The role of auxin in the fruit-ripening process during the early developmental stages of commercial strawberry fruits (Fragaria x ananassa) has been previously described, with auxin production occurring in achenes and moving to the receptacle. Additionally, fruit softening is a consequence of the depolymerization and solubilization of cell wall components produced by the action of a group of proteins and enzymes. The aim of this study was to compare the effect of exogenous auxin treatment on the physiological properties of the cell wall-associated polysaccharide contents of strawberry fruits. We combined thermogravimetric (TG) analysis with analyses of the mRNA abundance, enzymatic activity, and physiological characteristics related to the cell wall. The samples did not show a change in fruit firmness at 48 h post-treatment; by contrast, we showed changes in the cell wall stability based on TG and differential thermogravimetric (DTG) analysis curves. Less degradation of the cell wall polymers was observed after auxin treatment at 48 h post-treatment. The results of our study indicate that auxin treatment delays the cell wall disassembly process in strawberries.

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During the ripening process of fruit, the solubilization and depolymerization of cell wall components takes place, which results in the loss of firmness or the softening of fruit. Recently, we reported that two different strawberry cultivars (“Cristal” and “Portola”) exhibit differences in their fruit softening values, with “Cristal” being the firmest and “Portola” being the softest. In the present work, we performed a comparative study of the changes in the physicochemical properties of the cell wall-associated polysaccharide contents of these two strawberry fruit cultivars via thermogravimetric analysis (TGA), combined with the first derivative of the thermogram (DTG) curves and morphological studies using scanning electron microscopy (SEM). The “Cristal” sample showed higher thermal stability than the “Portola” sample. Additionally, differences were observed between the “Cristal” and “Portola” samples at different stages, principally in Region II (temperatures between 200 °C and 350 °C), with a higher thermal stability evident in the green stage of the two cultivars. Notably, a higher thermal stability was observed in the green stage of the “Portola” sample. The highest percentage of cumulative depolymerization (PCD) was observed in the ripe stage of the “Portola” sample. The DTG curve showed four maximum peaks of degradation, which occurred between 170 °C and 350 °C. Finally, the existence of a relationship between fruit firmness and thermal stability was demonstrated for the two cultivars. This relationship was based on the morphological studies conducted using SEM, which provided new evidence through which to understand the changes within the cell wall polymers of these two strawberry cultivars during the ripening process.

Abscisic acid (ABA) has been proposed to play a significant role in the ripening of nonclimacteric fruit, stomatal opening, and response to abiotic stresses in plants, which can adversely affect crop growth and productivity. The biological effects of ABA are dependent on its concentration and signal transduction pathways. However, due to its susceptibility to the environment, it is essential to find a suitable biotechnological approach to coat ABA for its application. One promising approach is to utilize alginate and chitosan, two natural polysaccharides known for their strong affinity for water and their ability to act as coating agents. In this study, an alginate–chitosan blend was employed to develop an ABA cover. To achieve this, an alginate–chitosan–abscisic acid (ALG–CS–ABA) blend was prepared by forming ionic bonds or complexes with calcium ions, or through dual cross-linking. This was done by dripping a homogeneous solution of alginate–chitosan and ABA into a calcium chloride solution, resulting in the formation of the blend. By combining the unique properties of alginate, chitosan, and ABA, the resulting ALG–CS–ABA blend can potentially offer enhanced stability, controlled release, and improved protection of ABA. These characteristics make it a promising biotechnological approach for various applications, including the targeted delivery of ABA in agricultural practices or in the development of innovative plant-based products. Further evaluation and characterization of the ALG–CS–ABA blend will provide valuable insights into its potential applications in the fields of biomedicine, agriculture, and tissue engineering.