Personalized, digitally designed 3D-Printed protein substitutes: Advancing medical food for PKU patients

Phenylketonuria (PKU) is a rare inherited metabolic disorder requiring lifelong restriction of phenylalanine (Phe) intake. This study aimed to develop and characterize 3D-printed protein substitute medical foods based on glycomacropeptide (GMP), a natural Phe-free peptide derived from cheese whey, tailored for PKU patients. Cocoa butter was used to facilitate extrusion performance. Three inks containing cocoa butter, tagatose and pineapple powder, with varying concentrations of GMP and selected amino acids, were developed to yield protein-equivalent contents ranging from 24 % to 31 % (w/w) and Phe contents respectively between 1.76 and 1.79 mg per gram of protein equivalent; these formulations were evaluated for printability, thermal and rheological properties, mechanical strength, wetting behavior, color and sensory attributes. All food inks achieved high printing accuracy and stable structures. Tempering imparted structural integrity and favorable physicochemical properties to the inks; this stability was maintained post-3D-printing, as evidenced by wetting behavior analysis. Thermal and rheological analyses demonstrated that higher GMP concentrations enhanced the viscosity and thermal stability of the inks, while mechanical testing of the 3D-printed structures indicated improved matrix rigidity with increased GMP content. Sensory evaluation of the obtained snacks using Temporal Dominance of Sensations (TDS) showed distinct oral perception profiles across formulations, with higher GMP content linked to increased adhesiveness and prolonged flavor perception. However, inks with higher tagatose levels exhibited more prominent sweetness. The findings suggest that 3D printing may be a feasible approach for producing customized, palatable medical foods for PKU patients, with GMP serving as a key functional protein.