Synthesis and physicochemical properties of carboxymethyl chestnut starch

Abstract

Carboxymethyl chestnut starch (CMCS) was synthesized by the reaction of chestnut starch and monosodium chloroacetate in an alkali environment. The hydroxyl groups of starch were etherized through carboxymethyl groups, and the crystallinity of starch was reduced after carboxymethylation. As degree of substitution (DS) increased from 0.22 to 0.63, the degree of amyloglucosidase hydrolysis decreased from 37.0 to 1.6%, which was markedly lower than that of native chestnut starch (NCS) (83.2%). The differential scanning calorimetry results revealed the absence of a transition peak in all CMCS samples. CMCS paste showed significant higher light transmittance and freeze-thaw stability than those of NCS, and had no water release during storage at room temperature. CMCS with middle DS showed higher viscosity than NCS at high shear rate. The results demonstrated that CMCS can be applied in the industrial processing of paste foods and frozen food as a thickening agent. Practical applications Carboxymethylated starch can be used as an alternative thickener in a wide range of industrial applications. However, there is little information on the synthesis and physicochemical properties of carboxymethylated chestnut starch till now. In the present study, the carboxymethylated chestnut starch was synthesized by the optimization of process, and the microstructure, light transmittance, and freeze-thaw stability of starch were studied. We believe that starch industry can utilize the results of this study in the synthesis and application of this modified starch.