Enzymatic conversion of α-1,4 to α-1,3 linkages by glyco transferase for tailoring cassava starch structure and digestibility

Cassava starch was enzymatically modified using Glyco Transferase “Amano” L (GLT), a 4-α-glucanotransferase capable of converting α-1,4 into α-1,3 glycosidic linkages. The effects of different enzyme concentrations on structural, physicochemical, rheological, and digestive properties were investigated. Increasing GLT dosage caused progressive surface erosion and decreased short- and long-range molecular order, while overall chemical composition remained unchanged. Relative crystallinity declined from 30.10% to 17.61%, accompanied by reductions in peak, final, and setback viscosities, indicating weakened granule integrity and lower retrogradation tendency. In vitro digestion showed that rapidly digestible starch decreased from 63.42% to 48.16%, while resistant starch (RS) increased from 7.42% to 18.33%. Notably, the modified starch exhibited higher RS content but lower viscosity, contrasting with the conventional correlation between high RS and high setback viscosity. This unique behavior arises from linkage rearrangement rather than recrystallization. GLT modification thus provides a green and controllable approach to produce low-glycemic, low-viscosity starch ingredients suitable for functional and texture-controlled foods.