Enabling direct ink write edible 3D printing of food purees with cellulose nanocrystals

Additive manufacturing using edible feedstock - known as "edible three-dimensional (3D) printing" - offers a unique method of producing visually appealing meals with customizable nutrition profiles. Direct ink write (DIW) 3D printing is a popular choice for edible 3D printing due to its low cost and open framework for broad material choices. However, the breadth of food suitable for DIW 3D printing is hindered due to the unsuitably low viscosity of many potential edible feedstocks such as food purees. In this paper, we present cellulose nanocrystals (CNCs) as a safe and renewable rheological modifier capable of enabling DIW 3D printing of a variety of foodstuffs, specifically spinach puree, tomato puree, and applesauce, and using freeze-dry to obtain final solid structures. We first analyzed the rheological characterization of foodstuffs combined with varying volume fractions of CNCs to produce shear-thinning, printable inks. The print quality of different inks was then analyzed via image processing techniques. Finally, we demonstrated the capability of CNC-laden inks by printing a variety of structures, including multi-material structures with integrated packaging. This study found that CNCs are an effective rheological additive which promoted shear-thinning, viscous behavior in the studied edible feedstocks necessary for DIW 3D printing of self-supporting edible structures.