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The Great Raw-egg Dilemma

Since the untimely end of Edwina Currie?s brief ministerial career, most people know that some eggs are contaminated with Salmonella, a nasty little bug that causes food poisoning serious enough to kill vulnerable babies and old people. Those of us blessed with galvanised-iron guts just get sweaty, shaky, headachy and sick, but the experience is still to be avoided.

Patricia and I recently passed our basic food hygiene course with credit, #so we know more about this issue than we did when I first wrote this item. The basic recommendation is that when you cook or re-heat anything, the core temperature should reach at least 75ºC. The exception is the interior of solid meat (not mince, burgers or rolled joints), which can be assumed to be OK - so rare roast beef is fine provided all surfaces that have at any time been exposed to the air are thoroughly seared.

75ºC gives a reasonable margin of safety, since one form of pasteurisation requires food to be held at 71ºC for only 15 seconds, while another needs only 62ºC but for half an hour. 62ºC is the lowest safe temperature for keeping foods warm - some bacteria can be active if the temperature is any lower.

While we?re on the subject, 8ºC is the highest safe temperature for keeping anything chilled, but fridges ought to be held at between 1ºC and 5ºC.

But back to eggs. We were told that the only safe assumption with chickens and their eggs is that they are crawling with Salmonella. So home-made mayonnaise and its derivatives are risky. Having said that, I?ve made mayonnaise plenty of times and I?ve never been aware of any problems. I wouldn?t give it to my 89-year-old mother, though.

But what about cooked egg emulsions like lemon curd, hollandaise and bearnaise sauces and custards?

When I make lemon curd, it thickens some minutes after its temperature has reached 75ºC on my Dad?s trusty lab thermometer, so that?s fine.

Hollandaise is more problematical, since vigorous whisking can make it thicken at quite low temperatures. Harold McGee in On Food and Cooking - The Science and Lore of the Kitchen (a wonderful book if, like me, you?re curious about why you do things, as well as how). suggests that a successful egg-butter sauce should not be heated to more than 66ºC, which makes the process pretty marginal in bacteriological terms. However, I recently made both hollandaise and bearnaise for a cold buffet, and found that I was able to heat the yolks and the reduction to 75ºC before starting to add the butter, which I had also melted and kept at 75ºC. To my amazement, the sauces were thicker and more stable than any I?d ever made before.

Since I learned all this, and since we started the catering business, I?ve come to depend more and more on a thermometer. I have a brilliant electronic one now with a probe you can shove into a roasting joint and an armoured cable you can slam the oven door on. It even has an alarm that sounds when the meat reaches the target temperature.

Personal site for Paul Marsden: frustrated writer; experimental cook and all-round foodie; amateur wine-importer; former copywriter and press-officer; former teacher, teacher-trainer, educational software developer and documenter; still a professional web-developer but mostly retired.

This site was transferred in June 2005 to the Sites4Doctors Site Management System, and has been developed and maintained there ever since.