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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.



    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.

              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.

                3. Since you quoted me I will reply, despite the fact that I am not a professional cook.

                  The fact that vigorous boiling emulsifies some of the fat in stock comes straight from Harold McGee and other reputable food scientists.

                  McGee: "A hot start produces many separate and tiny protein particles that remain suspended and cloud the stock; and a boil churns particles and fat droplets into a cloudy suspension and emulsion."

                  Shirley Corriher: “If you boil a stock vigorously, the fat
                  will emulsify or combine with the liquid and form a cloudy, fatty stock. Instead, you want the fat to remain separate and
                  float to the top so that you can remove every bit of it,”

                  eGullet "Science of the Kitchen: Cooking Meat" "However, vigorous boiling will emulsify the fat into the stock, which creates a cloudy stock. Besides, fast boiling is only a few degrees above a gentle simmer. Thus the traditional advice to make good stock is to do so at a gentle simmer for a long time. "

                  Ruhlman (not a scientist, I know): "A stock becomes cloudy if you simmer it too hard and emulsify the fat into the stock. Trying boiling chicken bones and scraps really hard for an hour. It will look almost creamy."


                  A simple google search will turn up a lot more information on the subject.

                  Plus I've screwed up making stock more that once and can attest to this personally.

                  2 Replies
                  1. re: C. Hamster

                    Sorry, by the way. In another thread I saw you write something along the lines of "This was our first lesson in cooking school: Learning proper seasoning of chicken...", so I took it you were formally trained.

                    1. re: Grunde

                      You are right, I attended culinary school but I'm not a chef. :-). Long story....

                      I forgot to say that your English is perfect!

                  2. Yeah, my thought is make two pots of stock, boil one hard and gently heat the other.

                    IME, the more rapid boil produces cloudy stock.

                    1. I'm one of those that believe that there is some emulsified fat in a stock that is at a hard boil. I believe this due to reading science-based explanations written by food scientists.

                      While it may seem obvious to you that the cloudiness is caused entirely by protein and not fat, I'm afraid that is not a scientific exploration of the issue. You may, indeed, be right, but there is nothing to back that position up. It employs the same type of reasoning as the old wive's tale that you're attempting to debunk.

                      Cloudy stock *generally* does not clarify simply by allowing particles to settle. Were that the case, no one would worry much about a cloudy stock at all. In addition, no kitchen would waste the time and ingredients in making a consomme if all they had to do was let it sit on the counter for a little while. In addition, I have not noticed that behavior in my over-boiled stocks in the past. I also use a pressure cooker now and haven't had that problem in a long time, though.

                      You're right. There is no theory that magically causes fats to emulsify at 100 degrees. However, at a roiling boil there is enough turbulence to provide the agitation necessary. Even in your example of a homemade vinaigrette, you can't make the emulsion between the oil and vinegar if you don't have:1) an emulsifier and 2) agitation.

                      I do believe that much of the cloudy appearance is due to albumin proteins that get agitated and emulsified into the stock. Were it only appearances, I might not even care about a cloudy stock. What I object to is the dirty, greasy taste of a poorly made stock. I do believe that taste comes from both proteins and fats that get emulsified at temperatures high enough to cause significant turbulence.

                      That said, again, you may be right. I'm taking my information from Harold McGee and other food scientists for the time being, though, and they report that fat is definitely part of the mixture in a cloudy stock. I'm going to stick with the prevailing opinion among food scientists until someone shows that theory is flawed via a well-designed experiment.

                      I like the questions that you bring up and I would like to see someone put the question to a fresh test to see if we have been passing around poor information.

                      8 Replies
                      1. re: cacio e pepe

                        This is indeed on very interesting thread. I'm learning a lot here.
                        In your opinion, what are the major mistakes people make when producing stock, and what characterizes poorly made stock?
                        Ps: The main lines, please. I'm aware that the whole area could fill books. Book references will do nicely too.

                        1. re: cacio e pepe

                          An very well explained, by the way..

                          I do agree entirely, although the presence of fat emulsified inti the stock was new to me, and counterintuitive at first thought.
                          But you and other writers now having driven this point home so forcefully, I'm happy to reverse my view on the matter. If things change, I change my my opinion, so to speak.

                          I have read McGees On Food and Cooking, but I can not remember him mentioning this, nor can I find anything about it neither under "stock" nor "emulsions". That said, it is an older edition.

                          1. re: Grunde

                            McGee, Keys to Good Cooking p 312
                            "Bubbling clouds the stock with tiny particles of protein and fat; gently moving water allows the particles to cluster and either rise to the surface or fall to the bottom. The open pot cools the stock surface, dries the protein scum, and begins the concentration process."

                            And as noted in the Serious Eats piece "For a neutral white stock, blanch raw meat, bones, and skin to remove off flavors and reduce clouding" and "soak bones in cold water to remove blood".

                            Under clarifying consumme by letting stock drain in the fridge: "collect the stock liquid that melted and dripped out of the intact gelatin network, leaving fat and protein particles behind".

                            While he talks about 'fat and protein particles', he does not mention an emulsion. There is an important distinction. An emulsion would have small fat globules surrounded by water, with some sort of emulsifier forming a single molecule thick later between the two liquids. Mayo is mostly oil droplets, with just enough water to keep them separate (adding some water can actually stabilize mayo).

                            1. re: Grunde

                              It's in ch.11, "Sauces" in the section "Meat Stocks and Sauces" just after "The importance of a cold start and uncovered slow heating."

                              Can't give you a page as its on my Kindle.

                              1. re: C. Hamster

                                Thanks. Which edition do you own? Mine is first or second, and I've heard the whole thing was reviewed at one point.

                                1. re: Grunde

                                  I have the 2nd edition (2004). I have the first around somewhere ... Haven't seen it for a long time.

                                  And, for the record, my point is not that the emulsified fat in boiled stock alone makes it cloudy. The particulate matter obviously makes it cloudy, as anyone whose made consommé can attest to. But, like McGee says, the mechanics of a hard boil churns the particulate matter into a suspension.

                                  And no, don't boil coq au vin. Boiling is the kiss of death for poultry. It renders it rubbery and unappetizing. And don't cook it for hours and hours either. Braise it covered in a slow oven for an hour or two (some recipes call for shorter than that).

                                  1. re: Grunde

                                    My 1st edition of F&S only has one paragraph on stocks.

                                    HM describes 2 types of emulsions. One that I was thinking about consists of many small drops of, say oil, immersed in another medium, say water, with small-molecule emulsifiers forming a thin coating on the drops, keeping them from coalescing.

                                    In the other, large molecules like gelatin form a mesh that traps droplets (and other matter). In chilled stock, that mesh traps the water component as well.

                                    1. re: paulj

                                      That's the one. That's excactly what mine says too.

                            2. I am no scientist, but have made many pots of chicken and beef stock in my day. I don't boil the stock, merely simmer it. BUT, the one and only time I got a cloudy stock was when I put in too many veggies in proportion to the meat and bones. I was just beginning to cook stock and thought that more veggies meant more flavor. WRONG! The other weird thing that happened was that the color of the stock was definately in the green shade, as I had used lots of celery and parsley.

                              1. http://www.seriouseats.com/2012/02/ho...

                                You are partially right. It is mostly not fat that is causing the cloudiness, but you can make a rather stable emulsion with gelatin where the particles do not fall to the bottom.

                                1 Reply
                                1. re: jaykayen

                                  His theory, which he thinks the experiment supports is that:
                                  "Well, my theory is that in the case of tonkotsu broth, the gelatin created as the broth cooks acts as a kind of net, trapping all that good stuff and causing the broth to become both opaque, and more flavorful. "

                                  If my memory is correct, stock made from feet (pigs or cows) is not only stiffer, but milkier in appearance.

                                2. My personal experience, not based in a science claim, is that hard-boiling a stock can create a cloudy mixture that will not separate later into a fat layer at the top after cooling. Two instances come to mind. One was a turkey (or maybe chicken) stock that boiled vigorously for a long while, and it never would clear up, and it was also quite greasy. The other has to do with fish stock: I had a bouillabaisse recipe that actually insisted that you hard-boil the fish stock, precisely in order to emulsify the fish fats into the stock. Of course, because the fish was less fatty to begin with than beef, the effect was more palatable.

                                  2 Replies
                                  1. re: Bada Bing

                                    the melting point of the fat affects how palatable an emulsified mixture of fat and stock is. In my experience, lamb has the highest, above mouth temperature. beef next, pork next, chicken and fish lower. Part of the lusciousness of butter, chocolate, lard, and duck fat has to do with their melting around mouth temperature.

                                  2. I can buy that a stock kept at a furious boil could emulsify fat...but who does that? (okay, there's noobs out there, but really....)

                                    I can also buy that **some** fat gets emulsified, even at a simmer.

                                    But I'm just can't go with "all cloudiness is emulsified fat" -- that one just doesn't fly.

                                    (especially when there are similar articles talking about how roasted/cooked bones produce cloudier broth than starting with fresh....)

                                    and egg whites still aren't grabbing fat...they're grabbing particulate matter.

                                    10 Replies
                                    1. re: sunshine842

                                      1. Lots of busy people can let a stock bubble enough to create cloudiness. It won't get tonkotsu-cloudy unless it's vigorously boiled for a long time, but even 20 minutes or so can create a cloudy stock. That can easily happen if a home cook gets distracted with other things as they are bringing a stockpot up to temperature. I don't think the boil need be all that furious to cloud a stock.

                                      2. Possible at a simmer. Less likely, though. It's unlikely that one could make an emulsified vinaigrette with very light agitation, though some emulsification could presumably occur.

                                      3. I don't think anyone made that claim. The OP claimed there was *no* fat in the cloudy stock. Some of us say that there is *some* fat in the stock and the fat can lead to an "off" flavor. At least it can create a flavor I find objectionable. But I love tonkotsu broth, so go figure!

                                      4. I'm assuming that when you mention egg whites you're talking about the egg whites and lean proteins used to create a raft to clarify a consomme. I also agree. I don't think anyone mentioned that the raft was used to grab fat. But I think the OP brought up the idea that cloudy stocks eventually just settle. I was dubious of that and cited the use of rafts to clarify consomme. If time to settle was all that was needed then why do we use a raft to clarify?

                                      5. I don't know the articles you're talking about re: fresh versus roasted bones. But fresh bones are generally first blanched and then washed, no? That blanching and washing takes care of almost all of the albumin proteins. Roasting cooks those albumin proteins and they are skimmed as they rise.

                                      I think why I like this nerdy discussion is because it's bringing in information that is new to me. I'm trying to integrate it with my experiences and what I've read.

                                      As I understand it, stocks get cloudy because of albumin proteins on the meaty bones being used. Period. They are the cause. And they also are what primarily lead to the cloudy appearance.

                                      But the whole picture is not so simple. Because those proteins can be amphipathic, those albumin proteins that are clouding the stock can also interact with the fats in the meat. When they do, they can cause the fats to emulsify with the stock. The fats will then never separate by rising to the top and therefore can never be fully skimmed off.

                                      In the end, I don't know that all cloudy stocks taste bad. I just know that the few times that my stocks came out a little cloudy were the few times that my stock tasted . . . well . . . kind of dirty. Just . . . wrong. If this were just a matter of aesthetics, I would probably be much less interested

                                      1. re: cacio e pepe

                                        I tend to make stock with pre-roasted/pre-cooked carcasses, just because I keep the carcasses when we're eating a chicken for a different kind of meal (there's usually a second bag in the freezer of wing tips, necks, etc., etc., )

                                        So my stocks tend to be cloudy -- once in a while I'll clarify if it's extremely cloudy, or if I'm using it in a recipe where it needs to be clear for one reason or another -- but overwhelmingly I'm adding other vegetables, the cooked chicken, noodles/rice/barley, etc. -- so cloudy makes no difference whatsoever.

                                        I can't say I've ever managed to turn out a batch of "dirty"-tasting stock -- water, perhaps, underseasoned once in a while, but never "dirty".

                                        I do, however, keep it to a barely-bubbling simmer -- I've made stock in the pressure cooker a few times and don't care for it -- so I make stock on days when I'm going to be hanging around the house all afternoon, anyway -- so the stock doesn't boil for more than 2-3 minutes when I'm bringing it up to temperature, but it then barely simmers for several hours.

                                        1. re: sunshine842

                                          I think cloudy stock tastes off. A little greasy or dirty. That's me though. And I LOVE my stock from my pressure cooker. Different strokes, it turns out.

                                          1. re: cacio e pepe

                                            but my stock is never, ever greasy - cloudy or not.

                                            1. re: sunshine842

                                              I would never dare say your stock is ever greasy. :)

                                            2. re: cacio e pepe

                                              All hail to the pressure cooker! :)

                                          2. re: cacio e pepe

                                            Ha, ha, ha...! Yes, this IS a nerdy thread, but I find it extremely informative.

                                            Two questions:
                                            a) Does these albumin proteins affect the taste on it's own, or just in emulsion with fat?
                                            b) Anyone care to enlighten me on this tonkotsu brothy thingy? It sounds intriguing. I used to make a lot of japanese, right after my italian period (1999 usque ad medium 2003).

                                            I actually lived in Kyoto for a summer way back, attending language courses and learning how to make sushi and various traditional dishes. I still have periods when I crave Nattoo on Udon Noodles.

                                            1. re: Grunde

                                              Do some search on David Chang and Momofuku. US PBS has aired a series called Mind of a Chef featuring Chang on various subjects, but ramen and ramen broth is a particular favorite. I've seen most of the episodes online, but others have said they can't see them outside the USA.

                                              1. re: paulj

                                                Yum, that's where I'm eating this weekend !

                                              2. re: Grunde

                                                Yeah, me too.

                                                a) I'm not sure, and I'm not sure of a good way to find out. My guess is that it's both. It seems to me that the scum that is skimmed off a properly simmered stock is similar to the albumin that's stirred up by vigorous boiling. In a simmered stock, the extra albumin never gets disturbed enough to float or enter into suspension. In a boiled stock I guess it would. Add in some fat with that stuff and I think together it creates something I object to.

                                                b) I think a poster shared a link to an article detailing that kind of broth. Basically, it's the anti-Escoffier method of stock. Vigorous boil for nearly a full day. Milky broth with full emulsification. And it's incredible! I have no explanation for it.

                                          3. I’m having so much fun! Thank you all for the lengthy and informative replies. It brings on a heap of new questions on my part, but I’ll have to start up new threads for some of them so that this one doesn’t become too extensive.

                                            To be honest, I was actually on my way to deleting my profile after the first day here. I thought this was just another of those forums where self-declared foodies are throwing around old kitchen myths and recipes for pot-á-feu in a micro (or wild theories about stock making).
                                            I’m so happy I was wrong. There are clearly many well read and knowledgeable cooks in here. I have been looking for a forum like this for a while.

                                            I thought I hadn’t had problems with greasy stock before, but that might not be true seeing everything in a new light. I have certainly experienced problems with clarifying some batches of murky stock on a couple of occasions. My grandmother told me to never fast boil a stock at a very early age, so I almost never have.
                                            On the other hand, I have offered to clarify other people’s stock/soups and been unsuccessful. Last time was a traditional meat & vegetable soup made on bones from salt-cured mutton legs (a Norwegian west coast specialty). The soup did taste dirty and now I understand why that wasn’t my fault. The problem was aggravated by the fact that some of the fat on these bones is highly oxidized and should be removed entirely. Having that actually emulsified into the stock was not a good thing.

                                            I have also done a couple of unsuccessful attempts at clarifying meat gels. I always pour on another couple of liters of water on the remnants to extract every last piece of goodness, and boil it down to a gel. I haven’t been super picky about removing all the fat from the surface before boiling it down, but I certainly will to that from now on.

                                            But now that I’m aware of this potential hazard, I’m starting to wonder what consequences this has for the humble stew. Many cooks (including me) would happily leave any stew, say a Coq au Vin, to boil for hours. The only logical conclusion seems to be that this would cause a lot of emulsified fat in the dish making it too “greasy and dirty tasting”.
                                            Would my Coq au Vin actually be immensely better if I popped the whole pan in the oven on 90 degrees for a couple of hours?

                                            1 Reply
                                            1. re: Grunde

                                              Coq au Vin doesn't matter that much -- you aren't EVER going to have a clear sauce, no matter what you do. And in a dish like this, having the fattier mouthfeel isn't a bad thing.


                                              You wouldn't typically boil CaV anyway -- it's a braise, so low and slow is the rule of thumb. Keep it at a slow simmer (you want some regular bubbles), but things like coq au vin, pot au feu, bourgignonne (and any other similar long-cooked dish) shouldn't ever be cooked at a boil, anyway. (it's pretty common to crank the heat up to get things started, but as soon as the bubbling starts, you turn it down!)

                                              You also have the extra process for many long braises of either dredging the meat in flour before browning, or starting the whole process with a roux -- a mixture of fat and flour, cooked until it thickens and begins to brown. The presence of the flour is always going to change the character of the dish from having a broth to having a sauce. BIG difference.

                                              Coq au Vin is also typically made from an old bird -- tougher meat that requires longer cooking, because there's more connective tissue than in a younger bird. This is okay, though -- slow braising breaks down this tissue, giving you a velvety, fabulous **sauce** -- again, not a broth.

                                              Poule au pot or pot au feu, however, have clear, unthickened liquid in the pot....these will be more susceptible to the emusion issue...but again, they shouldn't be cooked at a furious boil, either....a slow simmer for a few hours is best.