Characteristics and properties of hydroxypropylated rice starch based biodegradable films

Abstract

The characteristics and properties of native rice starch (NRS) and hydroxypropylated rice starch (HPRS) in relation to HPRS films with 6–12% propylene oxide were investigated. The molar substitution of the resulting HPRS was in the range of 0.022–0.033. The results showed that gelatinization properties (To, Tp and Tc) and enthalpy (ΔH) of HPRS were lower than those of NRS, and these decreased with an increase in the propylene oxide. The pasting properties of the starch were determined by using a Rapid Visco Analyzer (RVA). The pasting temperature and peak viscosity was lower in the HPRS while the breakdown and setback viscosity was higher than in the NRS. In addition, the gel strength and paste clarity of HPRS demonstrated softer and clearer qualities than the NRS. The NRS and HPRS contained various concentrations of propylene oxide which were used for film preparation. The results showed that the elongation at break, water vapor permeability, film solubility and transparency of the HPRS films were higher than those of NRS film and increased with an increase in propylene oxide. In contrast, the tensile strength and yellowness (b*) of the HPRS films were lower than the NRS film and decreased with an increase in propylene oxide. The ether group band of the hydroxypropyl group in the FTIR spectrum was shifted from 990 cm−1 to 1015 cm−1 showing that the film was modified by propylene oxide. Moreover, the XRD analysis of the HPRS films showed a decrease crystallinity when the propylene oxide increased.