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. Practical Application Vegetarian foods are widely consumed, especially in Asia. Some solid foods in the form of gel normally contained gelatin, which is from animal. Thus, a search for a meat-free ingredient is useful. The obtained cassava starch modified by amylomaltase produced from Corynebacterium glutamicum shown to have good thermo-reversibility and freeze–thaw stability properties, which can be applied to food products. This will benefit the industrial vegetarian food production to ensure the nonmeat ingredients in their product.