Purpose: The aim of the present study was to evaluate the effect of lactate and diacetate on the HP inactivation of L. monocytogenes in cooked ham.
Methods: Cooked ham batches were manufactured with: 1.4% potassium lactate (L14), 2.8% potassium lactate (L28), 0.1% sodium diacetate (D) and 1.4% lactate plus 0.1% diacetate (LD). Once sliced, products were inoculated with L. monocytogenes (three different strains, i.e. CTC1011, CTC1034 and ScottA, independently). Vacuum-packed samples were pressurized at 400 MPa for 9 different holding times (0-10min). L. monocytogenes survival was monitored by enumeration on chromogenic medium. Inactivation kinetics was evaluated by fitting primary models to the survival data obtained by each product formulation and strain.
Results: The HP inactivation kinetics observed for L.monocytogenes depended on both the product formulation as well as the strain. Overall, the presence of lactate caused a piezo-protection as the inactivation rate was lower in cooked ham formulated with lactate than in the control product. The higher the lactate concentration, the lower the inactivation rate. By contrast, diacetate slightly enhanced HP inactivation of L. monocytogenes. A notable difference was denoted in the primary kinetic behavior among the studied strains. A shoulder shape was observed for the product isolates (CTC1011 and CTC1034), while a tail was recorded for the clinical isolate (ScottA).
Significance: The design, validation and implementation of high pressure processing requires a tailor-made approach, taking into account the specific product formulation and also selecting the most appropriate strains for process validation.