As we all know starch is lots of units of glucose bolted together. Yeast can’t eat starch because it’s so big. Yeast doesn’t have the necessary tools to unbolt the glucose. During malting and mashing, enzymes unbolt the glucose so that when the brewers add yeast it has something to eat.
This week’s flavour compound is made when the malt enzymes can’t finish the job and is known as dextrin(s). Dextrins are like starch, lots of glucose molecules bolted together, they are just much smaller. Dextrins make a beer feel full and sometimes sweet in the mouth. The more the brewer and maltster convert into sugar the thinner (lighter) and drier the resultant beer feels. Dextrins are not the only source of body in beer but are generally considered as the most significant.