Cuticle changes during tomato fruit postharvest: Implications of natural variability in biophysical properties

The plant cuticle acts as the first protective layer against external biotic and abiotic factors. As such it plays a role during postharvest regulating fruit quality and shelf-life. This study is focused on understanding the changes naturally occurring in the fruit cuticle of two tomato cultivars during postharvest at ambient temperature. A notable decrease in the amount of cuticle and all its components, causing cuticle thinning and a loss of invagination, was observed along storage. This was accompanied by an increase in fruit water loss, cuticle permeability and mechanical weakening, mainly due to a decrease in the elastic modulus and the force needed to break the cuticle. Important differences in the glass transition temperature of the cuticle were observed between both cultivars, with ‘Gardener’s Delight’ exhibiting a temperature around 25–30ºC and ‘Moneymaker’ about 8ºC. These differences have implications in the optimal storage conditions and affect the mechanical and hydrodynamical properties. Thermal properties were not affected by the loss of cuticle material during postharvest. ATR-FTIR analysis of the cuticles allowed the identification of band ratios associated with phenolic enrichment of the cutin matrix and with the proportion of flavonoids present in the phenolic fraction. Comparison between both cultivars suggests that, whereas a cuticle richer in phenolic compounds would contribute to the hydrogen bond network of the cuticle, reduce the esterification index of the cutin matrix, and increase the glass transition temperature, the flavonoid fraction would confer mechanical reinforcement to the cuticle. • Tomato fruit cuticle degrades during postharvest at ambient temperature. • Postharvest affects the hydric and mechanical properties of the cuticle. • The glass transition temperature of the cuticle is cultivar dependent. • Phenolics alter the hydrogen bond network changing the glass transition temperature. • Phenolic enrichment of the cuticle can be estimated with an FTIR band ratio.