THE WORLD鈥橲 first pasteurised fresh eggs will go on sale in the US this
autumn, thanks to a machine called 鈥淏ig Pete鈥�. The machine kills the
Salmonella enteritidis bacteria which grow inside the egg without
solidifying either the yolk or the white.
But European customers may have to wait for their safe runny eggs, despite
the dangers of food poisoning
(This Week, 11 April, p 5). Some of the steps in
the pasteurisation process are banned in Europe and food safety laws will have
to be changed before the technique can be adopted. The process has been approved
by the US Department of Agriculture.
Pasteurized Eggs, the company in Laconia, New Hampshire, which developed Big
Pete, says that the raw eggs treated with the technology will be as safe as
pasteurised milk. 鈥淧asteurised milk is universally accepted as safe,鈥� says John
Davidson, the founder of Pasteurised Eggs and the brains behind Big Pete. 鈥淲e
want people to feel exactly the same about our eggs,鈥� he says.
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鈥淧eople will be able to go back to eating eggs with runny yolks, as well as
dishes made with raw eggs such as Caesar鈥檚 salad dressing and homemade
mayonnaise,鈥� says Davidson. 鈥淚t鈥檚 truly a major breakthrough.鈥� The process adds
2 cents to the cost of an egg, says Davidson.
Using technology originally developed by James Cox, an inventor and colleague
who died last year, Davidson had to find a way of applying enough heat to kill
bacteria without cooking the egg. The ideal compromise, he found, is to gently
heat-treat individual eggs in baths of water over periods of about an hour.
The eggs arrive on a conveyer belt and are successively dunked in baths of
sterilised water heated to between 62 掳C and 72 掳C. They have been weighed
to determine how long they should be treated for.
Davidson will not reveal the exact temperatures required, but says that the
first bath is the hottest. It allows the heat to penetrate slowly through the
egg white to the border of the yolk. 鈥淵ou have to achieve transfer of the heat
through the albumin egg-white protein without cooking it,鈥� he says.
Balancing the heat transfer in the yolk and the albumin is the key to the
process, says Davidson. 鈥淭he albumin is a thinner liquid, and is therefore more
sensitive to heat, both through its density and its chemical composition,鈥� he
says.
In the second, slightly cooler bath, the heat which has already reached the
yolk gently radiates inwards until it reaches the centre. In the final bath, the
job is completed by raising the temperature again. For unknown reasons , raising
the temperature again accelerates the pasteurisation, without damaging the
albumin. Ammonium salts sterilise the water baths, killing bacteria in faeces
and muck sticking to the eggshells.
Finally, the eggs are dunked for 20 minutes in cold water to bring them down
to refrigerator temperature. The process can treat 1000 eggs a minute.
But dunking Class A eggs, those fresh eggs that are sold directly to the
public, is illegal in Europe鈥攁 measure that is designed to prevent faecal
bacteria finding its way into the eggs. 鈥淵ou can鈥檛 wash Class A eggs and that鈥檚
it,鈥� says a spokeswoman for Britain鈥檚 Ministry of Agriculture Fisheries and
Food.