Fruit Produce Facts English

Pomegranate

Recommendations for Maintaining Postharvest Quality

Carlos H. Crisosto, Elizabeth J. Mitcham, and Adel A. Kader
Department of Plant Sciences, University of California, Davis

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Pomegranate PDF

Maturity & Quality

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

Maturity & Quality Photos

Title: Minimum Maturity Color

Photo Credit: CDFA

Temperature & Controlled Atmosphere

Optimum Temperature

5°C (41°F) for up to 2 months; longer storage should be at 7.2°C (45°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.

Responses 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. In another study a combination of 5% O₂ + 15% CO₂ was found to be effective in decay control and scald prevention for up to 5 months at 7°C (45°F).

Temperature & Controlled Atmosphere Photos

Title: CA Effects (1)

Photo Credit: Don Edwards, UC Davis

Title: CA Effects (2)

Photo Credit: Don Edwards, UC Davis

Disorders

Physiological and Physical 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).

Husk Scald. Brown discoloration of the husk (without any internal symptoms on the arils or surrounding tissues) that occurs during storage for more than 3 months at 7°C (45°F) or lower temperatures.

Pathological Disorders

Gray mold. Caused by Botrytis cinerea, gray mold is the most important postharvest decay-causing fungus. Infection commonly begins in the orchard with spores of the fungus germinating and colonizing senescing blossom tissues in the calyx area. After harvest, the fungus grows into the pomegranate’s rind which turns light brown, tough, and leathery. This is followed by the appearance of gray mycelial growth at advanced stages of fruit decay. Minimizing physical damage of the calyx (crown) and fruit during harvest and postharvest handling, plus maintaining optimal temperature and relative humidity throughout postharvest handling of pomegranates are very important decay control strategies. Sanitation washes of fruit, however, may activate established infections in blossom tissues. Use of fludioxonil (Scholar) as a postharvest fungicide dip or drench is effective in controlling this fungus and is approved by USEPA with a maximum residue limit of 5 ppm. Carbon dioxide enriched atmospheres are fungistatic and cold temperatures also inhibit growth of Botrytis cinerea.

Heart Rot. This may be caused by Aspergillus spp., Alternaria alternata, and Alternaria arborescens. 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.

Disorders Photos

Title: Gray Mold

Photo Credit: Adel Kader, UC Davis

Title: Heart Rot

Photo Credit: Don Edwards, UC Davis

Title: Scald (1)

Photo Credit: Bruno Defelippi, UC Davis

Title: Chilling Injury (1)

Photo Credit: Don Edwards, UC Davis

Title: Chilling Injury (2)

Photo Credit: Don Edwards, UC Davis

Title: Sunburn

Photo Credit: Don Edwards, UC Davis

Title: Scald (2)

Photo Credit: Bruno Defelippi, UC Davis

Date

February 1996

Use of Materials

The UC Postharvest Technology Center grants users permission to download textual pages (including PDF files) from this World Wide Web site for personal use or to reproduce them for educational purposes, but credit lines and copyright notices within the pages must not be removed or modified.

Except for these specified uses, no part of the textual materials available on the UC Postharvest Technology Center Web site may be copied, downloaded, stored in a retrieval system, further transmitted or otherwise reproduced, stored, disseminated, transferred or used, in any form or by any means, except as permitted herein or with the University of California's prior written agreement. Request permission from UC Postharvest Technology Center. Distribution for commercial purposes is prohibited.

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.

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

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