Design and evaluation of a coaxial extrusion system for alginate-based 3d food printing

Introduction: Coaxial extrusion 3D printing offers a novel technique over conventional single-nozzle printing by utilizing a dual-channel nozzle to simultaneously deposit two materials concentrically. This approach unlocks new possibilities for food texture and nutritional value, providing structural stability and a specific sensory experience. This system enables the encapsulation of sensitive ingredients within a protective external matrix. The present work focuses on the design, formulation, and evaluation of a food ink for coaxial 3D printing, utilizing an ionic encapsulation system composed of a sodium alginate external matrix and a zinc-fortified whipped cheese internal core. Whipped cheese proteins (such as casein) facilitate the absorption of this mineral in the body, as the amino acids present in the dairy product act as natural ligands that improve zinc bioavailability.

Methods: Printing conditions were studied, and alginate solutions (2.0%, 2.5%, and 3.0% w/w) were evaluated to determine the optimal concentration for printability by analyzing their viscoelastic behavior and textural properties. The printability index (Pr) and syneresis behavior were assessed over time. Finally, ICP-OES was used to precisely quantify the presence and retention of calcium and zinc within the optimized matrix.

Results: The high content of calcium cations in the cheese enabled ionic gelation upon contact with the alginate, enhancing the structure without altering rheological properties. Experimental results identified the 2.5% (w/w) alginate formulation as the most suitable concentration, providing the best functional balance, greater dimensional stability, and maximum viscoelastic recovery. Finally, ICP-OES spectrometry precisely quantified the presence and retention of calcium and zinc within this matrix, validating its potential as a functional food.

Conclusions: Coaxial extrusion 3D printing successfully yielded a core-shell structure with the geometric fidelity required to efficiently retain micronutrients, maintaining the morphological integrity of the sample against syneresis phenomena.