Effect of Controlled Atmosphere Storage (CAS) on Antioxidant Enzymes and DPPH- Radical Scavenging Activity of Mango ( Mangifera indica L.) cv. Alphonso

Alphonso mangoes ( Mangifera indica L.) pre-treated with either N-propyl-N-[2- (2,4,6-trichlorophenoxy) ethyl] imidazole-1-carboxamide (prochloraz) or hot water (HW) were stored under controlled atmosphere (CA) consisting of 5% O2 and 5% CO2 for 45 days at 8ºC followed by ripening at ambient conditions. Pre-treatments had a pronounced effect on storage life as well as disease incidence. Untreated fruits stored in CA were completely rotten. Irrespective of pre-treatments fruits stored in air showed chilling injury (CI) symptoms during storage at 8ºC and intensity further increased during ripening. Prochloraz or HW pre-treatment followed by CA storage resulted in fruits absolutely free from morphological CI with fresh appearance, hard, green and ripened normally when shifted to ambient conditions (24-29º C, 60-70% RH). Effect of pre-treatments and CA storage on antioxidant enzymes viz. catalase (CAT) peroxidase (POX) and superoxide dismutase (SOD) was compared. The unripe air stored fruits (untreated, prochloraz treated and HW-treated) after 45 days of storage at 8º C showed significantly higher CAT and SOD activity and lower POX activity in comparison to that stored in CA (prochloraz and hot water treated fruits). Freshly harvested matured green fruits showed comparatively less CAT activity than pretreated and stored fruits. Unripe, prochloraz and HW-pretreated fruits of CA storage and freshly harvested fruits have shown similar SOD activity. After 45 days of CA storage at 8ºC, POX activity in prochloraz and HW-treated fruits was higher than that found in freshly harvested fruits. After ripening under ambient conditions, prochloraz and HW-treated fruits stored in both CA and air showed significantly higher antioxidant enzyme (CAT, POX and SOD) activities than corresponding untreated fruits. Total phenol content and 2, 2-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of fruits decreased during CA storage and after ripening when compared to freshly harvested fruits. Decrease was also significant between unripe and ripened fruits of different treatments. Prochloraz or HW-treated fruits stored in CA had highest carotenoids content compared to fruits stored in air after they were ripened at ambient conditions. The present study revealed that CA storage helped in retaining the antioxidant levels of Alphonso mangoes when they were pretreated with prochloraz or hot water.