Total phenol and quercetin content and antioxidant activity in apples in response to thermal, light stress and to organic management

Abstract

Flavonoids are the most abundant phenol compound group in apples, the concentration of which varies with the cultivars and climatic conditions. The objective of this study was to evaluate the effects of temperature, solar radiation, sunburn damage of the peel and the state of development of fruit on total phenol concentrations, quercetin glycosides and antioxidant activity. Three assays were conducted during the 2008/09 season to evaluate aforementioned variables on these parameters. The following season, the effect of the state of development on the fruit was evaluated. Sunburn increased phenol concentrations from 5.5 to 8.7 mg CAE* g FW^-1. In relation to the state of development of the fruit, phenol concentrations decreased from 14 to 1.3 mg CAE* g FW^-1 between 32 DAFB to harvest, respectively.  Fruit that was bagged until one month before harvest had significantly higher concentrations of quercetin rutinoside (28 mg*g^-1FW), galactoside (484 mg*g^-1FW) and glucoside (54 mg*g^-1FW) than fruit that remained bagged until harvest (6, 161 and 21 mg*g^-1FW, respectively). Temperature did influence phenol concentrations. This study determined that sunburn, the state of development and bagging the fruit are factors that determine phenol concentration in apples.