Properties of Cassava Starch Modified by Amylomaltase from Corynebacterium glutamicum

Amylomaltase (α-1,4-glucanotransferase, AM; EC 2.4.1.25) from Corynebacterium glutamicum expressed in Escherichia coli was used to prepare the enzyme-modified cassava starch for food application. About 5% to 15% (w/v) of cassava starch slurries were incubated with 1, 3, or 5 units of amylomaltase/g starch. Apparent amylose, amylopectin chain length distribution, thermal properties, freeze-thaw stability, thermo-reversibility, and gel strength of the obtained modified starches were measured. The apparent amylose content and retrogradation enthalpy were lower, whereas the retrogradation temperatures, freeze-thaw stability, and thermo-reversibility were higher than those of the native cassava starch. However, when amylomaltase content was increased to 20 units of amylomaltase/g starch and for 24 h, the modified starch showed an improvement in the thermo-reversibility property. When used in panna cotta, the gel strength of the sample using the 20 units/24 h modified cassava starch was similar to that of using gelatin.