University of California

Vegetables English

Carrot

Recommendations for Maintaining Postharvest Quality

carrots071
Trevor V. Suslow, Jeffrey Mitchell and Marita Cantwell

Department of Plant Sciences, University of California, Davis

Maturity & Quality

Maturity Indices

  • In practice, harvest decisions for carrots are based on several criteria depending on the market outlet or sales endpoint
  • Typically carrots are harvested at an immature state when the roots have achieved sufficient size to fill in the tip and develop a uniform taper
  • Length may be used as a maturity index for harvest timing of ‘cut and peel' carrots to achieve a desired processing efficiency

Quality Indices

There are many visual and organoleptic properties that differentiate the diverse varieties of carrots for fresh market and minimal processing. In general, carrots should be:

  • Firm (not flacid or limp)
  • Straight with a uniform taper from ‘shoulder' to ‘tip'
  • Bright orange
  • There should be little residual "hairiness" from lateral roots
  • No "green shoulders" or "green core" from exposure to sunlight during the growth phase
  • Low bitterness from terpenoid compounds
  • High moisture content and high reducing sugars are most desireable for fresh consumption

U.S. Grades:

  • Bunched Carrots - No. 1 and Commercial Grade
  • Topped Carrots - Extra No. 1, U.S. No. 1, No. 1 Jumbo, No. 2

Quality Defects include lack of firmness, non-uniform shape, roughness, poor color, splitting or cracking, green core, sunburn, and poor quality of tops or trimming.

Maturity & Quality Photos

carrots_with_tops

Title: Carrots with Tops

Photo Credit: Adel Kader, UC Davis

Temperature & Controlled Atmosphere

Optimum Temperature

0°C (32°F)

Storage life at 0°C is typically:

  • Bunched: 10-14 days
  • Immature roots: 4-6 weeks
  • Mature roots: 7-9 months
  • Fresh-cut (Lightly processed): 3-4 weeks

Common storage conditions rarely achieve the optimum temperature for long- term storage to prevent decay, sprouting, and wilting. At storage temperatures of 3-5°C, mature carrots can be stored with minimal decay for 3-5 months.

Common ‘Cello-pack' carrots are typically immature and may be stored successfully for 2-3 weeks at 3-5°C. Bunched carrots are highly perishable due to the presence of the shoots (tops). Good quality is generally maintained only for 8-12 days, even with contact ice.

Lighlty processed (fresh-cut, cut and peel) carrots typically maintain quality of 2-3 weeks at 3-5°C.

Optimum Relative Humidity

98-100%

High relative humidity is essential to prevent dessication and loss of crispness. Free moisture from the washing process or unevaporated condensation, common with plastic bin-liners (and due to fluctuating temperatures) will promote decay.

Rates of Respiration

Temperature ml CO2/kg·hr
°C (°F) Topped Bunched
0 (32) 5-10 9-18
5 (41) 7-13 13-25
10 (50) 10-21 16-31
15 (59) 13-27 28-53
20 (68) 23-48 44-60
25 (77) NA NA

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.
NA= Not applicable.

Rates of Ethylene Production

>0.1 µl/kg·hr at 20°C (68°F)

Responses to Ethylene

Exposure to ethylene will induce the development of bitter flavor due to isocoumarin formation. Exposure to as little as 0.5ppm exogenous ethylene will result in perceptible bitter flavor, within 2 weeks, at normal storage conditions. Thus, carrots should not be mixed with ethylene-producing commodities.

Responses to Controlled Atmospheres (CA)

Controlled atmosphere is of limited use for carrots and does not extend postharvest life of carrots beyond that in air. CO2 concentrations above 5% have been shown to increase spoilage. Low oxygen concentrations, below 3%, are not well tolerated and generally results in increased bacterial rot.

Disorders

Physiological and Physical Disorders

Intact Roots. Bruising, shatter-cracks and tip-breakage are signs of  rough handling. Nantes-type carrots are particularly susceptible. Sprouting will continue as carrot roots develop new shoots after harvest. This is one reason low temperature postharvest management is critical. Common associated disorders include wilting, shriveling, or rubberiness due to dessication. White Root is a physiologic disorder due to suboptimal production conditions which results in patchy or streaks of low color on the carrot roots.

Intact or Fresh-cut. Bitterness may be caused by preharvest stress (improper irrigation scheduling) or exposure to ethylene from ripening rooms or mixing with commodities such as apples. Freezing injury will likely result at temperatures of -1.2°C ( 29.5°F) or lower. Frozen carrots generally exhibit an outer ring of water-soaked tissue, viewed in cross section, which blackens in 2-3 days.

Fresh-cut. White Blush, due to dehydration of cut or abrasion-peeled surfaces, has been a problem on fresh-cut carrots. Sharp cutting blades and residual free-moisture on the surface of the processed carrots will significantly delay the development of the disorder.

Pathological Disorders

The most prominent postharvest disease concerns are Gray Mold (Botrytis rot) Watery Rot (Sclerotinia rot), Rhizopus rot, Bacterial Soft Rot, induced by Erwinia carotovora subsp. carotovora and Sour Rot (Geotrichum rot). Proper handling and low temperature storage and transportation conditions are the best methods to minimize losses.

Special Considerations

Rapid hydrocooling soon after harvest is strongly recommended.

Disorders Photos

carrots_bacterial_soft_rot2

Title: Bacterial Soft Rot (2)

Photo Credit: Don Edwards, UC Davis 

carrot_BlackMold

Title: Black Mold

Photo Credit: Don Edwards, UC Davis 

carrots_crater_rot

Title: Crater Rot

Photo Credit: Don Edwards, UC Davis 

carrots_gray_mold_rot

Title: Gray Mold Rot

Photo Credit: Don Edwards, UC Davis 

carrots_pitting

Title: Pitting

Photo Credit: Marita Cantwell, UC Davis  

carrots_white_rot

Title: White Rot

Photo Credit: Don Edwards, UC Davis 

carrots_bacterial_soft_rot1

Title: Bacterial Soft Rot (1)

Photo Credit: Marita Cantwell, UC Davis  

Date

June 2002

Use of Materials

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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).

College of Agricultural & Environmental Sciences
Postharvest Technology Center
Department of Plant Sciences

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