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Recommendations for Maintaining Postharvest Quality

Carlos H. Crisosto, Elizabeth J. Mitcham, and Adel A. Kader Department of Pomology, University of California, Davis, CA 95616

Maturity Indices

  • External red color (depending on cultivar)
  • Red color of juice (equal to or darker than Munsell color chart 5R-5/12)
  • Acidity of juice below 1.85%

Quality Indices

  • Freedom from growth cracks, cuts, bruises, and decay
  • Skin color and smoothness
  • Flavor depends on sugar/acid ratio which varies among cultivars. A soluble solids content above 17% is desirable
  • Tannin content below 0.25% is desirable

Optimum Temperature
5°C (41°F) for up to 2 months; longer storage should be at 10°C(50°F) to avoid chilling injury.

Optimum Relative Humidity
90-95%; pomegranates are very susceptible to water loss resulting in shriveling of the skins. Storing fruit in plastic liners and waxing can reduce water loss, especially under conditions of lower relative humidity.

Rates of Respiration

Temperature 5°C(41°F) 10°C(50°F) 20°C(68°F)
ml CO2/kg·hr  2-4 4-8 8-18

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/kg·hr at 10°C (50°F) or lower
Less than 0.2 µl/kg·hr at 20°C (68°F)

Responses to Ethylene
Exposure to ethylene at 1 ppm or higher stimulates respiration and ethylene production rates, but it does not affect their quality attributes. Pomegranates do not ripen after harvest and must be picked fully ripe to ensure the best eating quality.

Responces to Controlled Atmospheres (CA)
Very few studies of the responses of pomegranates to CA have been conducted. Storage in 2% O2 reduces chilling injury if pomegranates are kept below 5°C (41°F). In one study, pomegranates were stored successfully at 6°C (43°F) in 3% O2 + 6% CO2 atmosphere for 6 months.

Physiological Disorders
Chilling Injury. External symptoms include brown discoloration of the skin and increased susceptibility to decay. Internal symptoms include a pale color of the arils (pulp around the seeds) and brown discoloration of the white segments separating the arils. Chilling injury occurs if pomegranates are exposed for longer than one month at temperatures between their freezing point -3 °C (26.6°F) and 5°C (41° F) or longer than two months at 5° C (41 °F).

Pathological Disorders
Heart Rot. This may be caused by Aspergillus spp. and Alternaria spp. Affected fruit show a slightly abnormal skin color, and internally a mass of blackened arils. The disease develops while the fruit is on the tree. Affected pomegranates can be detected and removed by sorters in the packinghouse.

Postharvest Technology Research and Information Center
Department of Pomology
University of California
One Shields Ave., Davis, CA 95616-8683
Send comments and questions to Postharvest Technology Research and Information Center
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Produce/ProduceFacts/Fruit/pomegranate.html updated July 5, 2000

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