A good rule of thumb for cooking with dairy products, including cream, milk, eggs, butter, cheese and mayonnaise, is: patience!
Sauces made with milk, cream and cheese may curdle for several reasons:
- not enough fat content. Skim milk will curdle more than heavy cream, and low-fat creams and cheeses are more likely to curdle than their whole-fat compadres.
- too high heat. Cream sauces must be cooked at low temps. Use a thermometer to ensure temperatures stay lower than 175 degrees F.
- too much acid. Cream should be added last (with exceptions like lemon juice). Wine can be very acidic, and should be reduced. any ingredients should be of medium temperature before cream is introduced, as it will separate at boiling.
How curdling occurs:
Dairy fats combine to form a rubbery mesh, which squeezes out water.
One possibility to prevent curdling is Carrageenan. There are three kinds, and Lambda Carrageenan is best for sauces because it is water soluble. It is derived from red seaweed. 80% of the world's supply originates from the Philippines, although its name originated from an Irish fishing village noted for a pudding made from seaweed and sweetened milk.
Interesting fact: Camel's milk will not curdle. It may be tougher to find on your supermarket shelves.
If a cream or butter sauce “breaks,” it can be fixed. In a separate pan, gently heat a small amount of your cream or your dairy base, and gradually add the broken sauce, whisking as you go. The added dairy fat plus the gradual temperature reduction will rectify the curdling. This is called “tempering” a sauce.
Or... remove the curdled sauce from heat immediately and place pan in an ice bath, which will immediately halt the cooking process. You may add an ice cube to the sauce as well. This quick-cooling should help bring the sauce back together. Some cooks recommend adding starch, such as a paste made from flour or corn starch and water.
None of these methods are foolproof, and many chefs will attest, sometimes you may have to just start over! C'est la vie!