4D printing of a citrus pectin/β-CD Pickering emulsion: A study on temperature induced color transformation

The 4D printing of a Pickering emulsion stabilized by citrus pectin/β-Cyclodextrin (β-CD) complexes was realized utilizing pH-sensitive curcumin. The fabrication, microstructure, and mechanical properties of the Pickering emulsion were investigated with laser confocal microscopy observations, rheological measurements and TPA. Results indicated that the emulsion prepared with an oil phase mass fraction (φ) of 65 %, composition ratio (Rβ/C) of 2:2, and citrus pectin/β-CD concentration (W) of 2 % exhibited smaller droplet size, strong gel network, and best printing performance. In addition, pH-sensitive curcumin was added to the emulsion to evaluate its 4D printing capabilities. The decomposition of HCO3- into CO32- resulted in the increase of pH after heating, induced the printed samples to change color from yellowish to red and the chroma of the samples changed accordingly: L*and b* value decreased while a* value increased. These findings offer greater flexibility to produce novel food formats and designs.