University of California

Fruit English

Longan

Recommendations for Maintaining Postharvest Quality

Longan

Adel A. Kader

Department of Plant Sciences, University of California, Davis 

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 20g
  • 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

Maturity & Quality Photos

Longan_quality

Title: Quality

Photo Credit: Adel Kader, UC Davis

Temperature & Controlled Atmosphere

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.

Disorders

Physiological and Physical Disorders
Chilling injury. Symptoms include darkening of the skin color and increased susceptibility to decay. Also, some loss of flavor of the arils may occur.

Skin darkening. Skin changes from light brown to dark brown as a result of water stress (desiccation) of longan.

Pathological Disorders

Decay-inducing fungi include Lasiodiplodia theobromae, Aspergillus niger, Cladosporium sp, and Fusarium sp. Decay control can be achieved by reducing physical injuries and proper management of temperature and relative humidity during postharvest handling. Sulfur dioxide treatment may be used in some countries to prevent skin darkening and control postharvest diseases of longan, but this treatment may result in undesirable taste and is not allowed on longan marketed in the U.S.A.

Date

May 2001

Use of Materials

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How to Cite

Author(s) names. Initial publication or update date (located at the top). Title. Link to the specific Produce Fact Sheet webpage (Accessed date)

Example: Cantwell, M. and T. Suslow. 2002. Lettuce, Crisphead: Recommendations for Maintaining Postharvest Quality. 

http://ucanr.edu/sites/Postharvest_Technology_Center_/Commodity_Resources/Fact_Sheets/Datastores/Vegetables_English/?uid=19&ds=799 (Accessed January 18, 2014).

College of Agricultural & Environmental Sciences
Postharvest Technology Center
Department of Plant Sciences

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