An engineering approach to the 3D printing of K-Carrageenan/konjac glucomannan hydrogels

Abstract

Aqueous solutions of Konjac glucomannan (KGM)/κ-Carrageenan (κ-C) of different ratios (1:2, 1:5, 1:8 and 1:10) and a fixed κ-C content of 1.5%, were proposed as a new 3D food printing ink. Their thermo-responsive behaviour was evaluated by temperature ramp rheological tests. This characterisation allowed for the evaluation of the synergistic effect between KGM and κ-C and gave indications useful to the printing performance. Both elastic (G′) and loss (G″) moduli were found to increase by increasing the KGM concentration. Samples were printed by controlling the thermally reversible sol/gel transition occurring during the process. Direct pressure and flow rate measurements in the 3D printer were used to obtain the viscosity versus shear rate curves under processing conditions, useful to validate a scaling law relating the printing filament diameter to the relevant process and material properties (inks viscosity and printing pressure). The 3D printing performance of inks was evaluated by means of a novel, integrated score system. The results obtained indicate that aqueous mixtures of KGM/κ-C can be successfully employed as a base for 3D printing food hydrogels. The use of the score system above outlined proved to be an easy yet efficient tool for the optimisation of the gel composition.