Textural thermo‐mechanical properties of sweet cherry for post‐harvest damage analysis

Development of a new bio-microscope for 3D geometry characterization of fruit single cells

Fruit cells are living irregular three-dimensional (3D) transparent objects which makes them challenging to determine their real 3D size and shape through only two-dimensional (2D) images using the existing biological microscope. This study deals with a newly self-developed biological microscope including a microscope imaging system, a light source system, a stage and a support base for the 3D size characterization of fruit single cells. The main design concept is based on two optical path systems set up at the front (x-axis) and bottom (z-axis) directions of a transparent chamber containing single cells that allow the front view and bottom view of the single cell to be observed. Performance indicators such as mass, size, observation range, objective magnification, total magnification, focal range, focal accuracy, and resolution of the developed biological microscope were estimated. Finally, the 3D geometry size of single tomato cells was measured by the new biological microscope to demonstrate the relative ease at which accurate real 3D geometry information of single fruit cells could be obtained, which echoes its scientific value.

Analysis of the correlation between mesocarp biomechanics and its cell turgor pressure: A combined FEM‐DEM investigation for irrigation‐caused tomato cracking

Fruit mesocarp cracking caused by improper irrigation during development manifests at the macroscale but is ultimately the result of increasing cell turgor pressure at the microscale. Hence, a cell finite element (FE) model including shape, protoplast turgor pressure, and ripening information and a mesocarp tissue block discrete element (DE) model including the features of cell shape and number, were developed to predict the biomechanical correlation between mesocarp and its cell. The validated cell FE model with an internal turgor pressure of 12.9 kPa could reproduce the experimental force-deformation behavior of a single cell in compression up to 11% deformation with an average relative error of 5.8%. The validated mesocarp tissue block DE model could reproduce the experimental force-deformation behavior of a mesocarp block in compression up to 20% deformation with an average relative error of 9.5%. Sensitivity and regression analysis showed that turgor pressure was the most important factor affecting cell biomechanics, followed by cell shape and wall elastic modulus. Similarly, the apparent elastic modulus of the cells has the most significant effect on the mesocarp tissue biomechanics, followed by the number and shape of cells. Finally, a mathematical model was obtained to quantitatively describe the relationship between the elastic modulus of the mesocarp and its cell turgor pressure. This study contributes to a better understanding of the biomechanical mechanisms of irrigation-caused tomato fruit cracking at the cellular level and the development of strategies to prevent fruit cracking through a combination of gene breeding and irrigation management.