Model 200 f3 maia

The gelatinization properties of starch were estimated by differential scanning calorimetry (DSC, Model 200 F3 Maia, NETZSCH, Waldkraiburg, Germany) following the method of Lu et al. [26 (link)]. Each sample (5 mg, dry weight) was loaded into an aluminum pan (25/40 microliters, D = 5 mm), and distilled water was added to achieve a starch-water suspension containing 66.7% water. Samples were hermetically sealed and allowed to stand for 24 h at 4 °C before heating in the DSC. The DSC analyzer was calibrated using an empty aluminum pan as a reference. Sample pans were heated at a rate of 10 °C/min from 20 to 100 °C. Thermal transitions of starch were defined as onset temperature (T_o), peak gelatinization temperature (T_p), conclusion temperature (T_c), and gelatinization enthalpy (ΔH_gel). Samples were stored at 4 °C for 7 days after thermal analysis for retrogradation investigations. Retrogradation enthalpy (ΔH_ret) was automatically calculated, and retrogradation percentage (%R) was computed as %R = 100 × ΔH_ret/ΔH_gel.

The starch pasting properties were tested using a rapid viscosity analyzer (RVA) (Model 3D, Newport Scientific, Warriewood, Australia) according to the method of Lu and Lu [32 (link)]. Briefly, rice flour at a concentration of 12% (w/w) was mixed at a constant stir speed of 160 g using the standard profile. The temperature profile employed was as follows: the start temperature was 50 °C held for 1 min, followed by heating to 95 °C at 11.84 °C/min, held at 95 °C for 2.5 min, and then cooling at the same speed to 50 °C and held for 1 min.
The thermal properties were investigated by a differential scanning calorimetry (DSC) with a Model 200 F3 Maia (Netzsch, Selb, Germany). Using an empty aluminum pan as a reference, the ratio of the weight of starch to water was 1:3 for each sample, which was sealed in a hermetic aluminum pan and scanned from 30 to 95 °C at a heating rate of 10 °C/min after overnight equilibration at room temperature [33 (link)]. The thermal transitions of starch samples were defined as To (onset temperature), Tp (peak of gelatinization temperature), and Tc (conclusion temperature), and ΔH referred to the enthalpy of gelatinization.