohalobacter beijerinckii showed a clearly greater sensitivity to high hydrostatic pressure in the nutrient broth (D-values: 300 MPa - 3.72 min; 400 MPa - 1.90 min) than it did in the samples of cold-smoked salmon (D-values: 300 MPa - 5.83 min; 400 MPa - 3.08 min). The results concerning the total number of aerobic bacteria show that Chromohalobacter beijerinckii is more susceptible to high pressure than the accompanying microflora present in cold-smoked salmon. High pressure treatment at 400 MPa applied for 15 min caused a destruction of Chromohalobacter beijerinckii cells that was clearly visible under a scanning electron microscope. Chromohalobacter beijerinckii belongs to bacteria that have average sensitivity to high hydrostatic pressure.