Physicochemical Properties and Functionality of Highly Carboxymethylated Starch

Highly carboxymethylated potato starches (HCMS) with various degrees of substitution ranging 0.48‐0.60 were produced and their physicochemical and functional properties were examined. The degree of substitution could be increased by prior treatment of starch with acid, although the longer the treatment the percentage of low molecular weight starches increased slightly. HCMS showed a pseudoplastic flow having the power law index less than 1.0. HCMS swelled readily in cold water (15°C), formed a clear solution, and were resistant to retrogradation. The viscosity of HCMS prepared without or with 15min acid treatment was similar or higher than that of native starch at the beginning of amylography, however, it decreased gradually from the rest of the stage. HCMS prepared with longer acid treatments exhibited extremely low viscosity throughout the test period. The digestibility of HCMS by α‐amylase decreased greatly in proportional to the degree of substitution. Scanning electron microscopic observation revealed fine fissures and grooves on the surface of HCMS granules, suggesting part of amylose has been leached by the acid treatment.