Influence of 1-Methylcyclopropene and Geranium Oil Treatments on Oxidative Stress and Antioxidant Enzyme Activity in Carica papaya L. During Cold Storage

Carica papaya Linn, known for its limited shelf life, typically relies on conventional cold storage (CS) methods to prolong freshness. However, being a fruit sensitive to chilling, papaya exhibits low tolerance to cold conditions, making it susceptible to chilling injury during CS. This study was undertaken to explore the correlation between postharvest treatment using 1-methylcyclopropene (1-MCP) and geranium oil (GO) and the antioxidant responses of papaya against oxidative stress during CS. Various treatments were administered, incorporating different concentrations and durations of exposure. The specified concentrations for 1-MCP and GO were 300 and 600 mg/L, and 2% and 4% (v/v), respectively, with exposure durations of 30 and 60 min. Over a 16-day period, the fruits underwent assessments for antioxidant activity, related enzyme activities, hydrogen peroxide content, and superoxide anion production rate at 4-day intervals. Both 1-MCP and GO treatments enhanced total phenolic and total flavonoid content, DPPH scavenging antioxidant capacity, and notably improved the activities of SOD, CAT, APX, and POD enzymes. This enhancement in antioxidant capacity and enzyme activities effectively mitigated the rise in reactive oxygen species levels in the fruits. The study revealed that 1-MCP treatment with higher doses and longer exposure times yielded superior outcomes, while GO treatment with higher doses and shorter exposure times produced favorable results compared to longer exposure times. Considering cost-effectiveness and time efficiency, a more comprehensive exploration of the synergistic effects of 1-MCP and GO may be essential to optimize effective doses within a reduced exposure timeframe.