Role of Hydrophilic Colloids in 3D Printing of High-Moisture and Natural Glutinous Rice Flour Gels: Mechanisms of Retrogradation Inhibition and Stability Enhancement

Abstract

Glutinous rice flour paste, ideal for 3D printing due to its strong adhesive and mechanical properties, is limited by its tendency to retrograde. This study demonstrates hydrophilic colloids (guar gum, xanthan gum, and sodium alginate) can effectively mitigate this issue, especially over a 48-h storage period for high-moisture glutinous rice gels. The rate constant in retrogradation kinetics decreased from 0.044 to 0.013, indicating hydrophilic colloids effectively inhibited retrogradation. Differential scanning calorimetry (DSC) revealed that sodium alginate lowered retrogradation enthalpy (∆H) from 1.53 to 0.68 J/g (gel-free control group). Power-law modeling of dynamic frequency scans demonstrated higher gel strength (S′ and S″) for sodium alginate-based inks (1261.42 and 346.88 Pa) indicating better stability. Fourier transform infrared spectroscopy (FTIR) confirmed enhanced intermolecular hydrogen bonding, and sodium alginate-based ink showed a 7.1% reduction in short-range ordering (R_1047/1022) after 48 h. Low-field nuclear magnetic resonance (LF-NMR) also showed reduced transverse relaxation times (T₂) and water migration. The utilization of scanning electron microscopy (SEM) revealed the capacity of hydrophilic colloids to hold water was instrumental in the preservation of the gel structure. Overall, incorporating hydrophilic gels, particularly sodium alginate, prevents retrogradation and enhances the stability and longevity of 3D-printed food products.