Development Of Best Practices For Shell Egg Disinfection Based Upon Efficacy, Egg Quality And Economics

By Dr. Craig D. Coufal, Dr. Christine Z. Alvarado

Salmonella contamination of shell eggs and subsequent recalls in 2010 resulted in economic losses to the egg industry and increased consumer concerns about the safety of eggs. In addition, HACCP regulations for egg processing are probable in the near future. Treatment of eggs with chlorine or quaternary ammonium (QAC) sprays as a final disinfection step following washing has been the standard for egg processing in the US for decades. The use of ultraviolet light (UV) as a final disinfection step for shell egg processing has been approved by the USDA but has not gained widespread use in the US egg industry. Previous research has indicated that all the egg sanitization processes listed above do not completely disinfect the surface of shell eggs during processing. As a result, more effective eggshell sanitization technologies are needed to help assure the safety of shell eggs and egg products.

The overall goal of this project was to develop and evaluate improved egg sanitization processes for shell eggs to enhance food safety.

The specific objectives were to:

1) survey egg processors across the US to determine current practices and costs of shell egg sanitization;

2) conduct a microbial survey of egg processing facilities to evaluate current sanitization of shell eggs;

3) evaluate the effectiveness of prewash egg disinfection procedures;

4) determine efficacy and quality parameters of current methods of egg sanitization compared to alternative technologies; and

5) conduct an economic analysis to compare current and alternative methods for the sanitization of shell eggs.

The survey of egg processors across the US indicated that egg sanitization practices are quite standardized across the industry. This is not surprising since 77% of respondents indicated they were processing eggs under inspection (presumably USDA) and must, therefore, follow set guidelines.  Eighty-three percent of egg processors are using a chlorine solution rinse in the final disinfection step. Results also indicate that few processors apply a sanitization process prior to egg washing or conduct microbiological monitoring. Eggs sampled from six egg packing plants in Texas verified that currently used egg sanitization methods significantly reduce the microbial load on eggshells but usually leave a low level of bacteria remaining on the eggshell surface (2.1 log10 cfu/egg).

Four trials were conducted to evaluate the use of hydrogen peroxide (H2O2) in combination with UV light to treat eggs prior to washing. Results indicated that treatment prior to washing resulted in fewer dirty eggs following washing, and visibly clean eggs after washing had lower microbial counts if they were treated prior to washing.