Pseudomonas graminis strain CPA-7 differentially modulates the oxidative response in fresh-cut ‘Golden delicious’ apple depending on the storage conditions

Abstract

The oxidative response in fresh-cut antioxidant-treated‘Golden delicious’apples during chilling storage wasdifferentially modified by the biopreservative bacteriumPseudomonas graminisCPA-7 depending on the storageconditions (passive modified atmosphere packaging (MAP) or air). Results showed that inoculation with CPA-7had no influence on fruit quality parameters in any of the conditions tested. During thefirst 24 h both in air andin MAP, ascorbate peroxidase (APX) activity triplicated the initial level in response to CPA-7, reaching up to 4-fold the activity of non-inoculated fruit (control). From 24 h of storage in MAP, polyphenol oxidase (PPO)activity was sharply enhanced in response to CPA-7 attaining values up to 8-fold higher than that of the controlat the end of the experiment, yet it was not paired to an increase in browning incidence. Concomitantly, at 24 hof storage in MAP, CPA-7 suppressed peroxidase (POX) and catalase (CAT) activities. Subsequently, after 3 d insuch conditions, superoxide dismutase (SOD) and PPO activities were almost duplicated in the presence of CPA-7compared to the control. On the other hand, when stored in air, POX showed a biphasic induction in response toCPA-7 after 1 d and 6 d of incubation. On day 6, this enzyme duplicated its activity in inoculated samplescompared to the control regardless of storage conditions. Inoculation with CPA-7 led to the slowdown of thedecline of antioxidant capacity in air, which contrasted with the response upon MAP conditions. These resultssuggest that CPA-7 may trigger the activation of the fruit defense-response thereby mitigating its oxidativedamage. Such activation may play a role as a putative biocontrol mechanism against foodborne pathogen in-fections.