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Starfruit (Carambola)

Recommendations for Maintaining Postharvest Quality


Adel A. Kader
Department of Plant Sciences, University of California, Davis

Maturity & Quality

Maturity Indices

Fruit color changes from green to yellow which is accompanied by an increase in soluble solids including sugars (sweetness). Carambolas should be picked when fully yellow to assure good eating quality. However, color break (1/2 to 3/4 of fruit is yellow) is used as the commercial maturity index because these fruits are firmer and easier to handle.

Quality Indices

  • Yellow and firm fruits with no brown discoloration on the skin and the five ribs
  • Crisp and juicy flesh
  • Cultivars vary in their sweetness (glucose, fructose and sucrose) and acidity (oxalic and malic acids); sweet (pH = 3.8-4.1) cultivars include ‘Arkin’ and tart (pH = 2.2-2.6) cultivars include ‘Golden Star’
  • Freedom from bruises, insect damage, bird damage, windscar, and decay
  • Carambola fruits are good sources of vitamins A and C

Maturity & Quality Photos

Title: Cross Section

Photo Credit: Adel Kader, UC Davis 

Title: Quality

Photo Credit: Adel Kader, UC Davis 

Temperature & Controlled Atmosphere

Optimum Temperature

5-10°C (41-50°F), depending on cultivar and production area.
Lower temperature may induce chilling injury depending on cultivar, ripeness stage, and temperature and duration of storage.

Optimum Relative Humidity

Lower humidity results in more severe symptoms of rib browning.

Rates of Respiration

Temperature 5°C (41°F) 10°C (50°F) 15°C (59°F) 20°C (68°F)
ml CO2/kg·hr 5-10 8-15 12-18 20-40

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 1.0 µl/kg·hr at 20°C (68°F)
Carambola is a nonclimacteric fruit.

Responses to Ethylene

Green color of carambolas continues to disappear during storage at 15°C (59°F) or 20°C (68°F) and some improvement in flavor due to loss of acidity may be noted. These changes can be slightly accelerated with exposure to ethylene (100 ppm for 24 hours), but such treatment may increase decay incidence and severity.

Responses to Controlled Atmospheres (CA)

Florida carambolas can be kept in air at 5°C (41°F) for 4 to 6 weeks provided that water loss is minimized (by high relative humidity and/or packaging film barriers).There are no published data on their response to atmospheric modification.


Physiological and Physical Disorders

Chilling injury. Symptoms include surface pitting [pits are either small (
Physical Injury. Rib-edge browning and stem-end browning can result from surface abrasions and other types of bruising. The browning intensity increases with water loss from the fruits. Handling carambolas with care to minimize bruising is essential to reducing postharvest losses.

Shriveling. Symptoms become visible when the carambolas lose about 5% or greater of their weight due to water stress.

Heat damage. Skin browning and flesh softening may occur when carambolas are exposed to heat treatments [such as 46°C (115°F) for 35 to 55 minutes] for insect control to satisfy quarantine requirements. Better alternatives may be cold treatment and/or irradiation.

Pathological Disorders

Postharvest diseases of carambolas may be caused by Altenraria alternata (especially on chilled fruits), Cladosporium cladosporioides, or Botryodiplodia theobromae. These usually occur at physically-damaged sites on the fruits during prolonged storage. Minimizing physical damage throughout the harvesting and postharvest handling operations and prompt cooling to 5°C (41°F) can greatly reduce incidence and severity of postharvest diseases on carambolas.


February 1998

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The information in this fact sheet represents our best understanding of the current state of knowledge at the time of the latest update, and does not represent an exhaustive review of all research results. Links to any of these UC Postharvest Technology Center pages are permitted, but no endorsement of the linking site or products mentioned in the linking page is intended or implied by such a link.

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. (Accessed January 18, 2014).

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