Determination of cell wall elastic modulus using a micro-mechanical compression model of apple tissue
The mechanical properties of fruit tissue determine quality attributes such as firmness, and susceptibility to mechanical damage. Fruit tissue is a heterogeneous material, composed of a microscopic cell wall network under tension by turgid cells. Consequently, the mechanics of the cell wall network determines to a large extent the mechanical properties of the tissue. However, measurement of the cell wall properties in situ is difficult and a large uncertainty exists about the value of the cell wall's elastic modulus. In this contribution, a methodology is presented to estimate the elastic modulus using computer models of the histology of tissue. Compression experiments were performed in silico using a hygro-mechanical model that computes the stress development and water loss in the cellular tissue during deformation in the compression test. The elastic modulus of cell walls was estimated by fitting the simulated stress-strain curves to experimental curves of apple parenchyma tissue. Using the model, the effect of different parameters (turgor pressure, microstructure, permeability, wall thickness and damping) on the compressibility of the tissue was then also simulated. Compression resistance of apple parenchyma increases with increasing turgor pressure and thickness of the cell wall, and decreasing cell size and porosity. Microstructure variation of tissues is significant and affects results more than other model parameters. Microstructure varies considerably within cultivars, thus making differences between genotypes more difficult to interpret.
Abera, M.K., Verboven, P. and Nicolai, B. (2017). Determination of cell wall elastic modulus using a micro-mechanical compression model of apple tissue. Acta Hortic. 1182, 275-280
virtual tissue generator, hygro-mechanical model, postharvest technology, hydraulic permeability, turgor