Characterisation of mechanical properties of food materials during drying using nanoindentation

The microstructure of plant-based food materials (PBFM) is mostly composed of assemblies of irregular cellular compartments. Dynamically changing mechanical properties play a vital role in the drying kinetics, deformation, and the quality attributes of PBFM. Therefore, understanding the micro-level mechanical properties and their relationships with the moisture loss during food drying is essential. However, research on this filed has rarely been attempted. This research aims to investigate the micro-level mechanical properties of PBFM during drying and establish a set of relationships between the elastic modulus, hardness, and stiffness and the moisture content. Nanoindentation experiments were performed using Hysitron TI-950 TriboIndenter at different stages of drying. It was found that the mechanical properties remained quite steady at early stages of drying, which were significantly increased at the later stages of drying. This study established the essential relationships among different micro-mechanical properties of PBFM and moisture content during drying.