Effect of κ-carrageenan on physicochemical and 3D printing properties of walnut protein-stabilized emulsion gel

Walnut protein (WP) -stabilized oil -in -water (O/W) emulsion gel can be used to produce food through 3D printing, but there was a problem of poor printing accuracy. We added kappa -carrageenan (KG) to enhance the shape retention of corresponding printed products. In this study, the effect of KG on various physicochemical properties of the WP -stabilized O/W emulsion gel was investigated. The rheology results showed that adding KG significantly enhanced the mechanical strength and the viscosity of the produced WP -KG emulsion gel. The Lissajous curves indicated that the response of all samples under 10% low strain was mainly elastic, and the gels with 0.2, 0.3 and 0.4 (w/w) KG had great shear recovery performance against deformation. The increased KG content in the gel reduced the number of pores, promoted emulsions droplet aggregation, reduced crystallinity, and decreased the water -binding ability of the gel. Adding KG to the gel significantly increased its hardness, resilience, and gumminess while reducing its springiness. Various emulsion gels with different KG contents were further used as the bioink for 3D printing. The result suggested that KG improved the printing accuracy and selfsupporting ability of 3D -printed products. However, excessive KG ( > 0.4%, w/w) caused uneven extruded filaments, reduced the adherence between printed layers and decreased printing accuracy. Among various WP -KG emulsion gels, WP-KG0.3 was most appropriate for the 3D printing application.