Using cold water instead of warm during a second wash of eggs can help cooling, which reduces the risk of pathogen growth both inside and outside the shell, according to research published yesterday.
The test findings may provide egg producers and processors with a simple, low-cost means of reducing pathogen contamination even further.
Contamination is a continuing problem for egg producers, due to the high prevalence of pathogens, such as Salmonella, in egg-laying hens. Washing the shells before processing is known to reduce the incidence of pathogens caused mainly by fecal matter on eggs.
Researchers with the US Department of Agriculture (USDA) together with those from Auburn University, studied the frequency of Salmonella, Campylobacter, Listeria and other pathogens in eggs commercially washed in cool water. Their findings were reported in the Journal of Food Safety.
Egg processors need to use wash water of at least 90F, or 20F warmer than the warmest egg entering the processing line to meet USDA quality standards.
Furthermore, the eggs must be sprayed with a sanitising rinse that is at least the same temperature as the washing water.
The eggs must then be quickly cooled to prevent pathogen growth associated with warmer temperatures.
USDA requirements state that eggs for human consumption must then be stored at 45F or below as quickly as possible.
The researchers tested three water temperature schemes in dual washing commercial systems. The first test used water at 120F for both washes of the eggs.
The second used water at 120F for the first wash and 75F for the second. The third used water at 75F for both washes.
They found that using warm temperature water in a first wash and cooler water in a second wash could provide the greatest benefit by both reducing egg temperature and microbial levels.
While Salmonella, Campylobacter and Listeria were all detected in shell emulsion and wash-water samples from cool-water washing treatments, none were detected in the eggs contents throughout the storage period of eight weeks.
Salmonella and Campylobacter pose major problems to processors who use eggs.
In June the European Food Safety Agency (EFSA) published a study, which found about one in five of the EU's large scale commercial egg producers have laying hens infected with the Salmonella spp. pathogen.
The study found Luxembourg and Sweden had the lowest levels of infection. The highest rates, ranging from 52 per cent to 80 per cent of holdings, were found in Portugal, Poland and the Czech Republic.
The EU's current Zoonoses Regulation, sets out plans that would from 2010 ban completely the retail sale of eggs from Salmonella-infected flocks. Eggs will have to undergo a sterilisation procedure if they are to be used for processing into egg products.
The European Commission is considering the feasibility of accelerating the ban on marketing eggs from Salmonella-infected flocks.
A Commission study published last year found there were 192,703 reported cases of salmonellosis and 183,961 of campylobacteriosis cases reported during 2004 in the EU's 25 member states.
The cases are out of a total of 400, 000 human cases of zoonoses reported. Most of the cases were foodborne and associated with mild to severe intestinal problems.