Appears in
Oxford Companion to Sugar and Sweets

By Darra Goldstein

Published 2015

  • About

starch is a digestible carbohydrate made by chaining together hundreds or thousands of glucose molecules. Plants produce starches from carbon dioxide and water through photosynthesis. The linkages between glucose units are readily broken, enabling plants, as well as organisms that consume plant material, to rapidly reclaim the individual simple sugar units to use as an energy source. In the kitchen, starches are used to thicken sweet and savory sauces, and to help puddings and fillings set.

Starch molecules can be classified by their three-dimensional molecular structure. Amylopectins are highly branched and fold into sheet-like structures, while amyloses are smaller, helically shaped molecules with minimal branching. Roughly three-quarters of the starches in plants are amylopectins. The spiral units of amyloses pack tightly together, making them substantially less soluble than amylopectins. Starch molecules pack into larger granules, ranging in size from 1 micron to over 0.1 millimeters in diameter.