After picking, longan has high Breathing, is prone to browning, and spoils fast. Controlled atmosphere (CA) storage, with cold and damp conditions, can significantly extend the shelf life. The process has five main steps: pre-harvest care, initial cooling, CA setting, daily upkeep, and final control. Longan Controlled-Atmosphere Cold Storage is critical in handling these issues after harvest. In fact, Longan Controlled-Atmosphere Cold Storage represents a best practice for keeping produce fresh after picking worldwide.
1. Harvesting
Prioritize fruit at 80–90% maturity that is free from mechanical damage, diseases, and pests. Pick fruit with short stems attached to avoid skin breakage and juice leakage. Complete freshness keeper treatment within two hours of harvest: immerse the fruit in 52°C water for two minutes to eliminate Colletotrichum fungi on the skin. Next, there is a one-minute dip in a citric acid or food-grade chitosan solution. After drying the surface and removing cracked, diseased, or unripe fruit, pack the produce into ventilated plastic crates. Stack these crates in a single layer to prevent compression damage. This attention to pre-storage quality ensures the best results from Longan Controlled-Atmosphere Cold Storage.
2. Before storage
Disinfect the controlled-atmosphere (CA) chamber with ozone to eliminate residual ethylene and microorganisms. The fruit undergoes rapid pre-cooling, with the core temperature lowered to 3–4°C within 24 hours. During this phase, the chamber doors remain open to dissipate field heat. This practice prevents sealing the fruit while still hot, thereby avoiding condensation and subsequent mold growth.
Once you complete pre-cooling, seal the chamber, and activate the nitrogen generation and CO₂ removal systems to regulate gas levels. The control system stabilizes oxygen at 6%–8% and carbon dioxide at 4%–6%. CO₂ levels must strictly remain below 10% to avoid off-flavors and intensified flesh browning.
The storage system maintains a constant temperature of 2–4°C (with fluctuations not exceeding ±0.5°C) and relative humidity of 90%–95% using a high-pressure micro-mist humidification system. Direct cold airflow to avoid blowing directly onto the fruit stacks. This practice minimizes moisture loss and skin shriveling.
Notably, Longan Controlled-Atmosphere Cold Storage helps achieve optimal results for skin condition and pulp freshness throughout this critical storage phase.
3. During Longan cold storage
Workers monitor gas composition, temperature, and humidity hourly during storage. If concentration deviations exceed 0.5%, quickly restock N₂ or remove carbon dioxide. The ethylene removal system maintains in-storage ethylene levels below 0.01 ppm. Do not store longan with apples or mangoes; they speed up aging. Maintain ventilation channels within the fruit stacks, and conduct sampling inspections every seven days. These inspections focus on skin browning, pulp fermentation, and mold growth. Workers promptly sort out and isolate any spoiled fruit they detect during inspections. This system delivers a stable storage period of 35–40 days for longans, achieving a high-quality fruit rate exceeding 93% under standard operating conditions. This outcome significantly outperforms the 10–15 day shelf life typical of conventional cold storage. Certainly, Longan Controlled-Atmosphere Cold Storage delivers improved shelf life when compared to traditional methods.
4. Before removal from Longan cold storage
Before removal from storage, phase out the controlled atmosphere by slowly introducing air to displace the low-oxygen environment. Raise the temperature to approximately 10°C prior to handling to prevent rapid skin blackening caused by sudden temperature fluctuations. Never keep it in high CO₂ for too long. Additionally, loading volumes are controlled and air circulation channels are maintained to ensure uniform distribution of temperature, gas, and humidity. As a result, the preservation of the longan's sweet, fresh pulp flavor and the integrity of its skin is maximized.
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