Effect of particle size on 3D printing performance of the food-ink system with cellular food materials

The effect of the particle sizes (307, 259, 172, and 50 μm) on rheological properties and printing performance for a food-ink dispersion system that 20% (w/w) of spinach powder was incorporated in 10% (w/w) xanthan gum mixture was investigated. Scanning electron microscopy images demonstrated that the larger particle size (307 μm and 259 μm) possess a skeletal-like and cellular structure, and are more porous than the smaller particle size (up to 172 μm). The increase of particle size significantly affected the composition and bulk density (ranged from 0.15 for 50 μm to 0.22 for 307 μm) of the spinach powder. Reduction in particle size resulted in the increase of water and oil holding capacity, but did not affect the water solubility index. Increasing particle size promoted a rise of the values of the storage modulus and loss modulus systematically. The shear modulus of spinach dispersion was ranged from 2.97 ± 1.26 kPa for finest size (50 μm) to 6.43 ± 1.41 kPa for a particle size of 307 μm and increased with increasing particle size. All dispersions were printed smoothly regardless of the particle size. The results obtained in this study suggest that increasing the particle size of the incorporated food powder can achieve efficient mechanical strength increase and a limit the incorporated powder content, simultaneously, due to its excessive increase. This may be useful in determining parameters which required to prepare the food-ink system such as the milling time and the maximum incorporation content of the food powder.