Design of a combined process for the inactivation of Salmonella Enteritidis in liquid whole egg at 55 °C

This paper is an evaluation of the lethal effectiveness of a successive application of pulsed electric fields (PEFs) and heat treatment in liquid whole egg (LWE) in the presence of different additives on the population of Salmonella serovar Enteritidis. Synergistic reductions of the Salmonella Enteritidis population were observed when LWE samples containing additives were treated with PEF (25 kV/cm; 100 and 200 kJ/kg), heat (55 °C), or PEF followed by heat. The presence of additives, such as 10 mM EDTA or 2% triethyl citrate, increased the PEF lethality 1 log10 cycle and generated around 1.5 log10 cycles of cell damage, resulting in the reduction of undamaged cells of 4.4 and 3.1 log10 cycles, respectively. The application of PEF followed by heat treatment significantly (p < 0.05) reduced D55ºC from 3.9 ± 0.2 min in LWE to 1.40 ± 0.06 min or 0.24 ± 0.02 min in the presence of 10 mM EDTA or 2% triethyl citrate, respectively. A PEF treatment of 25 kV/cm and 200 kJ/kg followed by a heat treatment of 55 °C and 2 min reduced more than 8 log10 cycles of the population of Salmonella Enteritidis in LWE combined with 2% triethyl citrate, with a minimal impact on its protein soluble content. The heat sensitizing effect of PEF treatments in the presence of 2% triethyl citrate on the Salmonella population could enable LWE producers to reduce the temperature or processing time of thermal treatments (current standards are 60 °C for 3.5 min in the United States), increasing the level of Salmonella inactivation and retaining the quality of non-treated LWE.

Research highlights
► 8-log-reductions of S. enteritidis in liquid whole egg at 55 °C.
► PEF-heat-triethyl citrate is an alternative to heat pasteurization of LWE.
► PEF lethality and cell damage of S. enteritidis increase by adding additives to LWE.
► S. enteritidis heat resistance in LWE is reduced by applying a previous PEF treatment.
► Triethyl citrate reduces 16 fold S. enteritidis heat resistance after a PEF treatment.