Why is it necessary to skim and strain stock?

[rayo de sol]

I am attempting to inexpertly make stock for the very first time. I'm reading the NT Beef Stock recipe on page 122 (although I'm making lamb stock), and I'm wondering if certain steps in the stock-making process are truly necessary?

Why do I have to skim the scum off of my stock after I bring it to a boil? SF just says "it is important" but she doesn't say WHY it's important. Can't I just leave the scum? I don't care if my stock has scum in it. I'm just going to be using the stock for cooking grains and beans.

Ditto on fat. Why is it important to refrigerate the completed stock and then remove the fat that congeals on top? Wouldn't any fat in the stock be an added bonus upon using the stock for cooking? I thought the NT philosophy was that the more animal fat we can incorporate into our cooking the better.

Thank you in advance to anyone who can clear up these stock enigmas for me!

[Vaquitita]

i believe the scum can give stock an off flavor. i've wondered about removing the fat too. but stock made from a whole chicken is very, very greasy. not necessarily palatable depending on what you're making. plus i think you remove some of hte fat so that you can use it for cooking other things.

[NoTiGG]

Originally Posted by Vaquitita

i believe the scum can give stock an off flavor. i've wondered about removing the fat too. but stock made from a whole chicken is very, very greasy. not necessarily palatable depending on what you're making. plus i think you remove some of hte fat so that you can use it for cooking other things.

I have always wondered this myself. I asked an old lady i know and she said it's important to remove the "impurities" . And so i asked her what impurities? If its particles from the bone... i think i want them in there! . If its just fat globules floating around (because fat rises) , then why not just be easy and finish cooking your stock... then refrigerate it to get it to rise quickly and congeal so you can skim it ?

I have however had some off flavored stocks........ and im not sure if this was because the bones were frozen before hand... it only seems to happen though when i use knuckle bones... it gives it this sharp medicinal flavor taste that isnt so well... not immediately but after hours of simmering.

So perhaps there is some truth to it I do not know.

[cobluegirl]

:

[desertpenguin]

i thought the scum was any accumulated toxins and they rose to the top??? idk...

as for skimming off the fat, i think that a lot of people don't particularly care for super greasy stock...and the fat can be used in other cooking, to fry in or to add some flavor to other things where you don't necessarily wish to use stock, and also to season cast iron...

[Leilalu]

Well I don't ever really get scum


AS for the fat, man I look forward to a bowl of noodles and fatty stock with veggies and soy sauce

I have heard the fat can add a protecting preserving layer to stock so that it keeps longer as well.

[tboroson]

Traditionally, (and I'm thinking classical french "traditional" here, not neccisarily "grandma" traditional), the scum is skimmed because it imparts an off flavor. Personally, since I do my stock in a crockpot, I can't skim. I don't find the flavor to be objectionable. It's strained for similar reasons: remaining food particles can taint the flavor, particularly as they're prone to decomposing quickly. Plus, for classical french usage, in which the stock may be greatly reduced for fine sauces, you wouldn't want those flecks in such a sauce. In fact, classical stock is frequently clarified with egg white, isinglass or other flocculants.

The fat is removed because it provides a nasty, greasy mouth-feel to your finished product. You can save the fat and clarify it for use in frying or other cooking.

[phroggies]

Part of the "scum" is albumin, which is a kind of protein. As far as I know, it's not bad for you, but [BIG SPECULATION MOMENT BY SOMEONE WHO IS TOTALLY UNQUALIFIED] I do wonder if it might bind with the minerals in the broth and make them less easy to digest. Whenever I read old stock recipes they seem to recommend skimming--and I'm not talking about fancy chef recipes here, just plain old peasant food. Since so much of TF cooking is based on the premise that there's a good health reason for steps that might seem superfluous to us, I'm going to continue skimming. That said, I don't do it very religiously. I just try to get the worst off when it first comes to the top, and then I forget about it.

[tboroson]

But, the albumin that forms scum is already coagulated. If it's going to bind to minerals, it will have already done so.

I'm not trying to discourage anyone from skimming When I make stock on the stovetop, I do. I'm just saying, I don't think it's a critical step. I think it's a matter of taste.

[quietserena]

Being the experimenter that I am, I tried it a few to not skim and every time the stock had an 'off' taste to it, kind of bitter.

[Leilalu]

Wel I personally leave the fat in as I like the taste. I also veiw it as a good way to get fat into my kids.

[phroggies]

Originally Posted by tboroson

But, the albumin that forms scum is already coagulated. If it's going to bind to minerals, it will have already done so.

That totally makes sense. . .

[pampered_mom]

As for removing the fat that congeals on the top...I was just reading something along these lines and remembering that I found it very intriguing. I can't for the life of me remember what that was, but if I find it I'll post back here. I do know that leaving the fat in the broth has a quality impact on sauces made from it...

ETA: I found it! It was posted to another list I'm on. You can read it at http://rachelernst.com/forums/forums/581/ShowPost.aspx