Effect of Hydrocolloids on Rheological Properties and Printability of Vegetable Inks for 3D Food Printing

Abstract: In food ink systems in which the particles are dispersed in a hydrocolloid matrix, the source of the particles and the particle content are the main factors affecting the printability and rheological properties of the system. In this study, different contents (10% and 30% w/w) of vegetable (broccoli, spinach, or carrot) powders were added to hydrocolloid matrices with different hydration properties, and their influence on the printability and rheological properties was investigated. At low powder contents (10%), slight differences in the printability and rheological values were observed between the different vegetable sources in all hydrocolloids. When the powder content was increased to 30%, the hydrocolloid with the lowest water hydration capacity, hydroxypropyl methylcellulose, showed the greatest differences in rheology and printability when different vegetable sources were used. Xanthan gum, with its higher water hydration capacity, inhibited the swelling of the particles, thus minimizing the increase in the rheological values at high volume fractions of powder and reducing the differences in printability between different vegetable sources. Confocal laser scanning microscopy analysis of the vegetable inks showed that xanthan gum inhibited swelling of the particles regardless of the vegetable powder source. The mixtures using xanthan gum could be smoothly extruded from the nozzle due to their low extruded hardness (2.96 ± 0.23 to 3.46 ± 0.16 kg), and the resulting objects showed high resolution without collapse over time. Practical Application: The powder-based texturization technology introduced in this study provides a standardized method of preparing food ink that can be universally applied to all food materials that can be powdered. In addition, the present invention can be applied to a 3D printing technique in which a powder and a hydrocolloid matrix are independently stored and mixed immediately before printing. This technique can minimize the inherent rheological differences between formulations with different food sources and compositions.