- Carrots (Daucus carota) are root vegetables in the Apiaceae family, which also includes celery, parsnip, parsley, dill, caraway, anise, coriander, and fennel.
- In 2012, the U.S. was the 3rd largest producer of carrots. Approximately 80-90% of U.S. carrots are grown in California. Other major producers include Michigan and Texas.
- The introduction of fresh cut and ‘baby carrots’ caused an upsurge in the popularity of carrots in the late 1980s.
- Carrots are high in beta-carotene, Vitamins C and K, potassium, and dietary fiber.
- Carrots are popular as a cooking vegetable, salad item, snack food, and raw vegetable.
- Like most vegetables, carrots are low-acid and therefore at higher risk of contamination with the botulinum toxin, produced by the spore-forming bacterium Clostridium botulinum, when canned improperly. There have been several botulism outbreaks associated with both commercial and homemade carrot juice as well as home-canned carrots.
- Between 1998 and 2017, at least 31 carrot-associated outbreaks were reported to CDC’s National Outbreak Reporting System (NORS), causing 756 illnesses, 17 hospitalizations, and no deaths. In outbreaks with known etiology, the most commonly implicated pathogen was norovirus but have also included Bacillus cereus, Salmonella, sapovirus, Clostridium botulinum, Shigella, and Staphylococcus aureus.
Carrots (scientific name Daucus carota) are root vegetables in the Apiaceae family, which also includes celery, parsnip, parsley, dill, caraway, anise, coriander, and fennel. Domestic carrots originated in Central Asia and wild carrots are indigenous to Europe, North Africa, and Western Asia. Carrots are available in a variety of colors including white, purple, yellow, orange, and red, although orange is the most popular and highest in beta-carotene. Carrots produced in the U.S. are biennial, requiring two full seasons from germination to seed production. However, carrots are commercially grown as an annual and harvested for the large storage root that is produced during the first year. Originally, ‘baby carrots’ were peeled and cut from broken and misshaped larger carrots to reduce waste. However, baby carrots can also be obtained by harvesting carrots before they reach full maturity or by growing miniature strains.
The majority of carrots are sold as fresh cut (including baby) and represent the fastest growing segment of the carrot industry. Carrots are popular as a cooking vegetable, salad item, snack food, and raw vegetable and, in 2015, consumption of carrots was at 8.3 pounds per person in the U.S. Carrots are high in beta-carotene (Vitamin A precursor), and also contain Vitamin C, Vitamin K, potassium, other vitamins and minerals, and dietary fiber.
Foodborne Outbreaks and Recalls
Between 1998 and 2017, at least 31 carrot-associated outbreaks were reported to CDC’s National Outbreak Reporting System (NORS), causing 756 illnesses, 17 hospitalizations, and no deaths. In outbreaks with known etiology, the most commonly implicated pathogen was norovirus (64%), followed by Bacillus cereus (12%), Salmonella (8%), sapovirus (4%), Clostridium botulinum (4%), Shigella (4%), and Staphylococcus aureus (4%).
Below are examples of outbreaks and recalls associated with carrots reflecting the diversity of vehicles, pathogens, and other circumstances:
In 1993, contaminated homemade carrot juice sickened 1 individual (1 hospitalization) with Clostridium botulinum in Washington.
In 1993, contaminated shredded carrots in salads sickened 47 individuals on a Rhode Island flight and 78 individuals at a New Hampshire lodge with enterotoxigenic Escherichia coli O6:NM. The carrots used in the salads, including garden salad and tabbouleh, originated from the same state.
In 2003, contaminated grated carrots sickened 111 individuals with Yersinia pseudotuberculosis O:1 (52%), erythema nodosum (47%), or reactive arthritis (<1%) at daycare centers and schools in Finland. The carrots were included in lunches supplied by a single institutional kitchen. Environmental samples obtained from peeling and washing equipment at the production farm yielded the pathogen.
In 2004, contaminated raw carrots sickened 47 individuals with Shigella sonnei on 12 different flights departing Hawaii and operated by three airlines. All flights provided meals supplied by a single caterer. Cold salads were served on all flights, and raw carrots were the only common salad ingredient. Environmental investigations of the caterer’s facility revealed multiple food hygiene deficiencies. The carrots were obtained from a distributor in Hawaii that had received them from a California vendor.
In 2004, contaminated grated carrots sickened 53 individuals with Yersinia pseudotuberculosis O:1 and erythema nodosum at schools in Finland. The carrots were mixed with white cabbage and included in lunches supplied by the school central kitchen. An environmental sample from the processing plant as well as spoiled carrot and small mammal samples from one of two supplying farms yielded the pathogen.
In 2005, contaminated peeled whole carrots and grated carrots sickened 99 individuals with Cryptosporidium hominis at a company cafeteria in Denmark. The carrots were served at a salad buffet and whole carrots were kept in a bowl of water. An investigation revealed that the water bowl was refilled with carrots twice without changing the water, the water was not necessarily changed every day, and utensils for consumers to take carrots were missing. An ill customer, rather than an ill food worker, was suspected to have been the source of contamination.
In 2006, contaminated home-canned carrots sickened 2 individuals (2 hospitalizations; 0 deaths) with Clostridium botulinum in California.
In 2006, contaminated Bolthouse Farms, Inc. carrot juice sickened 6 individuals (6 hospitalizations; 1 death) with Clostridium botulinum in Georgia, Florida, and Canada. Because the pathogen was only isolated from leftover bottles of juice provided by the cases, improper refrigeration during transport or storage was suspected. Although pasteurized, the juice contained no barriers to bacterial growth, such as combinations of acidity, salt, and sugar content. The implicated products, sold under the brand names Bolthouse Farms, Earthbound Farm, and President’s Choice, were voluntarily recalled.
In 2007, contaminated Los Angeles Salad Company brand baby carrots sickened 4 individuals with Shigella in Canada. The implicated product was distributed to Costco Wholesale retailers throughout Canada as well as other retailers within the U.S. The baby carrots were labeled as a product of Mexico and were voluntarily recalled by Los Angeles Salad Company.
In 2012, Healthy Choice Island Blends, Inc. voluntarily recalled its Liquid Gold brand carrot juice due to potential contamination with Clostridium botulinum. There were no reported illnesses.
In 2012, Bolthouse Farms voluntarily recalled its fresh cut carrot chips due to potential Salmonella contamination. The recall was initiated after routine product sampling yielded the pathogen. The implicated produce items were sold under the brand names Bolthouse Farms, Safeway Farms, and Farm Stand. There were no reported illnesses.
In 2018, Del Monte Fresh Produce prepackaged vegetable trays sickened 250 individuals (8 hospitalization; 0 deaths) with Cyclospora cayetanensis across 4 states. The trays contained carrots, broccoli, cauliflower, celery, and dill dip, and were distributed to multiple retailers. Investigators were unable to identify any individual component of the vegetable trays as the vehicle.
Carrots are most often grown in sandy loam or silt loam soil to promote optimum water holding and drainage. Planting in raised beds can further aid in proper water drainage. Carrots need soil with adequate air and water drainage because wet and compacted soils can cause deformed growth. Soil temperature three inches below the surface should be 50° F or lower. Carrots are a hardy crop that can withstand pH levels ranging from 5.5 to 8.0; however, they tend to thrive best in light, sandy soil with a neutral pH and full sun exposure, as opposed to very clay-like or wet, chalky soil. Before seeding, the soil should be tilled to loosen up compacted ground. For optimum root development and growth, carrots should have approximately 18-24 inches of well-tilled soil that has adequate drainage. The presence of pebbles and stones in the soil can cause forked or misshapen carrots that are unmarketable. Other factors that can cause stubbed or forked roots include pythium root dieback, nematodes, and exposure to frost.
Carrots are a deep-rooting crop that can effectively extract nutrients from the soil. Soil tests should be utilized before planting and throughout crop development to measure soil nutrients such as nitrogen, phosphorous, magnesium, sulfur, boron, manganese, and potassium. If needed, nutrients can be applied prior to seeding and during crop maturation using sidedressing or broadcasting. Carrots are sprinkler irrigated, so most added materials, such as fungicides and fertilizers, are chemigated through sprinkler systems. It is important to be conservative when adding supplemental amounts of nitrogen, as excessive soil nitrogen can result in root cracking during harvest. Adding fresh manure to the soil is not recommended due to food safety concerns and high nitrogen content.
Planting and Irrigation
In nature, carrots are biennial plants that require two growing seasons to complete their life cycle, which culminates in seed production. However, for mature root production, commercial carrots are grown as an annual crop yield. Carrot crops grow optimally in environments with moderately cool days (60-75° F) and colder night (45-50° F). Too high of temperatures can cause bolting, discoloration, and woodiness, making the carrot yield less marketable. Carrots are always direct seeded and can be planted in both the spring and summer. The pounds-per-acre seeding rate varies between raw and coated seeds. High-density seedings are often utilized in carrot production. One potential benefit of high-density seeding is an overall higher yield. However, the decrease in airflow and soil space can negatively impact the size of the carrots and increase the risk of crop disease. The planting density of carrots is dependent on the crop use. Fresh market carrots are planted at 900,000 seeds per acre, whereas baby carrots are planted at 1.5-1.9 million seeds to an acre. Processing carrots are planted at a fraction of that seed density. The ideal seeding depth is 1/8″ – 1/4″ but should not exceed 1/2″.
Maintaining soil moisture is most critical during germination because the seed is planted at such a shallow depth. Moisture stress can result in a higher percentage of cull carrots that are too twisted, knobby, or bent to process or sell in the fresh market. Moisture stress can also hinder sugar set and negatively affect the overall taste. Although average watering volumes differ across the United States, approximately 24”-30” of water is consumed by the crop during the growing season. Sprinkler systems should be able to deliver at least an inch of water within a couple hours but should be slow enough in delivery to allow for proper absorption and to prevent run-off. Efficient sprinkler systems can also be used to apply fertilizer when necessary. In addition to watering, weeding is crucial to the proper health and development of carrot crops. Weeds not only compete for light, water, soil nutrients, and growth space, they can also harbor insects, pathogens, and diseases that are harmful to carrot crops.
Pests of Concern
Carrots are resistant to pests and diseases that affect other crops. Cavity Spot and nematodes are the main pests of concern. Flea beetles, Aster Yellow Disease, and wireworms can also cause problems but are minor in relation to Cavity Spot and nematodes. Several strategies may be employed to avoid flea beetles, including delaying planting by a few weeks in the spring, tilling the garden in the fall to bring the beetles to the surface, and utilizing homemade sprays made from rubbing alcohol, water, and liquid soap.
To protect against Aster Yellow Disease, weeds need to be controlled, and to avoid wireworms, soil should be tested in the fall, prior to the first frost. Prevention of wireworms is important as no insecticide is currently available to control wireworms once the crop is planted.
Harvesting and Handling
Carrots are ready for harvest anywhere between 85-135 days after planting. The prime harvesting period for processed carrots is from September 15-October 15. The fresh market carrot harvest can occur from late July to September, or late into October. Ideally, carrots should be harvested before reaching full maturity. Commercially grown carrots are harvested mechanically using self-propelled, multi-row harvesters. Carrots have their tops removed in the field and are then loaded into trucks and transported to sheds for washing, grading, sizing, and packing. In commercial operations, chlorine concentrations of 100-200 ppm have been recommended for washing carrots, with subsequent potable water rinsing to remove any excess chlorine before the carrots are packaged or prepared for markets. Many farmers selling locally at farmers’ markets are reluctant to use such high levels of chlorine and may only rinse with tap water.
For commercial holding/storage, carrots should be held at 32°F in 98-100% humidity with good airflow. Carrots held in these conditions can be stored for up to seven months. Proper storage is necessary to reduce the risk of postharvest decay such as gray mold rot, watery soft rot, Rhizopus rot, bacterial soft rot, and sour rot. Carrots can be stored with a variety of vegetable products; however, they should not be stored with crops that produce ethylene (i.e., bananas, apples, melons, peaches, and other fruits). Carrot sizing and grading determine whether carrots are sold in fresh market, for processing, or as culls.
Food safety for carrot crops along the farm-to-fork continuum is extremely important, especially given that a large portion of carrots is consumed raw. The University of Georgia Extension, Commercial Production and Management of Carrots, notes that “carrot quality and safety are often perceived by consumers to mean the same thing.” Although high-quality carrots might have good taste and physical appearance, potential pathogens and toxins on the surface of the vegetable can go unnoticed. Fresh vegetables, such as carrots, can serve as vehicles for pathogens that cause foodborne illness, including Salmonella, Shiga-toxin producing Escherichia coli, Shigella, hepatitis A virus, norovirus, Cyclospora cayetanensis, and others. Human infection occurs via the fecal-oral route and there are many points along the farm-to-fork continuum at which broccoli can become contaminated with human or animal feces, either directly or indirectly. There are a variety of potential points for contamination throughout carrot production. Some of these include:
- Land use history — growing carrot crops on or near land where animals have previously grazed can result in pathogenic bacteria in the soil being transferred to the crop.
- Fertilizer use — fertilizers that have been composted improperly can contain pathogenic bacteria.
- Irrigation — when using natural surface water from ponds, lakes, etc., it is possible for the water source to be contaminated and harbor pathogenic bacteria.
- Hand harvesting — harvesting by hand can increase the risk of transferring fecal and bacterial contamination from field workers to the crop.
- Field containers — containers used to hold carrots after harvesting should be non-toxic, free of dangerous materials (wood, nails, splinters, etc.), and able to be cleaned and sanitized to ensure removal of potential contaminants; containers can be sanitized using a strong sodium hypochlorite solution applied from a high-pressure sprayer.
- Pesticide use — the use of illegal pesticides or improper application of pesticides can cause harmful residue contamination on the crop.
Consumers should follow the standard “clean, separate, cook, and chill” food safety practices when preparing carrots. Carrots should be refrigerated (40°F or below) and washed with clean, cold water before consuming. If carrots will be consumed with the skin (i.e. not peeled), they should be cleaned with a vegetable brush. Because carrots are a low-acid food, a pressure canner should be used when home-canning. Pressure canners can heat foods to high temperatures (240-250°F) and therefore destroy any Clostridium botulinum spores potentially present on the surface of the carrots. When home-canning, it is also crucial to follow recommended processing times and pressure levels.
In 2015, Americans consumed an average of 8.3 pounds of fresh carrots per person. In the 2006-2007 Population Survey Atlas of Exposures, 52.4% of the survey cohort reported eating mini-carrots from a sealed bag within the past seven days. In contrast, only 29.9% of the survey cohort reported consuming full size loose or bagged carrots within the past seven days.
Reports by the USDA Economic Research Service have noted different carrot consumption patterns across regions in the United States. In the West, Central, and Eastern regions of the United States, they did not find significant differences between fresh, at-home carrot consumption. However, in the Southern region they found that consumers, on average, ate two pounds less than consumers in the other three regions. Furthermore, the 1998-2003 ACNielsen panel data showed that Non-Hispanic Whites and Asians had the highest at-home carrot consumption. Due to changes and growth in the population, updates to the ACNielsen panel data would be beneficial to represent current demographics and consumer trends in the United States.
For more information on the shelf life of carrots, please visit the FoodKeeper App.
Carrots are a versatile vegetable, readily available fresh, frozen, or canned. The pigmentation of a carrot is due to beta-carotene, the provitamin form of Vitamin A. In selecting for brighter color, the Vitamin A content of common carrot varieties has increased over time. When ingested, beta-carotene is converted to the active form of Vitamin A, which is then bioavailable. Vitamin A is important for immune system functioning and healthy cell growth. Carrots are one of the richest sources of Vitamin A and an excellent source of antioxidants. Carrots are fat free, low in sodium, cholesterol free, a good source of Vitamin C, and low in calories.
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Externally Reviewed by: Joe Nunez, MS Affiliation: UC Cooperative Extension Farm Advisor Reviewed on: 28 August 2015 Externally Reviewed by: Mike Bartolo, PhD Affiliation: CSU Department of Horticulture and Landscape Architecture, Vegetable Crop Senior Research Scientist and Extension Specialist Reviewed on: 3 November 2015