Effect of CO2 deastringency treatment on flesh disorders induced by mechanical damage in persimmon. Biochemical and microstructural studies

Manifestation of flesh browning while commercialising 'Rojo Brillante' persimmon is one of the main causes of postharvest loss. It is known that mechanical damage is a decisive factor for browning development and that astringent fruit is less sensitive to this disorder than fruit submitted to a CO2 deastringency treatment under standard conditions (24 h, 95% CO2, 20 °C). However, there is no information available about the mechanism behind this alteration. In the present study, we evaluated the effect of treatment with high CO2 concentrations applied for 0-40 h on the incidence of mechanical impact-induced flesh disorders using biochemical, chromatographic and microstructural techniques. Our results show that the longer the CO2 exposure, the higher the incidence and the greater the severity browning. A deastringency treatment with CO2 results in O2- accumulation in fruit, which is greater the longer treatment is. However, mechanical damage triggers the browning manifestation, resulting in the accumulation of both O2- and H2O2. In this oxidative stress state, which must be greater as higher the level of O2- previously accumulated in the deastringency treatment, insoluble tannins initially uncolour, undergo an oxidation process and turn red-brown, observed as flesh browning. Moreover, we identified a new disorder, “pinkish-bruising”, which is manifested in astringent fruit. The mechanism of this alteration, also associated with mechanical damage, seems similar to that of browning, but the oxidation process would affect soluble tannins.