Adding acid to cream sauce
I tried adding some lemon juice (half a lemon) into my creamy pasta sauce (butter, heavy cream, etc.) and it all separated and curdled. Is it because I added too much lemon juice? Or that I'm supposed to add in the lemon juice after taking the cream off heat? Thanks!!
Not sure about cooked cream sauces... but when I make Chiles en Nogada... I typically add Lemon juice to sharpen the flavors (Crema, Almond Butter, Lemon Juice, Nutmeg, Salt)... uncooked.
Heavy cream is far more stable than milk, but it still can be curdled under the right conditions. Heat is a factor in curdling- try adding the juice off the heat. Better yet, though, if you want the taste of lemon in a dairy based sauce, use zest. Cream can be boiled with zest and it won't curdle.
A great way to add that lemon zing (besides using zest as already noted, to the sauce) Is to toss the *pasta* with lemon juice after draining. Try it, you will like it!
Acid curdles dairy. That's straight chemistry. If you want to make it a feature and not a bug, you need to use something that responds well as well as other ingredients.
My mother's recipe for lemon bay cream sauce requires a can of canned milk, a pat of butter, flour, onion salt, a bay leaf and lemon juice. Basically use the butter, flour and onion salt to make a roux. Thin the roux into a thin white sauce with canned milk. Simmer the bay leaf in the sauce. Just before serving, add the lemon juice and stir like crazy so the curdling only thickens the sauce rather than clumping. I think having the flour making it an emulsion keeps the milk from completely curdling, which is of course the process of separating into curds and whey.
Or you can simply use sour cream instead of cream and lemon juice.
Have you tried thickening the cream and butter with cornstarch first and then adding the lemon juice?