Salt-Induced Rheological Modulation of Glucose Syrup: A Novel Approach for Humidity-Controlled Food Packaging

Glucose syrup (GS) is a viscous aqueous solution widely used in food products. Since the addition of salt alters the rheological properties of food systems by promoting inter- and intramolecular interactions, the purpose of our study was to investigate the rheological properties of GS and GS–salt mixtures at various ratios. According to the results, the apparent viscosity of GS increased from 214 to 379, 590, and 668 Pa·s upon salt addition at the ratios of 8:1, 4:1, and 2:1, respectively (shear rate: 44.1 s⁻¹). GS exhibited a solid-like behavior (G^′ > G^″), which shifted to a concentrated solution behavior at the ratios of 8:1 and 4:1 and to a more elastic behavior at the 2:1 ratio upon salt addition. Time sweep tests and relative humidity measurements revealed that salt addition slowed desorption of water molecules from GS surface by forming dipole bonds with water molecules, preventing barrier layer formation. Consequently, the GS–NaCl mixtures exhibited sustained water release and effectively increased the relative humidity of the container, highlighting their potential as viscous humidity modifiers. We propose a novel active packaging system that incorporates the GS–NaCl mixture into a double-walled container to gradually increase headspace relative humidity. This approach can minimize moisture loss and prevent food dehydration without direct contact between the GS–NaCl mixture and the product.