Suitability of Escherichia coli ATCC 11229 as Salmonella enterica surrogate for strawberry nectar pasteurization

Heat resistance, D- and z-values of five Salmonella enterica strains, namely S. Senftenberg LTH 5703, S. Typhimurium ATCC 13311 and ATCC 14028, S. Saintpaul LTH 6494, and S. Enteritidis ATCC 13076, as well as of a Salmonella cocktail and three potential surrogate strains were investigated in phosphate buffered saline and strawberry nectar (12° Brix). Thermal inactivation was performed at 60°C, 65°C, and 72°C. Moreover, the influence of pre-incubation under stressful environmental conditions on the heat resistance was tested. The results identified Escherichia coli ATCC 11229 as a suitable surrogate candidate for Salmonella strains, as its calculated D-values in both matrices were higher or statistically the same than those of the examined pathogens. The safety analysis showed no virulence factors that could classify E. coli ATCC 11229 as a pathogen. Furthermore, the results show significant differences in D-values of all strains in different matrices, which indicates a clear influence of the environment on heat resistance of bacteria. The pre-incubation under stress conditions had no significant effect on the heat resistance of E. coli ATCC 11229. However, further research is needed to explore the influence of stress conditions and duration on bacterial heat resistance.