Structural characterization and fluidness analysis of lactose/whey protein isolate composite hydrocolloids as printing materials for 3D printing.

[Display omitted] • Lactose/WPI composite hydrocolloids were considered as ink materials in 3D printing. • Lactose-derived co-solvation can help to avoid WPI aggregation and enhance fluidness. • Shearing and mechanical τ can be modelled by WLF with material-special constants. • Fluidness measures flow property and gives an "printable indicator" for hydrocolloids. In this study, the lactose/Whey Protein Isolate (WPI) composite hydrocolloids were prepared as an printing material for subsequent 3D printing. The results showed that the rheological, viscoelastic, thermal and mechanical properties of the studied hydrocolloids were composition dependent, which was directly linked to the printing fidelity of printed objects. The morphology of all printed objects showed a porous microstructure, and their porosity was changed by lactose addition. This outcome resulted from lactose-derived co-solvation discouraging WPI aggregation during the printing process, which was necessary for improving printing performance. Moreover, an innovative Fluidness concept (F), using material-specific WLF analysis of relaxation times, was introduced to quantify the fluidness of lactose/ WPI composite hydrocolloids at a certain decay of timescales (from 102 to 10-3 s). This F concept was superior for the description and control of printing fidelity, dimensional deviation, and textural properties of 3D -printed objects. Therefore, the F concept is a "printable indicator" for dairy by-products that may possess proper printability and provides an alternative approach to make attractive designs for 3D printing foods. [ABSTRACT FROM AUTHOR]