Skimming soups and stocks helps keep the liquid clear and visually appealing. But what causes that gray foam, and how do you remove it?
When soups and stocks simmer, proteins and impurities rise to the surface and form a grayish foam or scum. Leaving this on the surface will make the broth cloudy and less attractive. Removing the foam is simple: stay nearby while the pot simmers and skim off the scum as it appears. After some time the formation of foam will diminish.
To make skimming easier, postpone adding vegetables until after you’ve finished removing the foam. Also maintain a gentle simmer rather than a rolling boil. A simmer encourages the impurities to collect at the surface where they can be removed; a hard boil can cause them to emulsify into the liquid and cloud the stock.
Here’s what it looks like:
Use a skimmer or a spoon to lift the foam away from the surface:
Collect the skimmed scum in a bowl and discard it. The result will be a clearer, cleaner-tasting broth ready for finishing or serving.
