carrots

Scientific Name and Introduction: Carrots (Daucus carata L.) are biannuals of the Apiaceae
(Umbelliferae) family. The edible portion is the storage taproot, which contains high levels of
carbohydrates (sugars) and ß-carotene (pre-vitamin A). Most of the carrots in U.S. markets are produced in
California complemented by limited production in Michigan, Texas, Colorado, Florida and Washington
(Schaffer, 2000), and are available year round.
Quality Characteristics and Criteria: Quality criteria vary with the end usage. In general, high quality
carrots are firm, straight from “shoulder” to “tip,” smooth with little residual “hairiness,” sweet with no
bitter or harsh taste, and show no signs of cracking or sprouting (Suslow and Cantwell, 1998).
Horticultural Maturity Indices: Harvest maturity varies with the market outlet and the end usage. For
fresh market, most carrots are harvested partially mature, when the roots are about 1.8 cm (0.75 in) or larger
in diameter at the upper end (Kotecha et al., 1998). Late harvesting may improve storability by reducing
decay during extended storage (Suojara, 1999). For fresh-cut processing, carrots are harvested immature to
insure they are tender and sweet.
Grades, Sizes and Packaging: Carrots can be harvested either bunched or top trimmed; top trimmed is the
dominant method. The common grades for bunched carrots are No. 1 and commercial grade. For topped
carrots, the grades are extra No. 1, U.S. No. 1, No. 1 Jumbo, and No. 2. Topped carrots are typically packed
in 0.5 to 2.25 kg (1 to 5 lb) consumer bags that are grouped in 11 or 22 to 22.7 kg (24 or 48 to 50 lb) cartons
or master poly bags. Bunched carrots are packed loosely in 12 kg (26 lb) cartons.
Pre-cooling conditions: Prompt washing and hydro-cooling to < 5 °C (41 °F) is essential to maintain carrot freshness and crispness. Typically, carrots pass through several wash and flume steps that remove field heat and are then hydrocooled in chlorinated water before packing. Optimum Storage Conditions: Storage temperature at 0 to 1 °C (32 to 33.8 °F) is essential to minimize decay and sprouting during storage. High RH is required to prevent desiccation and loss of crispness. The recommended conditions for commercial storage are 0 °C (32 °F) with 98 to 100% RH. Under this condition, mature topped carrots can be stored for 7 to 9 mo. However, commercial storage and distribution condition rarely achieve the optimum storage conditions and topped carrots can be stored for 5 to 6 mo at 0 °C (32 °F) to 5 °C (41 °F) with 90 to 95% RH. Common “Cello-pack” carrots are typically immature and may be stored successfully for 2 to 3 weeks at 3 to 5 °C (37.4 to 41 °F). Bunched carrots are highly perishable due to the presence of leaves and can be maintained for only 8 to 12 days. Bunched carrots are typically shipped and stored with shaved or flake-ice. Controlled Atmosphere (CA) Considerations: CA generally does not extend storage-life of carrots beyond that in air with high RH (Leshuk and Saltveit, 1990). Low O2 (1%) inhibited sprouting, but also promoted decay (Abdel-Rahman and Isenberg, 1974). CO2 injury appears as soft brown spots upon exposure to air. CO2 levels > 5% promote decay. Storage at < 3% O2 can result in increased bacterial rot,
off-flavors, and off-odors (Leshuk and Saltveit, 1990).

Retail Outlet Display Considerations: Carrots are often displayed loosely on a shelf with mist or in
polyethylene consumer packages.
Chilling Sensitivity: Carrots are not chilling sensitive and should be stored as cold as possible without
freezing. Their freezing point is -1.2 °C (29.8 °F).
Ethylene Production and Sensitivity: Carrots produce very low ethylene at < 0.1 µL kg-1 h-1 at 20 °C (68
°F). Exposure to exogenous ethylene (~ 0.2 µL L-1) will induce development of isocoumarin and bitter
flavor (Lafuente et al., 1996; Talcott and Howard, 1999). Induction and accumulation of isocoumarins is
greatest on cut but not yet peeled carrot sections. Exposure of peeled carrot to ethylene does not result in
development of bitterness. Thus, whole or sectioned carrots should not be mixed in storage with
ethylene-producing commodities.