Characterization of textural failure mechanics of strawberry fruit

Abstract

Fresh strawberry fruit is highly susceptible to damage during mechanical handlings. To prevent fruit macro-damage from external forces and predict damage evolution in internal tissues, the textural failure mechanics of strawberry fruit and its tissues were characterized by loading-unloading tests at different compression speeds. Strawberry fruit showed expected three stages of deformation during the loading phase, namely elastic, local plastic and structural failure deformation. Their cut-off points depended on the compression speed and loading direction, which was validated further by the corresponding visible browning processes in tissues from fruit longitudinal equatorial section. The peak force and absorbed energy depended on the loading direction and compression speed while the percentage of damaged mass only depended on the loading direction. The fruit was most susceptible to mechanical damage when it was compressed along its stem-blossom axis at low percentage deformation and along its radial axis at high percentage deformation. The absorbed energy and percentage of damaged mass of the strawberry fruit was correlated, which suggested that the absorbed energy could be an appropriate and easily measurable mechanical parameter for quantitatively assessing the degree of fruit damage. The failure stress, failure energy and elastic modulus of fruit tissues increased with the compression speed, while this factor did not affect the failure strain. The average failure stress, failure strain, failure energy and elastic modulus of fruit inner tissue were 0.093 MPa, 17.7%, 8.09 mJ, 0.53 MPa, which was 1.27, 1.14, 1.47, 1.15 times enhanced compared to values of outer tissue (p < 0.05), respectively.