Sunburn on apples is associated with increases in phenolic compounds and antioxidant activity as a function of the cultivar and areas of the fruit.

摘要

Sun-damage (sunburn) in apples is one of the main causes in Chile for rejection of apples for export cultivated in areas with high temperatures and high levels of sunlight. The objective of this study was to determine the effect of increasing levels of sunburn on the peel (exocarp) and flesh (mesocarp) of different apple cultivars (cvs) in terms of pigment, phenolics content and antioxidant activity. During 2006/2007 to 2008/2009 seasons two assays were carried out: (1) concentration of total phenolics and total antioxidant activity in the peels of cvs Fuji, Braeburn and Granny Smith, with and without sunburn; and (2) pigments (chlorophylls, carotenoids and anthocyanins), total phenolics, total antioxidant activity and quercetins (Q) in different areas of the peel and flesh of cv Fuji apples. The antioxidant activity in apple peel on the exposed side at severe (SL2) (11.7+or-2.4 mg g-1 FW) and moderate levels of damage (SL1) (11.2+or-0.9 mg g-1 FW) was significantly higher than that found in peel of undamaged or healthy fruit (SL0) exposed to direct sunlight (7.0+or-0.9 mg g-1 FW). The same relationship for sun-damaged and un-damaged tissue was observed in the concentration of phenolics. The concentration of Q glycosylates in the peel of Fuji apples with SL2 and SL1 damage at both the center of the exposed side and its surroundings was significantly higher than that of the unexposed side. Q galactoside presented the highest concentration in both healthy and damaged fruit. Q glucoside showed the highest increase in sun-damaged fruit, while Q arabinoside decreased in relative terms. A decrease in chlorophylls and anthocyanins, and an increase in carotenoids were also observed in sun-damaged fruit. The fact that sun-damaged apples presented a higher concentration of phenolic compounds and antioxidant activity, given the favorable effects of these on human health, represents an alternative commercial opportunity.