Favourable effects of soluble gas stabilisation and modified atmosphere for supressing regrowth of high pressure treated Listeria innocua

Bacteria can be injured or inactivated by high pressure processing (HPP), depending on the pressure level, holding time and bacterial strains and species. Fish soup was in this study treated with high pressure (400 and 600 MPa, 2 min) in combination with different packaging regimes; vacuum, modified atmosphere packaging (MAP), soluble gas stabilisation (SGS), and a combination of the two latter ones (SGS-MAP). The fish soup was before treatment inoculated with Listeria innocua, and stored at 5 °C and further analysed for a period up till 49 days. HPP gave a reduction of L. innocua of 3.5 and 7.3 log cfu/g immediately after exposure to 400 and 600 MPa, respectively. Both SGS and MAP showed a significant (P < 0.01) interaction with pressure. SGS in combination with pressure significantly (P < 0.001) inhibited the growth of L. innocua during storage. The same was observed when packaging in MAP (P < 0.001). Bacterial plating on non-selective and selective agar revealed that over 99.9% of the surviving cells after HPP treatment in combination with SGS or SGS-MAP were sublethally injured.