Inactivation of Salmonella Enteritidis and Salmonella Senftenberg in liquid whole egg using generally recognized as safe additives, ionizing radiation, and heat

Abstract

The effect of combining irradiation and heat (i.e., irradiation followed by heat [IR-H]) on Salmonella Enteritidis and Salmonella Senftenberg inoculated into liquid whole egg (LWE) with added nisin, EDTA, sorbic acid, carvacrol, or combinations of these GRAS (generally recognized as safe) additives was investigated. Synergistic reductions of Salmonella populations were observed when LWE samples containing GRAS additives were treated by gamma radiation (0.3 and 1.0 kGy), heat (57 and 60°C), or IR-H. The presence of additives reduced the initial radiation Dγ-values (radiation doses required to eliminate 90% of the viable cells) by 1.2- to 1.5-fold, the thermal decimal reduction times (Dt-values) by up to 3.5- and 1.8-fold at 57 and 60°C, respectively, and the thermal Dt-values after irradiation treatments by up to 3.4- and 1.5-fold at 57 and 60°C, respectively, for both Salmonella serovars. Of all the additives investigated, nisin at a concentration of 100 IU/ml was the most effective at reducing the heat treatment times needed to obtain a 5-log reduction of Salmonella. Thus, while treatments of 21.6 min at 57°C or of 5 min at 60°C should be applied to achieve a 5-log reduction for Salmonella in LWE, only 5.5 min at 57°C or 2.3 min at 60°C after a 0.3-kGy radiation pretreatment was required when nisin at a concentration of 100 IU/ml was used. The synergistic reduction of Salmonella viability by 1R-H treatments in the presence of GRAS additives 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) or to increase the level of Salmonella inactivation.