Hydroxypropylated/oxidized starch-based regulation of the potato-barley system for extrusion-based 3D food printing

In this study, composite gels based on potato puree and barley seedling powder were formulated with hydroxypropylated starch (HPS) and oxidized starch (OS) as structural modifiers for extrusion-based 3D food printing. The effects of modified starch type and concentration (8-16%, w/w) on the rheological properties, microstructure, water distribution, and printability of the gels were systematically investigated. The results suggested that all samples exhibited shear-thinning behavior, which was favorable for extrusion-based printing. Increasing modified starch concentration significantly increased the storage modulus (G'), loss modulus (G''), viscosity, and hardness of the gels, indicating the formation of stronger gel networks. Compared with HPS-PB gels, OS-PB gels showed higher moduli and a denser microstructure, reflecting stronger intermolecular interactions. The Fourier-transform infrared spectroscopy (FT-IR) results indicated that HPS and OS weakened and enhanced the hydrogen bonds within the system, respectively. Low-field nuclear magnetic resonance (LF-NMR) analysis further revealed significant differences in water mobility between the two modified starch systems. Among the two types of starch gels, HPS-16% and OS-8% exhibited the most favorable balance between extrusion stability and shape retention. These findings provide useful insights for designing modified starch-based gel systems for extrusion-based 3D food printing.