January 21, 2014


US researchers evaluate best practices for shell egg sanitisation



A recently completed research project by Texas A&M University, which investigated current and alternative practices of shell egg sanitisation based on efficacy, egg quality and economics, aim to provide guidance in formulating future best practices for the industry.


The research, entitled 'Development of best practices for shell egg disinfection based upon efficacy, egg quality and economics', is conducted by Dr Craig Coufal and Dr Christine Alvarado from Texas A&M University in College Station, Texas, the United States. The researchers surveyed egg processors across the US to determine current practices and costs of shell egg sanitisation.


In addition, they conducted a microbial survey to evaluate the effectiveness of current practices. Their research also involved evaluating the effectiveness of prewash egg disinfection procedures, determining the efficacy and quality parameters of current methods compared to alternative methods and conducting an economic analysis to compare current and alternate methods of shell egg sanitisation.


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 sanitisation processes listed above do not completely disinfect the surface of shell eggs during processing. As a result, more effective eggshell sanitisation technologies are needed to help assure the safety of shell eggs and egg products.


The survey of egg processors across the US indicated that egg sanitisation practices are quite standardised 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 sanitisation process prior to egg washing or conduct microbiological monitoring.


Eggs sampled from six egg packing plants in Texas verified that currently used egg sanitisation 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.


Several experiments were conducted to compare the effectiveness of eggshell disinfectants currently used in the egg industry to alternative methods of peracetic acid (PAA), PAA in combination with UV light, and H2O2 in combination with UV light. Peracetic acid was found to be more effective than chlorine but less effective than QAC. Hydrogen peroxide with UV light was the most effective sanitiser, resulting in zero microbial counts on most eggshells.


Sensory panel evaluation indicated that eggs treated with H2O2 and UV light were perceived by consumers to be equal to untreated eggs and eggs treated with QAC, but eggs treated with chlorine received the highest scores for taste and texture. While H2O2 with UV light was found to be a superior eggshell disinfectant compared to methods currently used in the egg industry, the cost is greater.


In addition, experiments conducted to evaluate the effectiveness of various disinfectants to reduce Salmonella inoculated on eggshells found that all the disinfectants, including those currently used in the egg industry, reduce Salmonella on eggshell surfaces to levels below detection by rinse and plate sampling technique.


The research project is funded by USPOULTRY and the USPOULTRY Foundation. The project is part of the association's comprehensive research programme encompassing all phases of poultry and egg production and processing.