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Cabbage

General Information

Round hard cabbages and Chinese (also called Napa) cabbages are from the same genus (Brassica) but different species (B. oleracea var capitata = cabbage, B. campestris var. pekinensis = Chinese cabbage). Chinese cabbages may be cylindrical or rounded and may be less compact than round cabbages. Information mentioned here applies to both types unless stated otherwise.

Maturity Indices

Maturity is based on head compactness. A compact head can be only slightly compressed with moderate hand pressure. A very loose head is immature, and a very firm or hard head is mature.

Quality Indices

After trimming outer wrapper leaves, cabbage heads should be a color typical of the cultivar (green, red, or pale yellow-green), firm, heavy for the size and free of insect, decay, seed stalk development and other defects. Leaves should be crisp and turgid. For round cabbages, grades are U.S. no. 1 and U.S. commercial.

Optimum Temperature and Relative Humidity

Most cabbage is room cooled. Storage at 0°C (32°F) with >95% RH is required to optimize cabbage storage life. Early crop round cabbage can be stored 3-6 weeks, while late crop cultivars can be stored for up to 6 months. For the latter, storage at -0.5°C (31°F) is sometimes recommended. Chinese cabbage can be stored from 2 to 6 months, depending on cultivar, at 0° to 2.5°C (32° to 36°F). Deterioration of cabbage during storage is associated with stem or seed stalk growth (bolting), root growth, internal breakdown, leaf abscission, discoloration, decay and black speck. Long-term storage usually results in extensive trimming of heads to remove deteriorated leaves.

Freezing Injury

Freeze damage appears as darkened translucent or water-soaked areas that will deteriorate rapidly after thawing. Freeze damage can occur if round cabbages are stored below -0.9°C (30.4°F) and if Chinese cabbage is stored below -0.6°C (31°F).

Rates of Respiration

Round and Chinese cabbages have similar moderately low respiration rates:

Temperature

0°C (32°F)

5°C (41°F)

10°C (50°F)

15°C (59°F)

20°C (68°F)

ml CO2/kg·hr

2 – 3

4 – 6

8 – 10

10 – 16

14 – 25

Respiration rates of shredded cabbage are 13-20 mL CO2/kg·hr at 5°C (41°F).

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.

Rates of Ethylene Production

Ethylene production rates are generally very low: <0.1 µL/kg·hr at 20°C (68°F), although higher rates have been reported for Chinese cabbage.

Responses to Ethylene

Cabbages are sensitive to ethylene, which causes leaf abscission and leaf yellowing. Adequate ventilation during storage is important to maintain very low ethylene levels. Ethylene does not increase the disorder “black speck” or “pepper spot”.

Responses to Controlled Atmospheres (CA)

Some benefit to shelf-life can be obtained with low O2 (2.5-5%) and high CO2 (2.5-6%) atmospheres at temperatures of 0-5°C (32-41°F). CA storage will maintain color and flavor of cabbage, retard root and stem growth, and reduce leaf abscission. O2atmospheres below 2.5% for round cabbage and 1% for Chinese cabbage will cause fermentation, and CO2 atmospheres >10% will cause internal discoloration.

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