CONICET | Buscador de Institutos y Recursos Humanos

Sunburn is a fruit physiological disorder caused by oxidative stress induced by exposure to excessive solar radiation. This disorder modifies fruit maturity and color parameters, which results in significant losses in marketable fruit. The aim of this work was to characterize the physiological and biochemical changes related to oxidative metabolism in Beurré D´Anjou pear fruit with different levels of sunburn. At harvest, the fruits were collected and graded into different sunburn levels: no sunburn (S0), mild sunburn (S1), and moderate sunburn (S2). Maturity indices were measured on sunburn tissues. Surface color, pigment and total phenol contents, electrolyte leakage, lipid peroxidation, antioxidant capacity, and antioxidant enzyme activities (SOD, APX, and CAT) were determined on the fruit skin. Sunburn tissues had a significant increase in firmness, soluble solids content, and starch degradation, along with lower acidity when compared to S0. Sunburn skin pears showed changes from green to yellow and brown tones with increasing damage, which was associated with chlorophylls content reduction. S1 had the highest amount of anthocyanins (2.74 mg cyn-3-gluc 100 g-1FW), but there were no differences between S2 and S0 (0.05 and 0.37 mg cyn-3-gluc 100 g-1FW, respectively). Electrolyte leakage increased with the damage level, while lipid peroxidation was lower in S0 (6.69 nmol g-1FW) than in S1 (13.31 nmol g-1FW). Increased antioxidant capacity in S1(39.7 %) and S2 (47.7 %) fruit compared to S0 (22.8 %) was related to the higher phenolic content recorded in these tissues. SOD and APX significantly increased their activity in sunburn skin, while CAT activity decreased when compared with S0. These results are consistent with previous apple sunburn reports and show that the sunburn pear exhibits changes in its oxidative metabolism, modifying its quality traits and maturity state.