Exploring the role of insoluble dietary fibre from date fruit (Phoenix dactylifera L.) in stabilizing the 3D cookie printing structure

Insoluble date fruit fibre (DF) from different date fruit cultivars (Barhi, Shishi and Neghal) was used respectively as a structural reinforcing agent in three-dimensional (3D) food printed cookies. The effect on the printed 3D cookie ink and baked cookies from using DF together with mixed variety industrial pomace (IP) at various concentrations (0, 3, 6 and 9% w/w) was analysed based on the rheology, dimensional stability and microstructure. Barhi and IP DFs were rich in lignin, with low amounts of co-existing soluble fibre, whereas Neghal and Shishi DFs showed the opposite composition. The ink rheological properties and baked cookie texture were affected by the DF cultivar and concentration. Inks formulated with Neghal and Shishi DFs exhibited higher G' values compared to Barhi and IP DF inks, consistent with the dough tan δ values at corresponding concentrations. High DF amounts resulted in ink with darker notes, reflecting the compositional and pigment effects. Ink hardness increased with increasing DF concentration, while cohesiveness and springiness decreased, due to denser network. DF baked-printed cookies were hard and fractured easily, particularly Barhi DF cookies at a high DF level. Neghal printed cookies containing 6% DF were softer, retained the shape with high fidelity (100%), suggesting that 6% DF is the most favourable level to prevent cookie spreading during baking. Cookie microstructure analysis showed that 9% DF resulted in printing discontinuity with layer gaps and separation, due to poor cohesiveness and brittle structure. These findings suggest that DF addition shows promising results, offering a sustainable approach to valorise food waste as well as tailoring textural cookie properties.