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May 6, 2007 03:50 PM

Cheese sauce separates

I seem to be incapable these days of making a milk based cheese sauce, without the cheese separating as soon as I add to the thickened milk. I do the usual butter & flour cooked for a minute or two, then three cups of milk heated till just boiling and then thickened. The last three times I added the grated cheese (after I had taken the pot off the stove) it separated. I have good pots, so I don't get it. For the past year I have been using 1% organic milk - could that have anything to do with it (not that I could see how).

Please help!


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  1. You give specifics about everything but the cheese you use (1% organic milk, good pots, etc). What kind of cheese? is it grated or chunked? How much cheese is added?

    2 Replies
    1. re: Sherri

      I've used everything, from plain old grated kraft, to hand grated 5 year old cheddar or hand shredded mozza. I don't generally chunk it, but use it shredded. I've added the whole lot at once and put it in bit by bit, but it doesn't seem to make a difference.

      1. re: riverdale

        Cook the flour-butter roux until it begins to smell "nutty", add milk and stir to incorporate. Standard Bechamel calls for 1 TBLS flour and 1 TBLS butter to 1 C milk.
        Add a TBLS of some acid (I use Sherry) and stir in the cheese off heat. STIR is the operative word, do not beat.

        Some cheeses (Gruyere & Mozz are notorious) may string and this can be remedied by tossing the shredded cheese w/ a small amount of additional flour.

        Good luck.

    2. You might want to add the cheese slowly in batches - grated. I'd imagine it's a bit like making fondue. You slowly add more grated cheese in small batches as the mix becomes completely incorporated and melted.

      1. Darn it, that's frustrating. A couple of tips, and then a recent CH post.

        I sense the problem is instability in your white sauce. Make sure the amount of roux (butter and flour) is adequate for the amount of milk you are adding. Create stability in your white sauce by first cooking the roux to a blond stage (it will smell nutty if you get close) and then, adding the heated milk ladle by ladle and whisking after each addition. This helps create stability in the white sauce. Last, cook the white sauce on low for 5-7 minutes to further stabilize the starch/fat/protein/water mixture, whisking frequently till the sauce is thick and a bit glossy. Off heat, add the cheese handful by handful, stirring with a whisk after each addition to incorporate the cheese.

        Here's another recent post on the same problem:

        4 Replies
        1. re: maria lorraine

          thanks to all - I suspect that there are two problems - one is the switch to lower fat milk. The more important issue (having read the mac n cheese thread and these posts) is not cooking my butter/flour enough and perhaps not using enough flour. I may have eased up a bit on the flour to keep it smooth.

          I'll give it a go next weekend!

          1. re: riverdale

            Honestly, the lower-fat milk is not an issue. Riverdale, you "build" this sauce in a way and there is a process you must follow. First, you must have an adequate amount of roux (butter *and* flour, not just more flour) to the amount of milk. The stability and thickness of your sauce will be depend on this proportion. For a thin sauce it is usually one tablespoon *each* of flour and butter to every cup of milk; for a thicker sauce it will be two tablespoons each. You must cook the butter and flour together on medium-low heat more than a minute or two, about five minutes. This also prevents lumps. Your goal is to get the fat and the starch in the flour to link up on a molecular level -- and that takes more than a minute. When the roux looks an ivory color (what chefs call blond) and smells nutty when you get close, then you can whisk in a single ladle of already heated milk (that you have in a saucepan near). Once that is incorporated and the mixture thickens, whisk in the next ladle. Remember, you cannot add all the milk at once or you overwhelm the mixture and defeat your purpose. Step by step, a ladle at a time. Once all the milk has been added, reduce heat to low and cook the mixture for 5-7 minutes, whisking frequently, to give the starch molecules the time to grab onto all that liquid and hold it securely -- and when it's thick and glossy and absolutely smooth -- take the white sauce off the heat, and it will be happy to incorporate your grated cheese handful by handful. It's chemistry. You have to have the right proportions, and you can't rush the process.

            1. re: maria lorraine

              Maria - from reading your steps, I see at least one thing I've done right and three things I've done wrong. I have had 1 tbsp of flour and butter for each cup of milk (right), but I've only cooked it for a minute or two (mistake one). I've then added three cups of milk all at once (mistake two) and the milk has been cold (mistake three). Finally, I've often just ended up dumping in all the cheese at once after I remove it from the heat - not thinking about the chemistry of it all, simply thinking that it needed to be melted (not bonded - which seems obvious the way you've described it)

              Thanks - I feel that I should try this again tomorrow night!

              1. re: riverdale

                Good luck to you, Riverdale. I sure hope it's tasty. Let us know how it goes, and what you served the cheese sauce with, or on.

        2. You may also need to let your roux cook a bit longer to make sure that you've got the flour and fat well incorporated. You might also need to increase the flour in your roux a bit to make sure there's enough in there to help bind everything later on.

          1. What i do to keep the seperating from happening, is i melt the cheese, add the milk, and then mix some flour with milk to avoid lumps & then i add that to the mix. I also use then1% milk and it works ok following this method. I just wing the measurments.