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Grapefruit

Recommendations for Maintaining Postharvest Quality

Mary Lu Arpaia¹ and Adel A. Kader²

¹Dept. of Botany and Plant Sciences, Univ. of California, Riverside

²Department of Plant Sciences, University of California, Davis

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Maturity & Quality

Maturity Indices

Color (more than 2/3 of fruit surface showing yellow color) and a minimum soluble solids/acid ratio of 5,5 or 6 (depending on production area). Grapefruit do not continue to ripen after harvest so they should be harvested fully-ripe (with good flavor).

Quality Indices

Color intensity and uniformity
Firmness
Size
Shape
Peel thickness; smoothness
Freedom from decay and defects, such as freezing injury, rind staining, pitting, scars, and insect damage
Flavor is related to soluble solids/acid ratio and concentration of compounds that impart bitter flavor (limonin and naringin)

Temperature & Controlled Atmosphere

Optimum Temperature

12-14°C (54-57°F) depending on cultivar, production area, maturity-ripeness stage at harvest, and storage and transport duration (up to 6-8 weeks).

Optimum Relative Humidity

90-95%

Rates of Respiration

Temperature	10°C (50°F)	13°C (55°F)	15°C (59°F)	20°C (68°F)
ml CO₂/kg·hr	3-5	4-7	5-9	7-12

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 20°C (68°F)

Responses to Ethylene

Exposure of mature-green grapefruits for 1-3 days to ethylene (1-10ppm) at 20-30°C (68 to 86°F) accelerates loss of green color and appearance of yellow color (degreening). This is accompanied by faster peel senescence and greater susceptibility to decay-causing pathogens.

Responses to Controlled Atmospheres (CA)

Low O₂ (3-10%) and high CO₂ (5-10%) concentrations delay senesence and maintain firmness of grapefruits kept at 13-15°C (55-59°F)
Exposure to O₂ levels below 3% and/or CO₂ levels above 10% may result in off-flavors due to accumulation of acetaldehyde, ethanol, and ethyl acetate. This precludes the use of fungistatic levels of CO₂ (>10%) for longer than a few days
Commercial use of CA during transport and/or storage of grapefruits is very limited

Temperature & Controlled Atmosphere Photos

Title: Chilling Injury (1)

Photo Credit: Bill Grierson, University of Florida

Title: Chilling Injury (2)

Photo Credit: Don Edwards, UC Davis

Disorders

Physiological and Physical Disorders

Chilling injury. Severity of chilling injury depends upon cultivar, maturity and ripeness stage at harvest, production area and season (preharvest cultural practices and weather conditions). Symptoms including pitting, reddish brown discoloration, scald, watery breakdown, off-flavors, and increased decay incidence. Waxing or film wrapping to minimize water loss and use of fungicides (especially thiabendazole) to control decay can reduce severity of chilling injury symptoms. Conditioning at 15-18°C (59-65°F) in air or in air + 10-20% CO₂ for 5-7 days can reduce severity of chilling injury symptoms on grapefruits that are subsequently exposed to chilling temperatures, such as those required for quarantine treatments against tropical fruit flies.

Oil spotting (Oleocellosis). Physical stress on turgid fruits may result in breaking of oil cells and release of oil that damages surrounding tissues.

Pathological Disorders

Important Diseases:

Green mold (Penicillium digitatum)
Blue mold (Penicillium italicum)
Phomopsis stem-end rot (Phomopsis citri)
Stem end rot (Lasiodiplodia theobromae)
Brown rot (Phytophthora citrophthora)
Sour rot (Geotrichum candidum)

Control Strategies

Careful handling to minimize physical damage
Good sanitation in the orchards and packing houses
Treatment with hot water dip (50-53°C [120-125°F] for 2-3 minutes) or drench (55°C [129°F] for 20-30 seconds)
Treatment with postharvest fungicides and/or biological antagonists
Prompt cooling and expedited handling
Removal and/or exclusion of ethylene

Date

May 1999

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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