To improve the efficacy and safety of egg washing

Project Title: To improve the efficacy and safety of egg washing

Project Leader: Sexton at SARDI funded by Poultry CRC – Sub-Project 3.2.1

Duration of Project:
1 October 2010 to 30 June 2012

Project overview

The annual production of eggs in Australia totalled 333.9 million in 2008/09, of which 67.8% were cage eggs, 5.5% were barn laid and 26.8% were free range (Australian Egg Corporation Limited, 2009 Annual Report). The vast majority of eggs are washed prior to packing to remove dirt and faecal material to reduce the microbial contamination of the egg shell. Eggs which are not visually clean after washing are frequently diverted for pasteurisation, along with cracked eggs, resulting in lower returns to the processor.

The washing process consists of several stages – pre-washing, washing with the aid of a surfactant / detergent, sanitising and blow-drying – and can take less than 30 seconds. Hence, the effectiveness of the surfactant’s ability to penetrate and effectively remove dirt and faecal matter is critical for the recovery of table eggs. An effective detergent can also assist in the removal of bacteria while a suitable sanitiser, together with a clean post-wash processing environment, will assist in maintaining the hygienic status of the eggs.

Production of visually clean eggs, free from dirt and faecal contamination, is the primary concern in the supply of table eggs. However, clean eggs do not guarantee food safety. Salmonella spp. is the main pathogen of interest internationally. In Europe and the USA, Salmonella Enteritidis PT4 is of greatest concern because of its trans-ovarian transmission route into the egg. Even so, the majority of the published literature is on the effectiveness of different egg washing and processing methods to reduce or eliminate Salmonella Enteritidis from eggs.

Salmonella Enteritidis PT4 has not been detected in the Australia egg industry, however, other Salmonella strains are still of interest. Previous work undertaken for the Australian Egg Corporation Limited (Daughtry et al 2005) indicated that Salmonella contamination of unwashed eggs in Australia was very low. Daughtry et al (2005) found that these figures compare favourably to other countries with similar production systems.

While the prevalence of Salmonella contamination of egg shells is low in Australia, additional reductions in Salmonella contamination due to effective egg washing would further reduce the risk to consumers. Effective egg washing is also expected to improve the general microbiological status of eggs, as determined by Total Viable Counts (general hygiene indicator) and E. coli and Enterobacteriaceae (indicators of faecal contamination).

This project is in line with the Australian government’s R&D priorities for the egg industry – Boosting industry productivity and adding value (Australian Egg Corporation Limited, 2009 Annual Report). The primary beneficiaries of this research project will be members of the egg processing sector through improved recovery rates of table eggs. In addition, improvements in processing hygiene, post washing, may help maintain or improve the shelf-life and food safety of eggs. Consequently, consumers of table eggs will benefit as will the food service sector.

Project objectives

The primary objective of this project is to improve the effectiveness of current washing practices to reduce the proportion of eggs downgraded or disposed, resulting in increased economic returns to industry. The secondary objective is to further improve the quality and safety of eggs to reduce food safety risks and business risk for egg producers arising from suspected food borne outbreaks where eggs are suspected.

To identify and trial effective egg washing chemicals to improve the visual appearance of eggs, laboratory based trials will be undertaken to assess three surfactant and sanitiser combinations. These trials will be performed on eggs which are naturally and artificially contaminated with dirt and faeces. The most effective chemicals will then be assessed in several trials undertaken in commercial settings. The outcome will be improved recovery of table eggs which will provide economic benefits to egg processors.

To assess the effectiveness of surfactant and sanitiser combinations for improving the hygiene and safety of eggs, laboratory trials to assess the effectiveness of reducing visual contamination will also be utilised to assess the effectiveness in reducing hygiene and faecal indicators on the surface of egg shells. Eggs will also be artificially inoculated with Salmonella and the reduction in levels after washing and sanitising will be measured.

Project progress

By December 2010, an appropriate method for preparation of a faecal slurry and inoculation of eggs had been identified that results in eggs that are visually similar to naturally dirty eggs. This method will be used for the remainder of the project when dirty eggs are required.

See also

• Egg
• Salmonella
• Food safety principles
• Chicken layer industry
• SARDI
• Poultry CRC
• Australian Egg Corporation Limited