Cellulose is the most abundant organic polymer on earth, and the primary content in a beer’s trub. Cellulose is unfermentable, tasteless, and odorless. It is a solid, and much of it will drop out of the beer during primary fermentation, where it sinks to the bottom of the fermenter and helps to form the trub bed. The primary contributors to a beer’s cellulose content are fibrous materials like grain husk and hop leaf.