High hydrostatic pressure inactivation of Lactobacillus viridescens and its effects on ultrastructure of cells

The effect of high hydrostatic pressure treatment on Lactobacillus viridesc ens, a major spoilage micro-organism of processed meat, was investigated. W hen pressure was applied at 400. 500 and 600 MPa for 5 min, cell survival i n MRS broth was reduced approximately by 2, 7 and 8 log cycles, respectivel y. The combination of high pressure and temperature increase showed synergi stic effects on microbial inactivation. Empty cavities in the cell and DNA denaturation were observed after pressure treatment above 400 MPa. The leve l of microbial inactivation when Lb. viridescens was pressured in protein-f ortified MRS broth and ham were less than half compared with the inactivati on achieved in peptone water. Increasing the temperature during high-pressu re treatment solved these adverse effects in the ham.