Nature of the inactivation by high hydrostatic pressure of natural contaminating microorganisms and inoculated Salmonella Typhimurium and E. coli O157:H7 on insect protein-based gel particles

This work studies and models microbial inactivation by high hydrostatic pressure applied to insect protein (Acheta domesticus) enriched gels. The target microbial groups and pathogens studied were total aerobic mesophilic (TAM) bacteria, molds and yeasts (M&Y), Salmonella Typhimurium and Escherichia coli O157:H7. Results indicated that high hydrostatic pressure reduced the microbial load of both, the natural contaminating microorganisms (TAM and M&Y) and the intentionally inoculated pathogenic microorganisms. However, inactivation of the initial microbial load was lower than 5-log reductions. Kinetic inactivation parameters were deduced by using the Weibull distribution function which presented high goodness of fit. Kinetic parameters of the model showed that the most resistant microbial group was total aerobic mesophilic bacteria, followed by E. coli O157:H7, mold and yeast and Salmonella with kinetic parameters of 2.21, 1.58, 1.27, and 0.17 (min × mL/CFU) at 350 MPa, respectively. Regarding the pathogenic microorganisms inoculated in insect protein gels, E. coli O157:H7 may be a good candidate Gram negative target microorganism for high hydrostatic pressure process development, because it usually contaminates these products and was the one with the highest baro-resistance. These reasons support that high-pressure treatments for this type of food should be designed considering this microorganism as a target.
The authors acknowledge the financial support of the projects AGL2013-48993-C2-2-R and AGL2017-86840-C2-2-R from the Spanish Ministry of Economy, Industry and Competiveness, FEDER funds.