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Amylose is a starch molecule that consists of a straight chain of linked glucose molecules (1-4 carbon link). It is found in brewing grains and is converted to simpler, fermentable sugars during the mashing process.
These complex sugars can not be completely broken down into simple by amylolytic enzymes. The larger chain fragments that remain are amylodextrins. These are neither soluble nor fermentable.
The starch content of barley is approximately 25 percent amylose.