Rheological behaviour, structural recovery and printability of customized chocolate inks for extrusion 3D printing

Background Chocolate ink for extrusion-based 3D food printing requires an optimal balance of rheological behaviour, structural recovery, and textural properties to ensure smooth extrusion, shape retention, and dimensional stability after deposition. This study investigates the influence of the cocoa solids-to-fat ratio on the rheological behaviour, structural recovery, and printability of custom-developed chocolate inks. Methodology Five formulations were prepared by varying cocoa solids (20–28%), cocoa butter (30–34%), and sugar (23.4–35.4%), while keeping the levels of milk powder, palm oil, lecithin, polyglycerol polyricinoleate, and vanilla extract constant. The inks were characterised using steady-state and oscillatory rheological measurements, including flow behaviour, viscoelastic properties, and creep-recovery tests, together with proximate and textural analysis for printability assessment. Results All formulations exhibited shear-thinning behaviour and viscoelastic solid characteristics suitable for extrusion-based 3D printing. The cocoa solids–fat ratio significantly influenced the rheological, textural, and printing properties of the chocolate inks. Formulation containing 22% cocoa powder and 31% cocoa butter achieved the optimal balance of extrusion flowability, structural recovery, texture, and printability, resulting in excellent shape retention. Variations in the cocoa solids–fat ratio also modified the proximate composition, particularly fat and total solids contents, thereby influencing the overall printing performance. Conclusion The cocoa solids–fat ratio is a critical formulation parameter governing the rheological, structural recovery, textural, and printing characteristics of chocolate inks. Optimising this ratio enables the development of chocolate inks with enhanced extrusion performance and dimensional stability, providing practical guidance for designing formulations for extrusion-based 3D food printing applications.