Preparation and characterization of carboxymethyl starch from cadmium-contaminated rice

Cadmium-contaminated rice has been a serious food safety issue in China. In this research, carboxymethyl rice starch (CMS) from cadmium-contaminated rice and native rice was prepared to remove the cadmium in rice. The preparation of native rice starch (NRS) and starch from cadmium-contaminated rice (Cd-CRS) was similar, and carboxymethyl starch was prepared following the same steps. A single factor experiment was performed to obtain the carboxymethyl starch prepared under the optimal conditions. Cadmium content was reduced from 0.38 mg/kg to 0.04 mg/kg after alkalization. The physical properties, including particle size, degree of crystallinity, water absorption and freeze-thaw stability, of NRS and Cd-CRS and their carboxymethyl starches were studied. The results showed that the cadmium was significantly removed after extracting starch from cadmium-contaminated rice by alkalization and carboxymethylation. Then, starch samples and carboxymethyl starch samples were characterized. All results showed no obvious difference between Cd-CMS and NCMS, indicating that carboxymethyl starch from cadmium-contaminated rice could be widely used in both food and nonfood industries.