Do you have to skim the scum when making yummy healthy broth?
If you’ve ever made stock or broth, you know what I mean when I talk about “scum”.
You turn on the heat, the pot heats up, and it’s not long before all that whitish, greyish, or brownish foamy “scum” rises to the top of the pot just as it starts to simmer. What is that stuff, anyway?
Broth scum is simply denatured congealed protein. It comes from the meat, not the bones. It’s not gelatin, which dissolves. It’s mostly the same proteins that make up egg whites.
It’s harmless. It’s flavorless. It’s perfectly fine to eat and probably shouldn’t be given such a derogatory name. Maybe we should call it bone foam or protein puddles or broth clouds instead.
So… why skim the scum?
Some people think it looks gross and just need to get rid of it. Some people do it because of tradition - it’s what their mother and grandmother did. Some people do it because basically every recipe on the internet tells you to do it. And some people do it to achieve a “refined” culinary dish.
If you leave the scum, it will break up into microscopic particles and disperse in your stock, making it cloudy. Straining later, even through layers of cheesecloth, won’t remove it. Once it boils, the scum is there to stay. Cloudy broth is the worst case scenario, and, in my opinion, it really isn’t that bad.
If you skim the scum, you need to do so with a while the broth is simmering, before it boils. The boiling is what breaks up the particles and mixes it up in the pot. If you skim the scum, the end result is a clear broth.
Culinarily, skimming scum to achieve a clear broth is treasured. And it’s really all about the aesthetics.
For darker, heartier dishes like beef bourguignon or minestrone soup, clear broth won’t make a difference. But, for lighter dishes like Vietnamese pho or a chicken noodle soup, clear broth can make a nicer looking bowl.