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The mystery of the cloudy stock

Hi everybody.
I'm new in here, but I have read some advice in this forum that strike me as novel to say the least.

In several discussions about making stock from poultry it is claimed that one should never hard boil stock because it will get cloudy.
Well so far so good.

The interesting part is that many seem to believe that this cloudiness is caused by the fat emulsifying into the stock. Even some people who claim to be trained professional cooks writes things like

"You dont boil stock because that emulisifies the fat, making for a greasy product. Its not about the protein.".

I cant see any scientific argument for how this could be true.
To me its pretty obvious that the cloudiness is purely caused small fragments of proteins, meat and other impurities stirred up by the boiling.
a) If the cloudiness was caused by emulsified fat it would eventually rise towards the top when left alone (like in a home made vinaigrette). This does NOT happen.
b) When leaving cloudy stock alone in room temperature, the cloudy stuff tends to collect at the bottom - indicating that the cloudiness is indeed caused by heavier solids, not fats.
c) There is no known theory that indicates that fat would magically start emulsifying into the stock when the temperature changes from 99 to 100 degrees Celsius. (If so, wouldn't pressure cooked stock emulsify entirely?).

I can only conclude that the emulsion theory is an old wive's tale.
Cloudy stock is in most cases caused by

Any thoughts on this?

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  1. As a pressure cooker expert, I can confirm that pressure cooker stock is clear because of the reduced "motion" of the stock.

    Contents in a pressure cooker only "boil" - that is the contents move around and bubbles break to the surface- when the cooker is reaching and loosing pressure (about 10 minutes each). During the whole cooking time under pressure the contents of a cooker are eerily still, though the pressure and temperature are squeezing the juice out of the solids.

    Ciao,

    L

    1. I've never heard the emulsified fat theory -- but I'm with you -- you can see the little particles and such.

      I'll also offer up the whole process of clarifying with an egg white...there is no way to make emulsified fat cling to a cooked egg white -- if cloudiness was emulsified fat, you couldn't clarify it by dropping a beaten egg white into the stock.. It has to be other particulates.

      1. I totally agree with the both of you. That's why I was a bit perplexed when I read the post from all the emulsion theorists, like here: http://chowhound.chow.com/topics/8852...
        (read posts from Jan. 11 and forward

        )

        This must be a truism going around among home cooks.

        I use a pressure cooker for all my stock too. For a long time I didn't, mainly because Julia Child told me not to. But after seeing Heston Blumenthal recommending it i reckoned it was ok.
        It tastes wonderful and seems more aromatic. It saves a lot of time an energy too and, if done right, comes out clear as boullion.
        I guess it must have been those old time rubber seals that gave Ms. Childs stock "that characteristic pressure cooker taste".

        1. Read this. It will settle this once and for all. You got your fat and your water and all you need to emulsify them, in our case to make a cloudy stock is some protein which we have hanging off the carcass. As soon as the heat gets high enough all three bond together. Adding vinegar (acid) just adds to the emulsion process. Make mayo? What do you use to help emulsify the oil and protein in the egg yolk? Some type of acid.http://kitchenscience.sci-toys.com/Em...

          1. Unfortunately I can't read the site since my browser bounces the link as malware.
            However: I can not see how "I have everything I need to emulsify the fat and stock".
            For that you would need an emulsifier, and even though protein can work as such, it's not even nearly concentrated enough to form any permanent emulsion.

            I'm not sure I understand what you mean by "What do you use to help emulsify the oil and protein in the egg yolk". Maybe oil and proteins can emulsify too. But when people talk about emulsion, in 99 percent of the cases they mean emulsions between polar and non-polar liquids like water and fat.

            Egg yolk is and emulsifying agent on its own, caused by it's high content of lecithin. (Another well known emulcifier used in cooking is lecithin from soy beans.)
            The goal when making mayo is to bond the yolks and the oil. You certainly don't need any acid to do that.

            6 Replies
            1. re: Grunde

              Gelatin is an emulsifying agent. Pil pil is a Spanish emulsion that relies on the gelatin from the fish.
              http://spanishfood.about.com/od/fishs...

              I just warmed a cup of home made chicken stock with fat (about an 1/8" thick layer, and whipped it with the immersion blender. The result was milky white, not the semi-translucence of the cold stock. I'm going to let cool and see how well the fat separates out. Oh, and that foamed stock tasted just fine, maybe even a bit more flavorful than the fat free stock.

              To properly test this I should also whip some of the stock without any fat, and compare the two.

              As I wrote on the other thread, I don't normally boil my stock hard, but I don't take special effort to prevent boiling, especially when I cover the stock pot. For the hearty soups that I make, cloudy stock is no big deal. And I've never thought of my stock as being 'greasy'. Oil droplets may be part of the cloudiness, but it's not an objectionable part.

              1. re: paulj

                This whipped stock solidified much as the regular stock did, complete with a distinct fat layer on top. But both parts remained milky white.

              2. re: Grunde

                Okay everybody, I wrote this when I hadn't eaten for a while, so sorry if i came across as a bit hostile. As I wrote in another thread: I'm from Norway and my English isn't great. If I write something offensive, I generally don't mean to - unless I'm very obvious of course... No really, I never mean to, almost...

                Anyways, this actually turned out to be a very interesting discussion. I'm not going to try to prove my point agains better knowledge here. I'm always willing to learn something new. It's just that I have NEVER experienced an emulsifying stock before.

                1. re: Grunde

                  I don't think you came across as hostile, just skeptical.

                2. re: Grunde

                  ... and I'll write a longer answer later. I guess I have to read my McGee a bit closer.