Amylose. The sugars in wort are derived from the breakdown of starches contained in malt and any adjuncts that may be used in the mash. Starch can be separated into two parts, amylose and amylopectin, and these two different types of glucose polymer are synthesized simultaneously and then incorporated into the starch granule in very different ways. Amylose, a hydrocolloid, comprises largely unbranched α-(1→4)-linked glucan chains and does not appear to participate in the formation of the ordered part of starch matrix. Around 30% of barley starch is comprised of this polymer, and, within the starch granule, amylose molecules appear to be interspersed in a single-helical or random-coil form between amylopectin molecules. Evidence suggests that amylose synthesis is dependent on, and even controlled by, amylopectin synthesis.

The suitability of cereal starches for their intended uses is dependent on their amylose/amylopectin ratios. Historically, amylose has been determined by the measurement of its iodine-binding capacity (e.g., colorimetrically). Unfortunately, the test can be deceptive—amylopectin-iodine complexes also form and these may lead to overestimation of amylose. There are now methods by which amylopectin can be sequestered (for example, by binding it with the lectin concanavalin A), which renders it unavailable for reacting with iodine. Molecules of amylose consist of anywhere from 200 to 20,000 glucose units, depending upon starch source.