Keeping egg yolks at 180 degrees for one minute eliminates any salmonella risk without cooking them hard, reports food-science writer Harold McGee in his book "The Curious Cook." Even yolks infected with billions of salmonella bacteria have come through this process totally sterilized but still usable--with a certain amount of care--for making sauces such as hollandaise and mayonnaise.
The McGee technique is to mix yolks with lemon juice and water and cook to a near boil in a microwave oven, removing and beating partway through to ensure that no lumps of hard-cooked yolk develop. The acidity of the lemon juice hinders curdling; the water also helps maintain consistency. Then the mixture sits covered to ensure that the yolks stay at 180 degrees for one minute.
Some important tips: Never add salt before cooking yolks because it makes them curdle. And be sure to have several clean forks or whisks on hand for making sterilized yolks. Using a dirty fork or whisk from a previous stage of sterilization could reinfect the yolks.
The cooked yolks have a custard-like consistency but can be treated for sauce-making purposes like raw yolks . . . almost. "Not surprisingly," McGee writes, "since near-boiled yolks have taken a beating before they ever see butter, sauces made by this method are more fragile than the standard versions." When making hollandaise, he advises, don't let the temperature get above 120 degrees.
If you want mayonnaise with the traditional Mediterranean flavor, you should include some olive oil in the recipe. But when using sterilized egg yolks, McGee says, be sure that olive oil is no more than 1/4 of the total of the oil you use. Mayonnaise made with near-boiled yolks will lose its consistency overnight if there's a higher proportion of olive oil.
Sterilized Egg Yolks
3/4 cup unsalted butter
Place Sterilized Egg Yolks in small saucepan. Whisk in dash salt. Turn heat on low, add butter and beat slowly just until melted into sauce. Strain and correct seasoning with salt and lemon juice. Makes scant 1 cup.
Sterilized Egg Yolks
2 large egg yolks
2 teaspoons lemon juice
2 tablespoons water
Beat egg yolks until smooth in 2-cup glass measure or other small glass bowl with fork or wire whisk. Add lemon juice and beat again. Add water and beat again. Throw now-dirty fork or whisk in sink, or wash in hot soapy water.
Cover bowl with plastic wrap, place in microwave and cook on HIGH (100% power) until yolks begin to move. (Watch through oven window, standing back several feet, or open oven door at 10-second intervals after 30 seconds to check.) When yolks begin to move, cook 8 to 10 seconds longer and remove. Beat yolks until smooth with clean fork or whisk. Throw now-dirty fork or whisk in sink.
Return yolks to microwave and heat on HIGH until yolks begin to heave again. Remove and beat vigorously with clean fork or whisk until smooth. Cover and let stand 1 minute.
Note: If using extra-large egg yolks, use 2 tablespoons plus 2 teaspoons water.
Sterilized Egg Yolks, cooled
1 to 2 cups oil
Place Sterilized Egg Yolks in food processor and process until smooth. Slowly add oil in thin, steady stream. Add salt and 1 to 1 1/2 tablespoons lemon juice to taste. Process until mixture is thick and smooth. Makes about 1 1/4 to 2 1/4 cups.