Extrusion-based 3D printing of pickering high internal phase emulsions stabilized by flaxseed protein-sodium alginate complexes for encapsulating curcumin

In the present work, sodium alginate-based complex (flaxseed protein-sodium alginate) electrostatic complexes (FP-AG) were fabricated, acting as an effective emulsifier for the first time to stabilize Pickering high internal phase emulsions (HIPE). Interactions between FP and AG were evaluated by isothermal titration calorimeter and quartz crystal microbalance with dissipation monitoring. These results suggested that electrostatic interactions played a dominant role in FP-AG complexation, and stronger interactions between FP and AG occurred under acidic conditions, forming more viscoelastic layers. FP-AG complexes at pH 4.0 (FP-AG4) exhibited appropriate wettability (87.9°). HIPEs were prepared using FP-AG4 (HIPE-C), contrasted with FP at pH 8.0 (HIPE-P) as a control. Rheological results suggested that HIPE-C exhibited shear-thinning behavior (extrusion), high thixotropy (recovery), and high viscoelasticity (self-supporting), which possessed a great potential for 3D printing. Moreover, 3D printing and the stability of curcumin of HIPE were explored simultaneously for the first time. These results showed that HIPE-C exhibited outstanding printability and printing models presented smooth surfaces, regular shapes, and distinct resolution. HIPE-C showed a better protection for curcumin against ultraviolet and thermal treatments than HIPE-P. FP-AG complexes could be used as an effective HIPE stabilizer and novel edible ink with good 3D printability in food industry.