Longan

MATURITY & QUALITY

Maturity Indices

Longan fruit should be harvested ripe for best eating quality. They are harvested and marketed as clusters when the skin becomes smooth and its color changes to yellowish brown or light brown (depending on the cultivar). A minimum of 20% soluble solids may be used as a maturity index.

Quality Indices

• Longan fruit vary in weight from 5 to 20 g, with a smooth, thin, leathery, light-brown pericarp (skin)
• The aril (edible portion) is white surrounding a dark-brown or black seed
• Soluble solids content ranges from 18 to 22% and titratable acidity is low (pH = 6.2 to 6.7)
• Larger fruit that are free from defects (skin blemishes, insect damage) are preferred by consumers

TEMPERATURE & CONTROLLED ATMOSPHERE (CA)

Optimum Temperature

5 ± 1°C (41 ± 2°F); storage potential = 2-4 weeks, depending on cultivar

Optimum Relative Humidity

90 – 95%. Maintaining high humidity and packaging to reduce water loss are very important in preventing skin color changes to dull, dark brown.

Rates of Respiration

8-12 ml CO₂/kg·hr at 10°C (50°F); 15-25 ml CO₂/kg·hr at 20°C (68°F);non-climacteric respiratory pattern

To calculate heat production multiply ml CO₂/kg·hr by 440 to get Btu/ton/day or by 122 to get kcal/metric ton/day.

Rates of Ethylene Production

Less than 0.1 µl C₂H₄/ kg·hr at 20°C (68°F)

Responses to Ethylene

No published information

Responses to Controlled Atmospheres (CA)

Based on the limited published information, a CA combination of 3% O₂ + 5% CO₂ is effective in delaying skin browning and maintaining quality of longan fruit kept at 4°C for 35 days. Modified atmosphere packaging that results in 2-3% O₂ and up to 5% CO₂ is also effective in reducing water loss and associated darkening of the skin.