THERMAL INACTIVATION OF YERSINIA ENTEROCOLITICA IN LIQUID EGG PRODUCTS*

Abstract

ABSTRACT Decimal reduction times (D values) and zD values for a three‐strain cocktail of Yersinia enterocolitica O:9 in three heat‐treated liquid egg products (whole eggs, egg yolks and egg whites) were determined. Products were inoculated at a final concentration of 2 × 107 cfu/mL and heated in capillary tubes to temperatures ranging from 51C to 64C for various time intervals. D values ranged from 0.06 (64C) to 11.30 min (55C) for liquid yolk, 0.058 (64C) to 11.29 min (55C) for liquid whole eggs and 0.39 (57C) to 9.88 min (51C) for liquid white. Thermal inactivation curves yielded zD values of 4.20C (whole eggs), 4.51C (egg whites) and 4.53C (egg yolks). D‐processes corresponding to the Y. enterocolitica inactivation during 3.5 min at temperatures required for egg pasteurization were estimated in 7D and 6.8D at 61C in liquid whole eggs and egg yolks respectively, and 8.9D at 57C in egg whites. The Y. enterocolitica risk should be considered in egg safety regulations.PRACTICAL APPLICATIONSEven though the prevalence of potentially pathogenic Y. enterocolitica on eggshell has been estimated to be 2.3% in our region, there is possible risk of penetration and proliferation of this microorganism into eggs during storage. In the present study, thermal inactivation techniques usually applied to eliminate Salmonella from liquid eggs were assayed on Y. enterocolitica‐contaminated liquid egg products. D and zD values calculated for this microorganism allowed to estimate the bactericidal effect produced by heating on these products. Knowledge related to the thermal inactivation of Y. enterocolitica from liquid egg products might contribute to food safety.