I’m not sure why, but I hear this more often in summer: “Hope there’s no mayo in that salad/sandwich?” Yes, it could be just calorie counting, but a little probing often produces a variant of this reaction: “But it’s made with raw eggs. They carry salmonella.”
The strange thing is that these same people would gladly eat a fried egg, entirely free of anxiety—since it’s cooked. But the egg protein doesn’t coagulate in your perfect sunny side up since the temperature isn’t high enough to kill the salmonella bacteria.
So where is this pesky salmonella?
Eggs with salmonella, if not cooked properly, can cause infection, resulting in diarrhoea and fever, that can even prove fatal.
There are two different places you can find salmonella in an egg—deep inside and on the surface. If the hen is infected, the bacteria may well be deep inside the yolk. But not every egg from an infected layer has salmonella (some estimate it to be only 1 in a 1000). Or the bacteria could be on the shell, which is more common. This means, for instance, that droppings from an infected hen could contaminate the healthy neighbour’s eggs.
You might think the latter’s not a big problem. But you can’t make an omelette and break no eggs. And once that shell cracks, the bacteria could slip in.
Killing salmonella the home-made way
The surest way to kill the bacteria is to cook your eggs thoroughly at a temperature of at least 56 degrees Celsius.
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The chances of infection are higher when soft cooking methods are used—as in scrambling, frying or soft-centred omelettes—according to a 2008 US study published in the Poultry Science journal. So if you must dip into soft yolk safely, boil the whole egg till the whites are firm and the yolk still oozing. And while traditional pan poaching in water is reliable, eggs poached in a microwave can still retain salmonella as the cooking time is too brief, a 1995 UK study found.
By the way, unlike with some other pathogens, freezing won’t kill salmonella, so ice cream made with egg could also be contaminated.
Salmonella also cannot thrive in an acidic environment. So where you can’t heat, sour. Of course, several commercial recipes for mayonnaise are egg-free. But if you want the real stuff, you’re best off making your own, because not all recipes get the pH low enough for safety. Adding 20-35ml lemon juice per egg yolk in the recipe and keeping the mayonnaise at 22 degrees Celsius for at least 72 hours before consumption or refrigeration does the trick, according to a 1999 study at Leeds Metropolitan University, UK.
Safe or sumptuous?
This is by way of a confession: I’m not about to cease and desist, whether it comes to a sunny side up or a fresh-made Hollandaise. And mayo is not going off the menu either.
Do take some precautions, such as avoiding poultry farm eggs where hens are huddled together, cross-infecting speedily. I put a lid on the frying pan to hold the heat in. Is a delicious meal worth the Russian roulette? Knowing the numbers, I’d say a cautious yes…though I would draw the line at fugu.
The author is deputy features editor at Mint.