YEAST

The substance produced during the vinous fermentation of vegetable juices and decoctions, rising partly to the surface in the form of a frothy, flocculent, and somewhat viscid matter, insoluble in water and alcohol, and gradually putrefying in a warm atmosphere. It excites fermentation, and accelerates the proce when added to saccharine and mucilaginous liquors. It appears closely allied to gluten; and, like that vegetable principle, it contains nitrogen as one of its ultimate elements. [s. 1351]