Effect of cell size distribution on mechanical properties of strawberry fruit tissue

Abstract

Strawberry fruit are high value, but also perishable products, because of their soft texture. Better insight on the strawberry mechanics are requested for understanding postharvest decay due to bruising. To gain data on the volumetric cell size distribution of strawberry tissue capturing the volume of 10 * 5 * 5 mm, fruit cells were suspended in 0.3 M mannitol solution. Cell size of 'Flair', 'Malwina', and 'Sonata' strawberry fruit, each in three commercially marketed ripeness stages (N = 135), was measured with particle size analyzer based on laser light scattering density analysis (LSD). The strawberry cell size distribution showed a wide range from 30–500 µm with frequency peak between 200 and 240 µm. The cell size of 'Flair' and 'Malwina' was smaller compared to 'Sonata' strawberry fruit. The volumetric cell size distribution obtained by LSD was correlated to microscopy results (R2 = 0.97–0.99) obtained on single cells (N = 1215), indicating that LSD can be used for measuring the percentages of different cell size ranges of volumetric fruit sample. The three ripeness stages were classified with Gaussian Naïve Bayes approach considering absorption coefficient of anthocyanins at 405 nm (GNBa) and percentage frequency of peak cell size (GNBc). For GNBa classes, ripening stage showed no interaction with failure stress, strain, and elastic modulus. Considering GNBc classes, the failure stress and elastic modulus of strawberry tissue increased with enhanced percentage frequency of peak cell size for all three cultivars. An enhanced percentage frequency of large cells resulted in increased susceptibility of the strawberry tissue. Overall, this study showed that LSD cell size distribution data from a volumetric tissue sample are related to fruit tissue mechanics, which is conducive to a better analysis of the actual stress and damage problems of strawberry fruit tissue specimens during compression in supply chain processes.