Application of Pickering emulsions in 3D printing of personalized nutrition. Part I: Development of reduced-fat printable casein-based ink

The application of surface-active biopolymers supports opportunities and novel prospects to generate a well-defined printable ink for 3D printing. In this regard, an ideal ink must show pseudoplastic, viscoelastic, and thixotropic characters with a recoverable structure so as to be effectively printed with desired printability. Here, microcrystalline cellulose was hydrophobically modified through a facile and sustainable acetylation method. Then, the functionalized microcrystalline cellulose was incorporated into a casein-based emulsion for being replaced to its partial fat (15–60% fat reduced). The significant effect of micro-biosurfactant on the rheological properties of casein-based emulsion enhanced its shear-thinning, thixotropic, and viscoelastic features. The use of higher ratios of micro-biosurfactant produced an emulsion with greater elastic modulus, smaller droplet sizes, improved stability to the permanent deformation, and increased the nonlinear behavior of the system under large amplitude oscillatory shear stress. The results of the temperature ramp also confirmed the thermo-reversible property of the ink, which was noticeably dependent on the ratios of micro-biosurfactant. The results of this study provided fundamental knowledge about emulsion stability in terms of the contribution of the hydrophobically modified microcrystalline cellulose to interface stability and in promoting resistance to shear stress and deformation. These results allow one to gain a profound understanding of the printability and extrudability of these classes of biomaterials.