The inactivation and damage of histamine-forming bacteria (HFB), Enterobacter aerogenes and Staphylococcus capitis, in a 0.1 M potassium phosphate buffer (pH 6.8) and marlin meat slurry by high hydrostatic pressure (HHP) treatments were studied using viability measurement and scanning electron microscopy (SEM). HHP treatments showed first order destruction kinetics to E. aerogenes and S. capitis during the pressure holding period. HFB in marlin meat slurry had higher D values and were more resistant to HHP treatments than in phosphate buffer. In phosphate buffer, E. aerogenes had higher D values than S. capitis at >380 MPa of pressure, whereas the reverse trend was noticed at lower pressures (<380 MPa). In marlin meat slurry, S. capitis had a higher D value than E. aerogenes at the same treatment pressure, indicating that S. capitis was more resistant to HHP treatment. To our knowledge, this is the first report to demonstrate that HHP can be used to inactivate HFB, E. aerogenes, and S. capitis, by causing disruption to bacterial cell membrane and cell wall as demonstrated by SEM micrographs.
Keywords: SEM; high hydrostatic pressure; histamine-forming bacteria; inactivation.