Behavior of enterococci in egg processing operations.

Abstract

Since enterococci were detected in dried and frozen egg products (whole egg and egg yolk), the origin of the enterococci and their behavior in the different stages of egg processing were surveyed. The bacterial survey of unwashed and washed eggs, gathered from several parts of Japan, showed the presence of an average of 60 enterococci per egg on the shell surface of unwashed eggs. Smaller numbers of enterococci were detected on the shell surface of washed eggs. Most of the detected enterococci were Streptococcus faecalis and S. faecalis var. liquefaciens. The contents of two eggs were contaminated with enterococci when 120 washed eggs were examined. Enterococci were destroyed to some extent by the disinfectants used for washing the shell eggs, but they seemed to have greater resistance than Escherichia coli and Pseudomonas fluorescens used for comparison. In whole egg and egg yolk, enterococci grew rapidly at 25 C, slowly at 10 C, and very slowly at 2.5 C. The frozen storage of both whole egg and egg yolk at -20 C for 3 months only slightly decreased the number of enterococci. They were decreased only slightly by normal pasteurization but were destroyed in the desugaring process by the glucose oxidase method. Enterococci numbers were only slightly decreased by spray-drying whole egg and yolk. Considering these characteristics of enterococci, it appears to be difficult to produce enterococci-free egg products in a normal production line.