Synergetic Effect of Elevated Hydrostatic Pressure, Mild Heat, and Carvacrol on Inactivation of Nontyphoidal Serovars in Buffered Environment.

A four-strain mixture of nontyphoidal and a strain of Tennessee were exposed to elevated hydrostatic pressures of 350 and 650 MPa for 0 (control), 3, 5, and 10 min at temperatures of 4.4 and 60.0 °C with and without 0.2% carvacrol. Treatments were conducted in PULSE tubes inside the chamber of the Hub880 Barocycler unit. In addition to microbial counts and for better assimilation of synergism of selected extrinsic factors of the study, linear (D-value) and non-linear (k) inactivation indices were calculated. A combination of mild heat, a low concentration of carvacrol, and mild pressure resulted in >5.0 log CFU/mL reduction ( < 0.05) in serovars, surpassing the log reductions obtained by the current high-pressure processing industry standard. Tennessee and the selected strain mixture exhibited comparable ( ≥ 0.05) sensitivity to pressure-based treatments, with D-values (350 MPa/4.4 °C) of 9.43 and 8.22 min, respectively. These values were reduced ( < 0.05) to 4.37 and 4.15 min, respectively, with the addition of 0.2% carvacrol to the pressure-based treatment. The application of mild heat at 60.0 °C and a low concentration of carvacrol showed microbiologically important synergism for augmenting the decontamination efficacy of high-pressure processing against nontyphoidal serovars.