despumation

from The Century Dictionary.

• noun The rising of excrementitious matter to the surface of a liquor in the form of froth or scum; a scumming.
• noun The mechanical removal of scum or foam from a liquid by skimming.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of throwing up froth or scum; separation of the scum or impurities from liquids; scumming; clarification.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of throwing up froth or scum.
• noun Separation of scum or impurities from liquid; clarification.