Rheology and 3D printing characteristics of heat-inducible pea protein-carrageenan-glycyrrhizic acid emulsions as edible inks

Protein-based emulsion gels, especially those induced by heat, have been widely used in food 3D printing. However, the rheology and texture of protein-based gels are important factors restricting 3D printing. In this study, glycyrrhizic acid (GA) was used to improve the rheology properties of pea protein (PP)-Kappa carrageenan (κCA) composite emulsion inks, and the suitability of these inks for extrusion 3D food printing was investigated. The results showed that all emulsion inks have shear thinning behavior and could be smoothly extruded during 3D printing. Herschel-Bulkley model fitting results proved that with the increase of PP concentration (from 5% to 10%), the yield stress (σ0) increased from 15.4 to 28.19 Pa, and the consistency coefficient (k) increased from 1.09 to 2.66 Pa.sn. The objects printed with 10% PP-GA0.3 inks showed excellent self-supporting capability, a smooth surface texture, and high printing accuracy. Emulsion inks had good temperature stability and could form emulsion gels following heat induction. The results of small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) tests confirmed that the addition of GA improved the strength of the gels. This research provides valuable insights for the advancement of food 3D printing inks.