Title: Behavior of Avirulent Yersinia pestis in Liquid Whole Egg as Affected by Antimicrobials and Thermal Pasteurization Authors
Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2009
Publication Date: March 24, 2010
Citation: Gurtler, J., Rivera, R.B., Zhang, H.Q., Sommers, C.H. 2010. Behavior of Avirulent Yersinia pestis in Liquid Whole Egg as Affected by Antimicrobials and Thermal Pasteurization. Journal of Food Safety. 30:537-557. Interpretive Summary: The bacterium Yersinia is currently not a problem in pasteurized liquid egg products, although it has been isolated from eggs in the United States and Argentina. Yersiniae, which are psychrotrophic bacteria, and can grow at temperatures as low as minus 2 degrees Celsius; therefore, incidental or intentional contamination of liquid whole egg (LWE) with this pathogen could result in multiplication to high populations, even when stored under refrigeration (approximately 4 degrees celsius). The current study has demonstrated that a non-infectious Y. pestis is able to multiply in LWE at 4 degrees Celsius. We have also found that current USDA liquid egg pasteurization standards are more than sufficient to eliminate this bacterium from contaminated LWE. Ten antimicrobial additives were also evaluated to determine their usefulness in controlling Yersinia in liquid whole egg when stored at various temperatures over time. This study provides information that will be helpful in determining thermal and nonthermal means of controlling yersiniae in liquid egg products.
Technical Abstract: Yersinia spp. is a psychrotrophic bacterium that can grow at temperatures as low as minus two degrees Celsius, and is known to contaminate shell eggs in the United States and shell eggs and liquid egg in South America. A study was performed to determine the thermal sensitivity of avirulent Yersinia pestis in liquid whole egg (LWE), evaluate the growth pattern of the pathogen at temperatures of 4 to 22 degrees Celsius, and assess the ability of ten antimicrobial compounds to inhibit the growth of non-pathogenic Y. pestis in LWE over time. The decimal reduction values of attenuated Y. pestis in LWE at 54 degrees Celsius (D54) were found to be 1.40 to 1.58 min and D60 values were 13.6 and 11.13 seconds by the addition of 0 and 965 IU of nisin, respectively. Low molecular weight chitosan (0.5 percent) and an activated lactoperoxidase system (2.18 U per ml) in LWE were ineffective at inhibiting growth of the pathogen, while 500 IU per ml nisin inhibited populations by up to 1 log CFU per ml in LWE at 4, 10 and 15 degrees celsius, when compared to the control. Seven other antimicrobials inhibited growth when added at high levels. Further testing is needed to determine additive or synergistic effects of these antimicrobials when used in combination and sensory thresholds of these compounds in LWE.