Synergistic Effects of Butyl Para-Hydroxybenzoate and Mild Heating on Foodborne Pathogenic Bacteria.

While high temperature heat treatments can efficiently reduce pathogen levels, they also affect the quality and nutritional profile of foods, as well as increase the cost of processing. The food additive butyl para-hydroxybenzoate (BPB) was investigated for its potential to synergistically enhance the thermal inactivation at mild heating temperatures (54 - 58 oC). Four foodborne pathogenic bacteria, Cronobacter sakazakii , Salmonella enterica serotype Typhimurium, attenuated Escherichia coli O157:H7 and Listeria monocytogenes, were cultured to early stationary phase and then subjected to mild heating in a model food matrix (Brain Heart Infusion) containing low levels BPB (≤ 125 ppm). The heating temperature used with each bacterium was selected based on the temperature that would yield an approximate 1 - 2 log reduction over 15 min heating in BHI without BPB using a submerged coil apparatus. The inclusion of BPB at concentrations ≤ 125 ppm resulted in significant enhancement of thermal inactivation, achieving 5 - > 6 log reductions of the Gram-negative strains and D-values of < 100 sec. Listeria monocytogenes achieved at 3 - 4 log reduction with a similar treatment. No significant inactivation was noted in the absence of the mild heating for the same time period. This study provides an additional proof of concept that low temperature inactivation of foodborne pathogens can be realized by synergistic enhancement of thermal inactivation by food components that affect microbial cell membranes.