The kinetic evaluation of the use of high hydrostatic pressure to destroy Lactobacilius plantarum and Lactobacillus brevis

The kinetics (D and z(p) values) of the high-pressure destruction of Lactobacillus plantarum and Lactobacillus brevis, isolated from traditional Greek salads, were determined. These two strains exhibited the highest pressure resistance of all bacteria and yeasts isolated from these products. Model suspensions of phosphate buffer (pH 7.0) or citrate buffer (pH 4.2) were used for high-pressure inactivation. The D values ranged from 11 to 1160 s in a neutral environment and a pressure range of 530-400 MPa, and from 1.5 to 560 s in an acidic environment with a pressure range of 530-270 MPa. A significant reduction in the pressure resistance was observed by lowering the pH of the suspension medium, especially as the pressure became greater. The effect of pressure change on D values was pH dependent. Values of z(p) of 70 and 80 MPa for L. plantarum and 71 and 100 MPa for L. brevis were obtained in neutral and acidic environments, respectively.