Abstract
This study evaluated thiolated xanthan gum (XG-SH) as a reactive polysaccharide stabilizer for zein nanoparticle (ZNP)-based Pickering emulsions intended for bioactive delivery and extrusion-based 3D printing. Xanthan gum was selected as the modification platform because of its high aqueous solubility, stability over a broad pH and temperature range, and intrinsic shear-thinning behavior, all of which are advantageous for emulsion structuring and extrusion-based 3D printing. Unlike native Xanthan, thiolation introduces sulfhydryl groups that may promote disulfide-mediated interfacial cohesion and redox-active behavior. XG-SH was successfully synthesized using phosphorus pentasulfide, and showed a thiol content of 357.31 ± 39.01 µmol g⁻¹, as confirmed by Ellman’s assay, FTIR, and ¹H NMR. Thiolation reduced the magnitude of ζ-potential from −57.6 ± 2.3 mV for XG to −27.1 ± 1.7 mV for XG-SH. Compared with ZNP:XG, ZNP:XG-SH emulsions showed smaller droplets (4.93 ± 0.16 vs 9.76 ± 0.35 µm) and lower destabilization after 21 days (TSI = 5.12 ± 0.26 vs 10.02 ± 0.49). XG-SH also increased elasticity (G′ ≈ 1.3 × 10² vs 6.8 × 10¹ Pa), hardness (242.35 ± 5.98 vs 98.97 ± 2.36 g), and adhesiveness (310.21 ± 6.28 vs 151.17 ± 3.00 g ·s), indicating network reinforcement. After loading with Rubus idaeus leaf extract, XG-SH emulsions showed shorter induction time than ZNP:XG (328.30 ± 2.25 vs 404.30 ± 3.61 h), but higher antioxidant efficiency (129.58 ± 3.01 vs 103.10 ± 2.46). During 3D printing, XG-SH improved 48 h dimensional retention. Overall, XG-SH enhanced stability, rheomechanical properties, antioxidant response, and post-print structural fidelity.