Stems are the rachis, or skeletal remains of a grape bunch or cluster after the grapes have been removed. Often during grape crushing the rachis gets broken, allowing bits of stem to remain in the must during fermentation. These bits of stem make up part of the cap in a red fermenter and part of the pomace after the new wine is drained from the tank. Generally, the stems in a fermentation are undesirable because they can supply "bitter" tannin to the liquid. This type of bitterness is difficult to remove by fining. See stalks. (Wine/Other)