Effects of organic vs. conventional farming systems on quality and antioxidant metabolism of passion fruit during maturation

- Organic farming tended to show reduced contents of phenolics and acidity.
- Cultivation system did not influence the contents of flavonoids and anthocyanins.
- Vitamin C was highly influenced by cultivation system.
- PAL activity was significantly higher in organic farm, at mature stage.

The objective of this study was to evaluate the changes in quality and antioxidant metabolism during ripening of passion fruits from organic and conventional production systems. Postharvest quality, variables of antioxidant metabolism (enzyme and non-enzymes), total antioxidant activity (TAA), lipid peroxidation degree as indicator of oxidative stress and the activity of phenolic-associated enzyme, phenylalanine ammonia lyase (PAL) were evaluated in fruits harvested at developmental stages: breaker/turning yellow (physiologically mature) and completely yellow color (ripe). Results show that organic fruits were smaller, although with higher soluble solids content and a lower acidity. At breaker stage, PAL activity was 24% than higher in organic fruits than in conventional fruits, although, total phenolic content was higher in conventional fruits harvested at both breaker (36.14 mg GAE 100 g−1) and ripe (36.47 mg GAE 100 g−1) stages. Organic fruit showed a significantly greater lipid peroxidation degree of biological membranes, despite their also higher APX activity and vitamin C contents. Results suggest that organic cropping system induced an oxidative stress in passion fruit, negatively influencing fruit size, although inducing the antioxidant defense mechanism, through increments of vitamin C and antioxidant enzymes activity.