Melatonin immersion improves postharvest quality and antioxidant capacity of ‘Nam Dok Mai’ mangoes during storage at ambient temperature

Abstract

Importance of the work: Quality loss and delays in ripening in mangoes were explored based
on melatonin (MT) immersion as a natural, effective postharvest treatment under ambient conditions.
Objectives: To evaluate MT efficacy in preserving the quality, delaying ripening and
enhancing oxidative stress resistance in mangoes under ambient storage.
Materials and Methods: The mangoes were immersed in water (control) or in a solution of
0.5 mM MT for 1 hr and thereafter stored at room temperature for 10 days.
Results: Mangoes treated with 0.5 mM MT had nearly 17% and 60% lower respiration rates
and ethylene production, respectively, than untreated ones at the climacteric peak during
storage, contributing to a slower ripening process and delayed progression of both peel and
pulp coloration. In terms of internal quality, MT application effectively slowed the decline in
firmness, suppressed the rise in the total soluble solids-to-titratable acidity ratio. In addition,
the MT-treated fruits had enhanced antioxidant defense, as shown by elevated activities of
superoxide dismutase, catalase and ascorbate peroxidase. These responses were accompanied
by significantly lower levels of hydrogen peroxide, malondialdehyde and lipoxygenase activity,
suggesting reduced oxidative membrane damage. Collectively, these findings demonstrated that
MT immersion contributed to better quality preservation and improved resistance to postharvest
deterioration and disease through modulation of oxidative stress and antioxidant metabolism.
Main finding: Subjecting mangoes to postharvest MT treatment was a feasible approach
to preserve their postharvest quality and to stimulate antioxidant capability