Engineering Bigels for 3D Food Printing: Formulation Strategies, Printability, and Emerging Applications

Abstract Bigel-based 3D printing is emerging as a transformative strategy in food science. Their tunable rheological properties, capacity for high shape fidelity printing, and stability make bigels a promising class of food bio-inks for many applications. Despite rapid growth, systematic evaluation of the formulation strategies, printability metrics, and application-specific performances remains limited. This review systematically analyses peer-reviewed experimental studies that focus exclusively on edible bigels fabricated through 3D printing. A bibliometric survey highlights the rapid expansion of this field, which is dominated by contributions from China and supported by interdisciplinary inputs from food science, chemistry, and engineering. The literature is organised around formulation levers, including gelator selection, oleogel-to-hydrogel ratio, homogenisation techniques, and functional additives. These parameters are evaluated within a rheology-to-printability framework, with an emphasis on yield stress, shear thinning, and thixotropic recovery as determinants of printability. Application-specific performances are also summarised for fat analogues, dysphagia-oriented structures, bioactive carriers, and intelligent packaging. The review highlights recent advances in modifying bigel structures for 3D printing and points out several gaps, such as inconsistent reporting of formulations, limited knowledge on underlying mechanisms, and the lack of predictive models that connect rheology with printing results. The key research priorities involve creating mechanistic and predictive rheological models to support rational formulation design and standardising formulation and printability metrics for better cross-study comparisons. This review outlines a roadmap to promote bigel 3D printing as an innovative platform for custom, sustainable, and health-oriented food design.