Fabrication of starch-based oleogels using capillary bridges: Potential for application as edible inks in 3D food printing

Food-grade oleogels may be used as edible inks in 3D food printing applications. However, there is currently a lack of simple and robust methods of fabricating oleogel-based edible inks with tunable printing properties. In this study, native starch-based oleogels were prepared from starch, oil, and water. Initially, powdered starch was dispersed into soybean oil and then water was added to promote starch aggregation through capillary attraction. The impact of adding xanthan gum to the water was also investigated, as it is known to greatly impact its rheology. The impact of starch, water, and xanthan gum content on the structure, rheology, and stability of the oleogels was then evaluated using magnetic resonance imaging, dynamic shear rheometry, and confocal scanning laser microscopy. The properties of the oleogels could be modulated by altering the starch and water content, as these parameters influenced the formation of a space-spanning particle network held together by capillary forces. Adding xanthan gum to the water had little impact on oleogel properties, which was attributed to the dominance of capillary forces in oleogel formation. The starch oleogels exhibited physicochemical characteristics that made them suitable as edible inks in 3D food printing applications, including high printing accuracy and the ability to maintain their shape after printing. Tribology analysis showed that the oleogels exhibited mixed lubrication behavior, with the lowest lubricity being observed at S = 0.2, φP = 0.38. In conclusion, this study shows that starch oleogels with controllable properties may be suitable as edible inks for food applications.