http://chowhound.chow.com/topics/745141
what *is* that foamy scum on chicken soup?
ramonasaur Nov 5, 2010 the foam/scum that rises to the top when you make meat broth -- first feathery, then white and foamy -- what is it? where does it come from? why does it have to be skimmed off?
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Joel Nov 12, 2010 The scum is not just protein. The scum floats; protein is more dense than water and would sink. The floating stuff is coagulated (denatured) lipoprotein, the same "L" that is in the terms HDL and LDL (from your cholesterol workup).
Protein combined with lipid (fat) is less dense than water (the "D" in HDL and LDL refers to the density). When boiled, these lipoproteins coagulate and float. The scum tastes just fine to me, it's laughable to call it "impurities." All cells have lipoproteins in their cell membranes.
However, leaving them in will cause the stock to be irreparably cloudy in the end. If the goal is a stew, then who cares if the stock is cloudy. If the goal is consomme, then skim away.
I think there is a "Chinese cream stock" in which the items (pork, duck, chicken) are deliberately cooked at a rolling boil so as to incorporate all the flavors into the liquid. The result is quite creamy-looking. In this method the lipoproteins are physically forced into a colloidal suspension.
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amokscience Nov 12, 2010 Pros skim so your soup looks clear and 'professional'. The extreme case of scumming is a consomme where you try to get every bit of particulate removed so you have a crystal clear broth.
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sblimekyle Nov 12, 2010 If one really cares about professorial food preparation....a method taught at that up state New York chef school...place the pot half on the burner and half off...this will create a hot and cool spot where the proteins that coagulated will rise to the cooler side and solidify faster for easier removal. Then you can just use a ladle...instead of some crazy hair brained creation Mr Brown is so used to implementing ?? Also if you are interested in removing that oily residue...take tissue paper...not kleenex, and gently lay the paper on the top of the liquid and let the paper absorb the fatty oils. OH!!! and another thing...taste is most definitely affected by leaving this byproduct in your simmering liquid...This "SCUM" is the impurities of the liquid and its components...so if your palette goes unaffected by these impurities, then by all means leave them in...please try one way, then the other... If you can not tell the difference, then who am i to tell you what you like or don't like...if its tastes good to you then that is all that matters.
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cgarner Nov 5, 2010
It’s protein, quite simply, it gets churned about in boiling water coagulates from the heat and raises to the top (Alton Brown did a really good episode explaining it and compared it to the foamy clumps you see on the beach when it’s windy)
You don’t HAVE to strain it… if you don’t care that your soup will look swampy and cloudy with all matter of particulate floating around in it. It doesn’t affect the taste one way or another
what *is* that foamy scum on chicken soup?
ramonasaur Nov 5, 2010 the foam/scum that rises to the top when you make meat broth -- first feathery, then white and foamy -- what is it? where does it come from? why does it have to be skimmed off?
---------------------------
Joel Nov 12, 2010 The scum is not just protein. The scum floats; protein is more dense than water and would sink. The floating stuff is coagulated (denatured) lipoprotein, the same "L" that is in the terms HDL and LDL (from your cholesterol workup).
Protein combined with lipid (fat) is less dense than water (the "D" in HDL and LDL refers to the density). When boiled, these lipoproteins coagulate and float. The scum tastes just fine to me, it's laughable to call it "impurities." All cells have lipoproteins in their cell membranes.
However, leaving them in will cause the stock to be irreparably cloudy in the end. If the goal is a stew, then who cares if the stock is cloudy. If the goal is consomme, then skim away.
I think there is a "Chinese cream stock" in which the items (pork, duck, chicken) are deliberately cooked at a rolling boil so as to incorporate all the flavors into the liquid. The result is quite creamy-looking. In this method the lipoproteins are physically forced into a colloidal suspension.
-----------------------------------------------
amokscience Nov 12, 2010 Pros skim so your soup looks clear and 'professional'. The extreme case of scumming is a consomme where you try to get every bit of particulate removed so you have a crystal clear broth.
----------------------------------------------
sblimekyle Nov 12, 2010 If one really cares about professorial food preparation....a method taught at that up state New York chef school...place the pot half on the burner and half off...this will create a hot and cool spot where the proteins that coagulated will rise to the cooler side and solidify faster for easier removal. Then you can just use a ladle...instead of some crazy hair brained creation Mr Brown is so used to implementing ?? Also if you are interested in removing that oily residue...take tissue paper...not kleenex, and gently lay the paper on the top of the liquid and let the paper absorb the fatty oils. OH!!! and another thing...taste is most definitely affected by leaving this byproduct in your simmering liquid...This "SCUM" is the impurities of the liquid and its components...so if your palette goes unaffected by these impurities, then by all means leave them in...please try one way, then the other... If you can not tell the difference, then who am i to tell you what you like or don't like...if its tastes good to you then that is all that matters.
----------------------------------
cgarner Nov 5, 2010
It’s protein, quite simply, it gets churned about in boiling water coagulates from the heat and raises to the top (Alton Brown did a really good episode explaining it and compared it to the foamy clumps you see on the beach when it’s windy)
You don’t HAVE to strain it… if you don’t care that your soup will look swampy and cloudy with all matter of particulate floating around in it. It doesn’t affect the taste one way or another