Friday, August 20, 2010

Would you like your Salmonella over easy or sunny side up, sir?

550,000,000 eggs have now been withdrawn from the market in two recalls in USA.

380m eggs were recalled early last week by Wright County Egg and now 170m eggs have been recalled by Hillandale Farms of Iowa.  Eggs from both companies have been linked with salmonellosis affecting at least 1700 people.

Salmonella is a bacterium found in the gut of man, animals and birds.  It causes nausea, vomiting, abdominal pain and diarrhoea that may last for several days and can be fatal in the very young or elderly.  It is usually contracted by ingestion of faecally contaminated food, though this is not the only route of infection.  The disease is described as a “food borne infection”, because after ingestion of infected food, the bacteria grow in the gut, causing the symptoms, which appear 12 to 14 hours after ingestion. 

Why have so many eggs been withdrawn?  I think it’s probably because of the way the regulations governing poultry farming in the US are written.  As I understand it, testing is conducted under the FDA “Egg Rule” -Environmental Testing for Salmonella Enteritidis (21 CFR 118.5).  Samples are taken from the environment to determine if S. Enteritidis is present, because this is an indicator of the effectiveness of the SE control plan.  The pullet environment is tested when the pullets are 14 – 16 weeks old and in addition, the environment in each poultry house is tested when any group of laying hens reaches 40 – 45 weeks of age.  

If rodents, birds or insects introduce Salmonella to the poultry house, between testing times, the infection could spread rapidly throughout the flock and eggs could be produced from infected hens. Hens can become infected internally and eggs can be infected before the shell is formed.  There is no way to tell if an egg is infected with Salmonella, other than cracking it and culturing the contents. Eggs are required to be tested only when an environmental sample is shown to be positive.  So the huge recall is to ensure that all potentially contaminated eggs are removed from the market place and homes.

How can consumers protect themselves from contracting salmonellosis?  The most obvious precautions are the proper refrigerated storage and cooking of eggs, washing hands after handling eggs and avoidance of products containing raw eggs, such as home made ice cream and mayonnaise, or coddled eggs.  If you have eggs subject to the recall, dispose of them or return them to the retailer for a refund.

Eggs in New Zealand are unlikely to contain Salmonella.  In the next posting, I’ll discuss this and the latest on Campylobacter in New Zealand.

Just a thought:  How are they going to dispose of 550m eggs?  At 60g (about 2 ounces) each, that is about 33,000 tonnes (36,376 US tons) of eggs.


Helen Baron-St John said...

My local supermarket sells eggs from a non-refrigerated shelf. Is this safe, or should they be refrigerated at point of sale?

John said...

This is not quite so easy for me to answer. There may be local, or country-specific regulations.

However, the Egg Producers Federation of New Zealand Code of Practice (which is a guideline, rather than a regulation) states that Clean Shell Eggs for retail, wholesale, supply to secondary processors or food service shall be held at or below 15C.

The intent of refrigeration or cool storage is to reduce the potential growth rate of Salmonella and other bacteria that might be contained in or enter the eggs.

The New Zealand Food Safety Authority document "Animal Products (Specifications for Products Intended for Human Consumption) Notice 2004" requires eggs be handled and stored under conditions that minimize condensation on the surface of the eggs. Effectively, that means that temperature changes should be avoided and cold eggs should not be brought into warm humid conditions. This is because the shells are not impermeable and bacteria can pass through the shell in moisture.

Incidentally, Food Standards Australia/New Zealand forbids the sale of cracked eggs for retail or catering purposes.

Tanvi Shinde said...

Purude university professor have reported that cooling the eggs at around 45 degrees F soon after they are laid can hinder the ability of Salmonella to grow in eggs. He has come up with rapid cooling technology and the Purdue-based Indiana State Poultry Association is keen on adopting this technology to eliminate future outbreaks. Interesting innovation check it out -

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