Molecular and Rheological Insights into Apple Pectin─Poly(ethylene glycol) Gelation in Aqueous Media

The gelation behavior of pectin from apple (AP) and poly(ethylene glycol) (PEG) systems in water offers a promising alternative to conventional high-solids and low-pH pectin gels, which often suffer from syneresis and strict processing conditions. However, the structural complexity arising from polymer-polymer and polymer-solvent interactions in these systems remains poorly understood, necessitating a deeper characterization of their physicochemical behavior. This knowledge gap is particularly relevant given the sensitivity of gel formation to both composition and processing parameters. Herein, gelation in ternary AP/PEG/water systems is examined across a range of compositions (AP (4-10 wt %) and PEG (40-80 wt %)), using rheology and ¹H NMR spectroscopy to probe the network formation, mechanical properties, and water dynamics. This work demonstrates that PEG acts as a water-activity modulator promoting junction zone formation, and provides a cross-scale mechanistic picture linking molecular water dynamics to macroscopic AP-PEG gel mechanics.