Preharvest application of oxalic acid improves antioxidant systems in plums

Fruit ripening is a functionally modified form of senescence, associated with reactive oxygen species (ROS) accumulation, which are inevitably generated in plant cells as a consequence of normal metabolism.
These ROS are scavenged in plant cells by antioxidant compounds (such as phenolics, tocopherols, carotenoids and ascorbic acid) and by antioxidant enzymes including mainly superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX). Thus, occurrence of increased content of antioxidant compounds and antioxidant enzymes could lead to a delay of the fruit postharvest ripening process with beneficial effects on maintaining fruit quality attributes for longer periods.
Previous reports have found that oxalic acid (OA) preharvest treatments increased quality and functional properties in sweet cherries at harvest and along storage.
Thus the aim of this experiment was to evaluate the effect of 1 mM OA treatment of plum trees, Prunus salicina Lindl. ‘Black Splendor’ (applied as foliar spray at three key points of plum fruit development), on fruit properties at harvest as well as in the antioxidant systems, both antioxidant compounds and antioxidant enzymes.
Results showed that OA treatments did not affect the on-tree ripening process of plums and both control and treated fruits were harvested at the same date, according to its characteristic skin color and total soluble solids content.
However, OA treatment showed a significant effect on increasing total phenolics and antioxidant activity, as compared to control fruits, leading to fruit with high bioactive compounds and antioxidant potential at commercial harvest.
The activity of the antioxidant enzymes was also higher in OA treated fruits than in controls at harvest time.
Thus, OA preharvest treatments could be an efficient and natural way to increase the bioactive compounds with beneficial effects of human health as well as the activity of the antioxidant enzymes which would lead to a delay in the over-ripening process and to maintenance of plum quality along storage.

VIII International Postharvest Symposium: Enhancing Supply Chain and Consumer Benefits – Ethical and Technological Issues

M. Serrano, A. Marínez-Esplá, M.J. Giménez, D. Valero, P.J. Zapata, F. Guillén, S. Castillo

phenolics, anthocyanins, antoixidant enzymes, quality

https://doi.org/10.17660/ActaHortic.2018.1194.4