the world > food and drink > drink > manufacture of alcoholic drink > brewing > [noun] > froth or scum (3)
The froth that forms on the top of fermenting malt liquors, which is used to leaven bread, and to cause fermentation in other liquors; yeast, leaven.
A yellowish substance produced as a froth or as a sediment during the alcoholic fermentation of malt worts and other saccharine fluids, and used…
the layer of froth covering fermenting beer.