Carrot

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.

TEMPERATURE & CONTROLLED ATMOSPHERE (CA)

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

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

>0.1µl/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.