Characterization of native starch granules from different botanical sources and the contribution of surface-associated lipids and proteins to the accuracy of 3D food printing

Abstract

3D printing of starch-based materials has become of great interest during the last few years. However, the characterization of the printing inks and the prediction of the printing accuracy is still challenging. Therefore, the surface chemistry and particle size distribution of starches from different organic sources (wheat, potato, rice) were characterized, and their influence on printing accuracy was investigated. Starch granules surface is covered with different lipids (e.g. phospholipids) and protein (e.g. puroinduline), which are known to influence the properties of starch and the interaction with other ingredients. These surface-associated lipids (SSAL) and proteins (SSAP) were removed individually from starch granules' surfaces to investigate the influence of particle-particle interplay on the printing behavior. Therefore, the amount of surface proteins was calculated by XPS analysis based on the nitrogen to carbon (N/C) ratio of each starch granules' surface. There was a linear correlation (r = −0.84) between the N/C ratio and the printing accuracy, measured by a geometrical deviation, indicating a dominating influence of the surface composition of the individual starch granules. The deviation from the geometrical template was higher for printed samples with smaller N/C ratio and therefore less protein on the starch granules’ surface. No influence of the particle size was found, as the samples from different starches containing the same amount of SSAPs had the same printing accuracy. These results reveal that the particle-particle and particle-polymer interactions mainly influence by the protein content on the starch granule surface seem to be decisive for the geometrical stability of 3D food printing. It is therefore recommended to use starches with a high amount of SSAPs for 3D printing applications.