Most recipes I've seen for making stock have you bring the ingredients to a boil and then skim off the foam, lower to a simmer and cook for a period of time.

This may sound like a stupid question, but: Why bother to skim off the foam?

Thanks.

I always assumed it was just to keep it from reentering the stock later.

But of course one could wait until after it's done cooking to take it off.

According to epicurious.com: "It is important to have a clean stock before you add the other ingredients, because the foam is impure and should not be cooked into the stock; if the stock is not clean before you add the herbs and spices, you will wind up skimming them off, altering the flavor of the recipe."

Also, if you don't skim off the broth, it can become mixed throughout the stock as it simmers, making the stock cloudy and unattractive.

Thanks, Kisal. I don't know what they mean by "impure". What IS the foam? Is it dangerous?

But it does make sense if foam prevents other ingredients from mixing well with the liquid. I also understand the visual aspect - if you're making consomme, or aspic, for example. You just can't beat a good aspic.

For other dishes that require stock, it doesn't seem important. I don't think I've ever made a clear stock. Or clarified a stock. How lazy is that?

No, not "impure" in the sense that it's inedible. IIRC, it is essentially protein and a bit of blood, primarily from the bone marrow and any uncooked meat that might be on the bones. I have made broth without skimming off the foam. I never let it boil, though, so nothing much in the way of foam develops. OTOH, I have also had my broth turn out very cloudy a few times. For most purposes, such as cream soups, that doesn't matter, but if you're using it to make a clear soup, such as Egg Drop soup, it is much prettier and more appetizing if the broth is not cloudy.

Also, I always add some skins from yellow onions (yes, the papery stuff you peel off! ) when I make chicken broth. It gives the broth a lovely yellow color. My grandma taught me that trick.

Great tip! I will try that. Do you ever use a mirepoix when making the stock?

I always toss some celery and onion in ... I save celery and onion trimmings (not the roots, of course ) specifically to add to broth. I just put it all in a freezer bag, along with the chicken bones and wing tips. I store the bag in my freezer, and when I'm ready to make broth, I just dump the contents of the bag into my soup pot and add water to cover. I usually add a quartered onion, too, with the skin. I don't add carrots anymore, although I used to. I actually don't notice any difference in the flavor of the broth when I make it without carrots.

Sometimes, if I feel like going to the trouble, I make a bouquet garni for the herbs and spices.

I'm a big believer in the health benefits of gelatin/stock made from bones. Save & add egg shells to boost the calcium content of your stock. Adding vinegar (which doesn't effect the taste) helps leach minerals into the stock.

I had never skimmed either, but I read recently about the need to do this (effecting taste I think) I could care less about cloudiness.

Actually, it is. In former, non-PC days, the stuff that floats was called what it is: scum. Not foam. Scum. Because that's what it is. An inedible mix of protein and blood that needs to be skimmed off in the first 10 minutes of the simmer/boil.

Do you need to bring your stock to a boil? Yes, you do. If you don't, the scum will simply cling to the meat and veg and later be impossible to remove. OTOH, once you've brought the stock (not broth - which should never be boiled and is NOT interchangeable with stock) to a slow boil/simmer, the scum will float up and be easy to skim.

Stock is what you make from meat, bones and veg. Broth is what you make from stock by reducing it slowly over time. Demi-glaze is made from broth by further reduction, until you have literally spoonfuls of thick, flavor-laden syrup with enormous concentration of flavor. It's very difficult to make a fabulous French 'Mother Sauce' without demi-glaze.

Here's how to make great chicken stock:


Enjoy!

Lisa

I've often asked myself this very question. I think it's just an aesthetic issue really. I don't care if my stock is cloudy. In fact, I have a feeling those "impurities" might be calcium and marrow from the bones, which is what I want to eat.


Why is it inedible when it is boiled but perfectly fine when eaten after baking, broiling etc? Something isn't adding up for me.

I've always found blood to be delicious. My Mom used to cook something, can't quite remember what, maybe liver, but it left a lot of blood behind in the pan that we both really relished.

For the same reason a lovely piece of fish or steak is delish when broiled - but disgusting when boiled. It has to do with what happens to protein strands when different forms of heat are applied to them.

That's why cheaper cuts of meat are tough as hell and virtually inedible when broiled/dry roasted, but delicious when braised for a long time in a liquid. Imagine boiling a crown roast or prime rib. Could you eat it? Well, it won't kill you if you gag it down. But why would anyone want to? Ditto for eating a 2 hour boiled egg. Or a boiled, rather than roasted bone/marrow.

How protein is cooked is crucial. That's why, btw, the chicken you use to make the stock is also 'inedible' and is usually tossed with the spent veggies. Since the chicken has been boiled rather than braised it's tough and tasteless. Could you eat it? Sure, but again - why would you want to?

This is why stock scum is inedible, and why it's skimmed. It has nothing to do with 'cloudy' stock, since skimming the scum off does NOT make a stock clear. Only clarifying the stock after it's done and the spent chicken, veggies and spices are removed makes a stock clear. There are several stages and methods for this, depending on the final product you desire. If it's demi-glaze, no need to do anything. Ditto for a stock to be made into a rustic soup at home, for instance, or used to make a sauce.

But if you want the stock for consomme or aspic you'll need to do several stages of clarification -- such as pouring the stock at least twice through many layers of cheesecloth, after which you reheat the stock, bring to a simmer, and add 2 egg whites.

As the whites cook and coagulate, they'll whisk up whatever impurities remain and float with them to the top of the pot, where they can be skimmed off. Could you eat the resulting protein mass instead? Yes . . . but I can't imagine wanting to do so.

Lisa

I don't believe that protein and blood are "impure" in the sense that they are bad for a person, or will cause illness, regardless of the method of cooking. For that matter, they are eaten raw in some societies.

I agree that it's simply a matter of aesthetics. The recipe I use for pate requires that the liver be boiled.

Ok, I'm making stock soon. I'll give the scum a taste when I make it and report back. If you don't hear from me, call 911.

Ok, reading my Harold McGee's, food scientist, book he says the scum are cell proteins that look like grey particles if you leave them in. Nothing about them tasting off.

Which makes sense. Cooking method has more to do with texture. For instance, if you boil fish it still tastes like fish but it'll actually dry out because getting it too hot causes those proteins to squeeze out water. Alton Brown show on poaching fish. Also, some of the flavor escapes into the water, thus kind of the whole idea behind stock...

McGee has a lot written on stock and says to be sure to cook it low and slow. Whole section on the importance of a cold start and uncovered, slow heating. The reason, the ugly proteins rise to the top and skim off easily. If you boil they remain suspended and get cloudy in the stock. IMHO, the scum might be nutrition I'd rather not discard.

I think the last time I made stock, I didn't bother with it. I didn't notice any off flavors, just a cloudy stock.

Another thing to consider is that the "skin" that forms on the surface of puddings is also protein, just like the scum on stock. The only reason it doesn't look "scummy" is because it's colored and thickened by the other ingredients.