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Nov 30, 2009 08:44 AM

Cheese sauce/soup

Hi everyone! I'm so looking forward to your help.

I made a baked mac-n-cheese last week that was wonderful, but I think I melted the cheese in at a temp that was too high and it was a bit grainy.

Tonight, I'm planning a loaded baked potato soup that will need some sharp cheddar melted in and I'm wondering if there are any tips that you can offer for melting the cheese in so that it stays smooth. Do soups work the same as sauces?

Thanks for your help!

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  1. Grate the cheese and add it last. Turn off the heat before adding the cheese, and stir continuously until it melts.

    1. Graininess meant that your cheese curdled.

      Soups do work the same as sauces, although, because they tend to be less thick, curdling is of a greater concern. The following list is by no means comprehensive, but here's a few ways to prevent curdled cheese soup/sauces. I really detest curdled cheese sauce so I normally incorporate all of these suggestions when preparing a recipe.


      As Pikawicca mentioned, turn off the heat before adding the cheese. A cheese sauce should never boil.


      An all cream soup/sauce base pretty much guarantees that the cheese will not separate, but it also has a tendency to mask flavors. Whole milk requires starch (bechamel). Never use anything less than whole milk with any cheese other than American.


      It's always a good idea to start a cheese sauce with a roux/bechamel. Dissolved starch is vital to prevent curdling. The flour in bechamel is ideal, but other starches will fight curdling as well. Corn starch, arrowroot, potato starch. I don't know how your soup is prepared, but if you blend some of the cooked potatoes into the soup, that will go a long way to prevent curdling. Like the cream above, though, starch has a strong tendency to mask flavors, so you want enough to prevent curdling, but not too much.

      Water content

      I haven't seen any studies on this, but, from personal experience, the more water a sauce/soup has, the more propensity there is for curdling. If your soup is not that thick, I'd make a thick bechamel based cheese and add it separately.

      Fresh Cheese/Fresh Milk

      Old cheese that's been in the fridge for a while, even if it's not moldy, tends to be denser/harder to melt. The harder a cheese is to melt, the more propensity for curdling. Sometimes grating the cheese very finely helps, but not always. When making the bechamel, older milk will curdle easier, so make sure that's fresh as well.

      Processed Cheese (Sodium Citrate)

      The cheese in American cheese slices is altered chemically so that it's extremely difficult to curdle. When added to a soup/sauce, it not only prevents itself from curdling, it helps other cheeses from curdling. You can't use too much or it becomes a salt fest, but a slice or two in cheese sauce goes a long way.

      Lastly, it's always a good idea to grate your cheese. The finer the better.

      6 Replies
      1. re: scott123

        Scott!!! I'm so happy to see your post...I actually almost posted to an old thread that I found where you "taught" at length about cheese sauce and the science of dairy cooking in general, but when I saw that it was from 2007, I thought I might should start fresh!

        Here's what I was thinking for the soup:

        soften diced onion and some minced garlic in bacon grease (hold on...had to go wipe my mouth) being careful not to add the garlic so early that it burns...

        add flour and xtra butter (if needed) for roux over the onions cook that for a bit...not sure how long...

        add in 2c chk broth, 2c water (might not be a good choice for soup with cheese as your post mentions water content might be a culprit) and let simmer about 20 minutes

        add 1/2 of the baked potato flesh and all skins and some roasted baby carrots and puree until smooth

        Off heat:

        whisk in 1/2c 2% milk (all I have tonight), 1/2 c cream, 1/2c sour cream

        whisk in 1c of shredded sharp cheddar (again, all I have tonight)

        and when that is incorporated, add other 1/2 of the baked potato flesh diced and some chopped up bacon

        serve up and garnish with sour cream, more cheese, green onions and maybe a little bit more bacon.

        *disclaimer: I am a total novice and sort-of derived this recipe on my own. Please feel free to teach/tweak as your experience deems necessary! I'm so excited!

        1. re: AChieffe

          I was with you right up until the second addition of the "other 1/2 baked potato"...this may be a problem as you have already added your cheese and therefore can't afford to let the mixture boil whihc may be a challenge for heating up your potato...can you reverse the order of the cheese/second half potato? or perhaps just ensure your potato flesh and bacon is hot but not boiling?

          1. re: LJS

            well...the potato and bacon are already cooked...I'm just adding them back in for texture. Will it be okay? I don't plan to let it boil.... : /

          2. re: AChieffe

            AChieffe, my apologies for the delay in getting back to you. At this point, I'm sure the soup has already been made, but, for future reference, I did notice one ingredient that could be problematic- sour cream. Acids are the kiss of death when it comes to curdling. I wouldn't just add the sour cream last, I'd add it after the soup has cooled to just above serving temp.

            Other than that, I think you're in good shape. Between the roux and the pureed potato, this soup has plenty of starch. You might be able to get away with just the starch from the blended potato, but until you've made it a couple times, I wouldn't take the chance. The milkfat from the cream should help as well. It might not hurt to hold back on the water until after the cheese is melted. At the point where you add the cheese, you want the consistency of a sauce.

            If you add the garlic before you add the flour, by the time the roux is done (about a minute on low heat for a white roux), chances are it will be overcooked. Sauteeing garlic should only be a matter of seconds- if the garlic takes on color, you're asking for trouble, imo. Personally, I've stopped sauteing garlic completely. I find a 20 minute simmer is more than enough to soften garlic's harsh tones.

            I'm a bit of a purist when it comes to roux. As you saute onions, they'll weep less and less liquid, but, by the time you add the flour, they'll still be giving off some moisture, which might cause clumping. It's probably overboard to do the roux separately from the onions, but you might want to extend the simmering another 10 minutes just to be safe.

            Lastly, I'm not sure how often you work with onions, but, before you add the flour, taste them and make sure they're actually soft. Onions have taken a very fibrous turn in recent years and can take a lot longer than expected to soften. Crunchy onions might work well in some dishes, but I think they'd be really out of place here.

            Other than that, this recipe looks like winner. It's almost identical to a broccoli and cheese soup that I do.

            1. re: scott123

              I did make it last night and it came out GREAT! We loved it so very very much. The only complaint that I had was that it was not as hot as I'd have liked.

              It's funny you mentioned the sour cream b/c I had 4 tubs that I need to use so that's the ingredient I searched when I found my jumping off point for this soup because it used a bunch of it.

              I think next time I make it, I'll make a traditional bachamel cheese sauce in a separate pan and then add THAT to the potato/broth/water mix. I think that'll help with the temperature and the cheese melting and I won't have to worry about it. Plus, maybe it won't take as long to make since I can do the two parts at the same time. Is this a good idea or overkill?

              1. re: AChieffe

                That's how I do cheese soup. Overkill is my middle name, though :) I'll do just about anything to make sure curdling doesn't occur.

        2. Hi
          I made a roux and melt the cheese in the roux and never had a problem
          Also , I frequent a restaurant that has the best nacho's and cheese, it is like a cream sauce and it is poured over the naucho's so each one has it's own cheese..
          I asked the chef how he makes this and he said to just add heavy cream to the cheese and melt it down at a low temp. I tried it and have been happy ever since. I now make them at home. Anyway the point is you can use this same concept for your loaded backed potatoes. yummy