Relationship of Cell Size Distribution and Biomechanics of Strawberry Fruit Under Varying Ca and N Supply

Bruising due to compression of strawberry fruit is the major cause for fruit decay, resulting in food waste, which can be observed macroscopically as the result of texture failures. In the present study, laser light scattering density (LSD) analysis was applied to study the effect of cell size distribution percentages on fruit mechanics, considering three growth stages and added variance by foliar spray application of Ca, N, and Ca-N. The growth rate k considering cell size range 300–450 µm was enhanced in N compared to Ca treatment with 0.8 and 0.5, respectively. Comparison of cell sizes and mechanical fruit tissue properties reveals a strong effect of cell size on fruit mechanics. Based on cell size data, the particles in discrete element models (DEM) were established, applying a simple contact model of Hertz-Mindlin to test the effect of LSD data input, when simulating the compression peak force of strawberry tissue. Comparing measured compression data and DEM simulation, the mean square error was reduced, e.g., for Ca group of over-ripe fruit, from 9.6 to 6.5% when LSD percentages of cell size distribution were considered. Concluding, the newly available cell size distribution data provide valuable information on fruit growth and enable the simulation of fruit tissue compression under varying environmental growth conditions. The enhanced simulation accuracy of LSD-DEM approach makes the approach relevant for plant nutrition, developing robot harvesters, sorting devices, and shelf life assessment of fresh fruit.