Multi-scale engineering properties of tomato fruits related to harvesting, simulation and textural evaluation

- Geometric mean diameter was most closely correlated with tomato fruit mass.
- Multi-scale geometry of tomatoes showed heterogeneous and anisotropic properties.
- The contribution of exocarp to the hardness of whole fruit increased with ripeness.
- Puncture experiment is suited to measure the multi-scale mechanics of fruit.

In this study, multi-scale engineering properties related to the harvesting, simulation and textural evaluation of two tomato cultivars at six ripening stages were simultaneously investigated. A potential ripening scale based on the ratio of R:G:B for a given ripening stage was suggested. The geometric mean diameter was most closely correlated with the fruit mass. Tomato fruit feature an irregular shape and asymmetric internal structure at the macro-scale, non-unique tissue thickness at the meso-scale and an irregular change of size, shape and arrangement of single cells at the micro-scale. The hardness and shear strength of fruit at different scales and the single cell mechanics varied with the fruit ripening stage but not the chosen cultivars. The contribution of exocarp to the hardness of whole fruit gradually increased with fruit ripeness. The hardness and shear strength of fruit tissues and the fruit's single cells varied between 0.37 and 2.25 MPa and 0.04 and 11.58 MPa, respectively. This puncture experimental method is well-suited to measure the hardness and shear strength of tomato fruit at different scales and single tomato cell mechanics.