Changes in the microbiota and colour of pork meat batter during refrigerated storage in relation to the application of High Hydrostatic Pressure

The aim of this work was to study the effect of High Hydrostatic Pressures (HHP) on microbial degradation pattern and colour stability of pork meat batters used to produce fresh sausages. Besides treatments at 300 or 600 MPa for 5 min, pH (5.8 vs 5.4) and nitrite addition (100 vs. 0 mg/kg) were considered as variables. A not treated control was also monitored. The different samples were stored at 4°C and periodically analysed for their microbiota and colour. At the end of shelf life (TMC > 6.5 log CFU/g) a metagenomic analysis was also carried out to better clarify the effect of the treatments on microbial spoilage patterns. The results showed that the treatment at 300 MPa slightly affected initial cell load, but slowdown growth kinetics, especially at low pH, while 600 MPa strongly reduced microbial spoilage. The application of HHP was able to prolong shelf life of meat batters, from about two weeks (control) to 40 and 80 days in the case of treatments at 300 and 600 MPa, respectively. Metagenomic analysis revealed different degradation patterns in relation to tested variables: untreated samples showed the prevalence of Brochothrix spp., while the application of HHP determined the presence also of Carnobacterium, Bacillus, and Staphylococcus, depending on the treatment and the meat batter pH. Concerning colour, differences were mainly observed in redness (a*) and were due to the presence of nitrite. These findings suggest that HHP can be a feasible strategy to stabilize fresh sausages, although further studies are needed to assess their safety.