Micromechanical characterization of a wheat-based food material as a function of moisture content

The microstructural changes in food materials during the baking process directly influence their micromechanical properties and, thus, the strength of the solid walls. Baking time, as one of the vital variables, impacts the microstructural and micromechanical characteristics, alters the texture, and affects customer satisfaction. This research aims to investigate the alteration in three critical micromechanical properties: hardness, stiffness, and Young’s modulus, as a function of moisture content during baking of cookies in an oven set at 185 ± 1 °C in the range of 10 to 60-min. The nanoindentation method, which involves pushing a nanoindenter into and removing it from cookie samples to measure the force-displacement data, was employed to measure the micromechanical properties. The results indicated that all the micromechanical properties initially increased when the moisture content decreased from 12.26 to 8.53 g/100 g solids and showed fluctuating trends at the later moisture content values. Throughout the baking process, the moisture content ranges from 2.71 to 12.26 g/100 g solids. Simultaneously, hardness varies from 0.28 to 0.88 GPa, stiffness ranges between 9.77 and 20.16 µN/nm, and Young’s modulus experiences minimum and maximum values of 4.34 and 14.55 GPa, respectively. Finally, the Analysis of Variance and Duncan’s multiple range tests revealed a significant difference between the mean values of some data points of hardness, stiffness, and Young’s modulus as a function of moisture content.