Purpose: The objective of this study was to evaluate the efficacy of HPP for the destruction of E. coli in dry salami.
Methods: E. coli O121:H19 was grown in compatible solute-promoting media (Tryptic Soy Broth [TSB], and M9 medium containing glycine-betaine [M9-GB] or trehalose [M9-T]). Cells were harvested during stationary phase, inoculated onto sliced salami and vacuum packaged, stored for 9 d at 4°C, and then high pressure processed (600 MPa) after additional 0, 15, or 30 d refrigerated storage.
Results: E. coli O121 populations of 6.0, 5.24 and 4.81 log CFU/cm2 were obtained subsequent to inoculation on salami slices for cells grown in TSB, M9-GB and M9-T, respectively. Refrigerated storage of inoculated salami for 15 and 30 days resulted in E. coli O121:H19 reductions of 1.47 and 1.89; 0.92 and 1.31; and 0.42 and 1.03 log CFU/cm2, in salami inoculated with cultures grown in TSB, M9-GB and M9-T, respectively. E. coli reductions of 4.44, 3.15 and 3.18 log CFU/cm2 were obtained by HPP (3 min) of vacuum-packaged salami slices inoculated with cells grown in TSB and stored for 0, 15 and 30 days, respectively. Lower reductions were observed on salami inoculated with E. coli O121:H19 prepared in M9 media (M9-GB and M9-T) and stored for 15 or 30 days.
Significance: Inoculum preparation methods and acclimatization of the cells is critical during conduct of validation studies for HPP. High pressure processing can be used to achieve STEC reductions in dry salami and other fermented sausages as an alternative to a traditional post-fermentation heating step.