Effect of hydrothermal postharvest treatment on skin ultrastructure of papaya (Carica papaya L.) Pococí hybrid

T. Vargas, M. Jiménez, P. Calvo
In Costa Rica, production and exports of the papaya Pococí hybrid have increased over the last ten years, representing an important income for small farmers. Postharvest hydrothermal treatment is used for pest control and is compulsory to access some markets. It also could be an option for control of diseases and has an effect to delay ripening. However, it may cause dehydration and scalded skin damage. With the objective to evaluate the effect of hydrothermal treatment on skin ultrastructure, the following treatments were applied on Pococí papaya fruits: 1) Control: dipping in chlorine solution, followed by dipping in prochloraz fungicide; 2) Hydrothermal: dipping in hot water (49°C) for 20 min + control treatment; 3) Commercial wax: same as control followed by wax coating; 4) Combination of hydrothermal + commercial wax. Ultrastructure was evaluated using scanning electronic microscopy and making differences between skin which was exposed to direct sun-light during the fruit development on the field, and skin exposed to shade. Evaluations were done before and after cold storage at 14°C, and after shelf life simulation. In the control treatment, epicuticular waxes of the ‘shade side’ had smoother surfaces than the ‘sun-light side’. Treatments 2, 3 and 4 affected the epicuticular waxes of the ‘sun-light side’ making them smoother and more similar to the ‘shade side’ of control fruits. Storage did not affect the epicuticular waxes conformation but the shelf life period in which depressions were observed in treatments 1 and 2. Stomata occlusion was observed in treatments 3 and 4 before cold storage. Nevertheless, stomata occlusion and changes in their epicuticular waxes conformation were not observed after cold storage.
Vargas, T., Jiménez, M. and Calvo, P. (2020). Effect of hydrothermal postharvest treatment on skin ultrastructure of papaya (Carica papaya L.) Pococí hybrid. Acta Hortic. 1278, 19-28
DOI: 10.17660/ActaHortic.2020.1278.4
papaya, postharvest, hydrothermal, wax coating, cold storage, epicuticular wax, stomata

Acta Horticulturae