Long-Term Retrogradation Properties and In Vitro Digestibility of Waxy Rice Starch Modified with Pectin

In recent years, the blending of hydrocolloids and natural starch to improve the properties of natural starch has become a research hotspot. In this study, the effects of pectin (PEC) on the retrogradation properties and in vitro digestibility of waxy rice starch (WRS) were investigated. The results showed that PEC could significantly (p < 0.05) reduce the retrogradation enthalpy and reduce the hardness of WRS gel. X-ray diffraction results indicated that PEC could reduce the relative crystallinity of the composite system, and the higher the PEC content, the lower the relative crystallinity. When the PEC content was 10%, the relative crystallinity of the composite system was only 10.6% after 21 d of cold storage. Fourier transform infrared spectroscopy results proved that the interaction between PEC and WRS was mainly a hydrogen bond interaction. Furthermore, after 21 d of cold storage, the T₂₃ free water signal appeared in the natural WRS paste, while only a small free water signal appeared in the compound system with 2% PEC addition. Moreover, addition of PEC could reduce the starch digestion rate and digestibility. When the content of PEC increased from 0% to 10%, the digestibility decreased from 82.31% to 71.84%. This study provides a theoretical basis for the further application of hydrocolloids in starch-based foods.