Effect of papain on the gelling properties and 3D printability of thermally induced egg yolk gel

Food 3D printing technology has emerged as a prominent area of investigation in food processing due to its capacity for personalized manufacturing and precise nutritional regulation. Heat-induced egg yolk gel serves as a rich source of high-quality proteins and lipids, but its high hardness and low fluidity in thermogenic gels restrict its application in 3D printing. In this study, papain was employed to enzymatically hydrolyze egg yolk proteins, systematically examining its effects on the gel's physicochemical properties and 3D printability. Experimental findings demonstrated that enzymatic degradation significantly reduced the particle size and ζ-potential of the egg yolk suspension, disrupted the protein network structure, and decreased the storage modulus and apparent viscosity of the gels. The proportion of free water and network porosity in yolk gels increased with increasing papain concentration. Optimal results were observed at an enzyme concentration of 0.01–0.02 g/25 g, where the gel exhibited suitable viscoelasticity and self-supporting capability, enabling the successful printing of a structurally intact three-dimensional model. This research establishes a theoretical foundation for the development of enzymatically modified egg yolk-based 3D printing materials, thereby advancing the utilization of natural protein resources in smart food manufacturing.