Preparation and physicochemical properties of carboxymethyl Fritillaria ussuriensis Maxim. starches

Starch isolated from an under-utilized Liliaceae plant (Fritillaria ussuriensis Maxim.) was carboxymethylated. Influences of reaction parameters were investigated on the degree of substitution (DS). The optimal molar ratio of NaOH/AGU and MCA/AGU is 2.43 and 1.03, respectively. The highest values of the DS obtained when the carboxymethylation was performed at 60 °C for 2.5 h. Scanning electron microscopy (SEM) showed that after carboxymethylation, the granular appearance of the native starch was distorted and many alveolate holes were seen. The new bands at 1608 cm−1 and 1426 cm−1 in Fourier transform infrared (FT-IR) indicated that the starch granules were substituted. Wide-angle X-ray diffractometry revealed that crystallinity was reduced significantly after carboxymethylation. Differential scanning calorimetry (DSC) suggests loss of crystallinity after carboxymethylation. The thermal behavior of the starches was investigated using thermogravimetric analysis (TGA). The results revealed that the decomposition temperature of the starch decreased from 316 °C to 252 °C and at a low decomposition speed.