Regulation of Ascorbic Acid Metabolism in Postharvest Navel Orange Fruit During Storage by Exogenous Hydrogen Sulfide

Why It Matters

By stabilizing vitamin C levels, H₂S treatment boosts the health value and marketability of oranges, offering growers a low‑cost tool to extend shelf life and command premium prices.

Key Takeaways

• H2S fumigation slows weight loss in stored oranges
• Vitamin C decline reduced by ~30% over 18 days
• Biosynthesis genes up‑regulated, degradation genes down‑regulated
• Treatment maintained soluble solids and acidity levels
• H2S acts via L‑galactose pathway to boost AsA

Pulse Analysis

Postharvest degradation of ascorbic acid is a major quality challenge for citrus producers, because vitamin C content can drop sharply within weeks, eroding nutritional value and market price. Recent studies have highlighted hydrogen sulfide (H₂S) as a low‑concentration gaseous signal that can extend shelf life in a variety of fruits, yet its impact on the vitamin C pathway remained unclear. The new research demonstrates that a brief 30‑minute exposure to 25 µL L⁻¹ H₂S preserves both the visual and biochemical integrity of navel oranges stored at ambient temperature for 18 days, offering a practical, non‑chemical intervention for growers.

At the molecular level, H₂S orchestrates a coordinated shift in the L‑galactose ascorbate biosynthesis route. Genes such as CitPGI, CitPMM, CitGME, and CitGGP show marked up‑regulation, while the key degradation gene CitAO is suppressed, collectively driving a net increase in total ascorbate. Parallel activation of regeneration enzymes CitMDHAR and CitGR further recycles oxidized forms, sustaining the vitamin pool. This gene‑level control mirrors stress‑responsive pathways in other crops, suggesting that H₂S can be integrated into existing postharvest protocols without altering conventional handling practices.

The commercial implications are significant: maintaining higher vitamin C levels can command premium pricing and meet rising consumer demand for nutrient‑dense produce. Because the treatment uses a gaseous agent at concentrations far below toxicity thresholds, it avoids residue concerns associated with synthetic preservatives. Moreover, the approach could be adapted to other high‑ascorbate fruits such as strawberries and kiwifruit, expanding its market relevance. Ongoing research should explore optimal dosing, storage temperature interactions, and scalability, positioning H₂S fumigation as a next‑generation tool in the fresh‑produce supply chain.