Enzymatic Approaches for Structuring Starch to Improve Functionality

Starch is one of the most abundant renewable biopolymers in nature and is the main constituent in the human diet and a raw material for the food industry. Native starches are limited in most industrial applications and often tailored by structural modification to enhance desirable attributes, minimize undesirable attributes, or create new attributes. Enzymatic approaches for structuring starch have become of interest to the food industry precisely because the reactions minimize the formation of undesirable by-products and coproducts and are therefore considered environmentally friendly methods for producing clean-label starches with better behavioral characteristics. Starches with improved functionalities for various applications are produced via enzyme hydrolysis and transfer reactions. Use of novel, multifunctional, starch-active enzymes to alter the structures of amylose and/or amylopectin molecules, and thus alter the starch's physiochemical attributes in a predictable and controllable manner, has been explored. This review provides state-of-the-art information on exploiting glycosyl transferases and glycosyl hydrolases for structuring starch to improve its functionalities. The characteristics of starch-active enzymes (including branching enzymes, amylomaltases, GH70 α-transglycosylases, amylosucrases, maltogenic amylases, cyclomaltodextrinases, neopullulanases, and maltooligosaccharide-forming amylases), structure-functionality-driven processing strategies, novel conversion products, and potential industrial applications are discussed.