are glucose polymers that are present in barley and malt. If not degraded during malting and mashing, they are carried forward into the wort and beer. Strictly speaking, glucans refer to any glucose polymer, although α- linked glucose polymers tend to be called dextrins. In brewing, the short- hand term “glucan” is usually meant to denote beta- linked (1,3, and 1,4) glucose polymers. Glucans are derived predominantly from the cell walls of the barley endosperm. During the malting process the cell walls are partially degraded to release beta- glucans. See malt. Enzymes that degrade beta- glucans are called beta-glucanases and are formed and activated during the malting process. However, these enzymes are very temperature sensitive and are readily destroyed in malt kilning and mashing. Gentle kilning and mashing regimes are needed to protect these enzymes. Excess amounts of glucans in wort can create problems in mash filtration, causing slow filtration rates and losses of extract efficiency. If carried into the fermenter, glucans can cause slow beer filtration. In the finished beer, they can cause hazes. See chill haze.