Impact of dynamic controlled atmospheres on reactive oxygen species, antioxidant capacity and phytochemical properties of apple peel (cv. Granny Smith)

This study was conducted to investigate the effect of dynamic controlled atmospheres (DCA) on antioxidant capacity, reactive oxygen species (ROS) and phytochemicals in the apple peel of ‘Granny Smith’ harvested at pre-optimal and optimal maturity over two growing seasons. Fruit was stored in DCA (<0.5% O₂; 1% CO₂) for up to 20 w at 0 °C and regular air (RA) was used as a control treatment. Phytochemicals, antioxidant capacity and lipid peroxidation were spectrophotometrically measured. ROS were measured by confocal laser-scanning microscopy on apple peel treated with fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate. Principal component analysis (PCA) and Pearson's correlation were used to investigate major changes and relationship among the studied variables. Fruit stored in DCA were characterized by higher antioxidant capacity, ascorbic acid and total phenolics concentration. However, lipid peroxidation and ROS were significantly lower in DCA stored fruit. PCA displayed two clusters that could easily be identified as DCA and RA stored fruit. Positive correlation scores for lipid peroxidation and ROS corresponded with RA stored fruit whilst strong negative stores for antioxidant capacity, ascorbic acid and total phenolics corresponded with DCA stored fruit. Pearson's correlation showed a strong relationship between ascorbic acid, phenolics and antioxidant capacity. Lipid peroxidation and ROS also showed a significant (p < 0.05) positive correlation. This study showed that the high fruit quality in DCA correlates with higher antioxidant capacity, total phenolics and ascorbic acid concentrations in this fruit.