Nitric oxide reapplication during controlled atmosphere storage impacts on oxidative stress and volatiles production in 'Cripps Pink' apples

The aim of this study was to evaluate the effect of different concentrations of nitric oxide (NO) reapplied during controlled atmosphere (CA) storage on oxidative stress defense mechanisms and on profile of volatile compounds of 'Cripps Pink' apples. Fruit were treated with NO at 0, 1, 2, 5, or 10 μL L−1 every seven days during CA storage (0.8 kPa of O2, <0.5 kPa of CO2, at temperature of 1.5 ± 0.2 °C, and 94 ± 2% RH). Fruit were evaluated after 8 months of CA storage, followed by seven days of shelf life. In general, linear and quadratic models adjusted to quantitative levels of NO showed increased contents of total phenolic compounds (in the pulp and peel tissues), increased activity of catalase, reduced activity of lipoxygenase, reduced content of H2O2, reduced lipid peroxidation and ethylene production in the fruit with the increase of NO concentrations. NO treatment had no effect in the total antioxidant activity and in the activity of the enzymes superoxide dismutase and peroxidase in the fruit. The increase of NO concentrations reduced the volatile compounds butyl acetate, hexyl acetate, 2-methylbutyl acetate, ethyl butanoate, til 2-methylbutanoate, and 1-butanol in the pulp of the fruit. The results show that weekly application of NO at ∼6 μL L−1 during CA storage of 'Cripps Pink' apples improved the mechanisms to protect the fruit from oxidative stress, but it might impair the production of the main esters associated with aroma.