Raw egg yolks have been treasured by cooks for centuries because of the way they thicken sauces. Over the last several years, though, it has become clear that for some people, they are no longer safe because of the risk of salmonella.
You can't live with 'em; you can't make mayonnaise without 'em. Or can you?
With the holiday season coming (and all of the attendant cooking and entertaining that accompanies it), we decided to try to find an alternative, a way of making egg sauces that are safer but still taste the way they should.
The first step was to know the enemy. Salmonella is a bacterium that thrives in poultry. So endemic has it become that it has even been found in the yolks of unbroken eggs, meaning that it is passed from hen to egg.
Salmonella can cause cramps, fever and diarrhea. Salmonella is especially dangerous for the very young, the very old and those with impaired immune systems. For the people in these groups, it can be deadly.
But salmonella can be killed by heat. The American Egg Board says that salmonella organisms will not survive if held at a temperature of 140 degrees or if they reach an endpoint of 160 degrees. "Cookwise" author and food scientist Shirley Corriher recommends heating eggs to 160 degrees for 1 minute. Food scientist and "The Curious Cook" author Harold McGee tells readers that in even the most heavily contaminated eggs, salmonella will be killed if eggs are heated to an endpoint of 182 degrees or if the temperature stays at 160 degrees for at least 3 1/2 minutes.
What makes egg yolks so special in sauce-making is their emulsifying characteristic: They allow oil and water to be beaten into a single uniform substance. That is why oil added to a raw egg yolk forms mayonnaise and why hot butter makes hollandaise.
The good news is that egg yolks will continue to emulsify even after some cooking, as long as the proteins in the yolk have not coagulated. The bad news is that between the safe temperature and the coagulation temperature, there's not much margin of error. Egg yolks begin to coagulate at 160 degrees.
But there's a trick that can make things easier. The presence of acid raises the temperature at which the egg yolk proteins coagulate. Add a little lemon juice or vinegar and the coagulation won't begin until the yolk reaches 170 degrees.
All of a sudden, you've got room to operate.
This is not an original discovery. Others have made sauces based on this information, including food scientists McGee and Corriher,the American Egg Board and cookbook legend Julia Child.
What we did was investigate each of their methods and then synthesize them to come up with our own versions.
In trying different mayonnaise recipes, for example, we found that the textures varied widely, depending on the method used to heat the yolks and on the amount of liquid present.
McGee's method calls for heating yolks with water and lemon juice in a microwave oven until the mixture is near-boiling, visually, when it begins to "heave and bubble." Oil is then whisked in along with the rest of the flavorings. This has an acceptable texture, but it tastes slightly "cooked," almost like a hollandaise.
Corriher and the Egg Board use similar sterilization techniques, heating the egg yolks with liquid and acid directly on a stovetop to a lemon curd-like consistency, then beating in the oil. The difference is that Corriher's recipe calls for more liquid, resulting in a lighter, smoother result. In fact, it was quite close to our "control" batch of homemade mayonnaise.
Hollandaise is not so easy. We made six batches and found that none of them met our taste test. Some were too thick, some were too thin, one was actually sweet and another tasted more like white sauce than hollandaise.
In the end, we wound up taking bits from several of the methods. We cooked whole eggs, chicken stock and lemon juice together, then whisked in cubes of butter. It tastes very close to normal hollandaise, but with no danger of salmonella.
See, you can have your egg sauce and eat it too.
This recipe uses chemist and food writer Shirley Corriher's method. Use a mild-flavored oil such as vegetable or canola; unrefined or extra-virgin olive oil produces a less stable emulsion. If you don't have an electric mixer, a blender or food processor will do. Of course, hand whisking is more than acceptable.
2 egg yolks
1 tablespoon Dijon-style mustard
1 teaspoon white wine vinegar
1 tablespoon water
1 cup oil
Combine yolks, mustard, vinegar and water in small saucepan. Stir and scrape mixture over very low heat 3 to 4 minutes until mixture is thickened like lemon curd and reaches temperature of 160 degrees for at least 1 minute. Remove from heat and transfer to mixing bowl.