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Background: Maltose is an essential derivative of starch. To understand the processability and stability of maltose-containing foods, material characterization of the phase and state transition from its amorphous state is required. Although the crystallization of amorphous maltose is well understood, few studies have reported the relationship between the crystallization and the glass transition temperature (T g )-related molecular mobility. In this study, water sorption, crystallization, T g -related α-relaxation, and the corresponding time factor for amorphous maltose and maltose / whey protein isolate (WPI) mixtures are measured at various water activity (a w ) levels and 25 °C., Results: The water-additive principle for maltose / WPI mixtures was observed at a w  ≤ 0.440 at the molecular level, whereas the crystallization of amorphous maltose occurred at high a w values (≥0.534). The crystal formation and crystallization kinetics of amorphous maltose were affected by water and WPI at a w  ≥ 0.534 and 25 °C, as determined by X-ray diffraction. The relationship between T g and the water content was fitted by the Gordon-Taylor model, and its constant showed a compositional dependence for the maltose / WPI mixtures. The α-relaxation temperature of the amorphous samples decreased due to water plasticization, but increased with an increase in the WPI quantity. The Strength (S) value for amorphous maltose, which was a quantitative estimate of the compositional effects on molecular mobility, was based on the William-Landel-Ferry (WLF) equation., Conclusion: The S concept exhibits considerable potential for application in controlling the crystallization of amorphous maltose and improving the processability and stability of maltose-containing foods. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

[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]