Preharvest melatonin application alleviates red drupelet reversion, improves antioxidant potential and maintains postharvest quality of ‘Elvira’ blackberry

Abstract

Blackberry (Rubus spp.) is susceptible to red drupelet reversion (RDR) during postharvest supply chain which has been associated with anthocyanin degradation. The efficacy of preharvest melatonin spray application (0, 50, 100 and 200 µmol L−1) two weeks before anticipated harvest on RDR, anthocyanin degradation, antioxidant capacity and postharvest quality of blackberries was investigated. Following the harvest, the blackberry fruit was stored at 2 ± 1 °C and 85–90 % relative humidity up to 12 d. Blackberries sprayed with 100 µmol L−1 melatonin mitigated RDR (40.9 %), reduced weight loss (44.8 %) and fruit decay (FD) (24.6 %) as compared to control. Melatonin spray application (100 µmol L−1) significantly delayed the degradation of total anthocyanins, glutathione (GSH), ascorbic acid (AsA) and 2, 2-diphenyl-1-picrylhydrazile (DPPH) radical scavenging in cold stored blackberries. Similarly, fruit treated with 100 µmol L−1 melatonin expressed higher activities of antioxidant enzymes including glutathione reductase (GR), catalase (CAT), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and ascorbate peroxidase (APX). Conversely, fruit treated with 50 µmol L−1 melatonin improved soluble solids content (SSC), total flavonoids, phenolics, carotenoids and activity of superoxide dismutase (SOD). In addition, melatonin spray applications considerably reduced malondialdehyde (MDA), hydrogen peroxide radicals (H2O2), total chlorophyll, and activity of polyphenol oxidase (PPO) during the entire period of storage. In conclusion, melatonin spray application (100 µmol L−1) two weeks before anticipated harvest alleviated RDR in blackberry fruit by improving antioxidant potential and retaining better postharvest quality for 12 d of cold storage.