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Fruit Produce Facts English
Apple, Red Delicious
Recommendations for Maintaining Postharvest Quality
Elizabeth J. Mitcham, Carlos H. Crisosto and Adel A. Kader Department of Plant Sciences, University of California, Davis
Maturity & Quality
Maturity IndicesFirmness of 18 pounds-force, core clear of starch. Firmness (lbs-f) x soluble solids (%) x starch score (1 to 6 scale) should equal 250 at initiation of harvest. Quality Indices
Maturity & Quality Photos
Title: Starch Staining Pattern Photo Credit: Don Edwards, UC Davis
Temperature & Controlled Atmosphere
Optimum Temperature0°C ± 1°C (32°F ± 2°F); Freezing temperature: -1.7°C (29°F) Optimum Relative Humidity90-95% RH Rates of Respiration1
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. 1Higher rates for riper apples. Rates of Ethylene Production2
2Higher rates for riper apples. Responses to EthyleneEthylene stimulates ripening. Mixed results on the benefits of scrubbing ethylene from storage rooms, depending on harvest maturity and type of storage (air or CA). Responses to Controlled Atmospheres (CA)Fruit to be stored longer than 1 month benefit from CA storage in terms of retention of acidity and firmness and reduction of scald incidence and severity. CA storage potential is up to 10 months (vs. 6 months in air). Recommended atmosphere: 1 to 2% O2 + 2 to 4% CO2 Temperature & Controlled Atmosphere Photos
Title: Low O2 Injury Photo Credit: Don Edwards, UC Davis
Disorders
Physiological and Physical DisordersBruising. Can be excessive. Gentle handling is important. Watercore. Can be important later in the harvest season. Water-soaking of the flesh near the core due to an accumulation of sorbitol in the intercellular spaces. Market promptly to avoid internal browning and breakdown. Bitter Pit. Sunken brown spots on the skin, especially at the calyx end, related to low calcium concentration in the apple. Best controlled by calcium sprays prior to harvest and calcium dips prior to cold storage. Reduced incidence with controlled atmosphere storage. Superficial Scald. Browning of the skin which develops in cold storage. High susceptibility. Use diphenylamine at label rates. Controlled atmosphere storage delays onset. Ultra-low oxygen CA storage has been effective in some growing areas. Controlled Atmosphere Damage. Oxygen concentrations below 1% and/or CO2 levels above 10% may induce off-flavor associated with fermentative metabolites. Elevated CO2 injury sypmtoms include partially sunken brown lesions on skin and/or internal browning and cavities. Low O2 injury can result in a purple cast to the skin of Red Delicious apples. Pathological DisordersMoldy Core. Caused by several fungi including Alternaria sp., Fusarium sp., Aspergillus and Penicillium. Red Delicious apples are particularly susceptible because of the open or deep sinus cavity. Drenching can increase the incidence of moldy core. Blue Mold and Grey Mold. The two most important postharvest diseases of Red Delicious apples are caused by Penicillium expansum and Botrytis cinerea. Both fungi are wound pathogens. Sanitation is critical to control of these diseases. Drenching can spread spores of Penicillium and Botrytis to wounds from harvest operations. Use of fungicides during drenching may reduce decay. [For more information, see our publication "Fruit Ripening And Ethylene Management", available for purchase using our Publication order form.] Disorders Photos
Title: Blue Mold Photo Credit: Don Edwards, UC Davis 
Title: Gray Mold Photo Credit: Don Edwards, UC Davis 
Title: Skin cracking Photo Credit: Don Edwards, UC Davis
Date
August 1999 |
Use of Materials
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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.
http://ucanr.edu/sites/Postharvest_Technology_Center_/Commodity_Resources/Fact_Sheets/Datastores/Vegetables_English/?uid=19&ds=799 (Accessed January 18, 2014).
