Broccoli

MATURITY & QUALITY

Maturity Indices

Head diameter and compactness; all florets (beads) should be closed.

Quality Indices

Good quality broccoli should have dark or bright green closed florets. The head should be compact (firm to hand pressure), with a cleanly cut stalk of the required length. There should be no yellow florets and there should be no discoloration on the stem bracts.

TEMPERATURE & CONTROLLED ATMOSPHERE (CA)

Optimum Temperature and Relative Humidity

Low temperature is extremely important to achieve adequate shelf-life in broccoli. A temperature of 0°C (32°F) with >95% RH is required to optimize broccoli storage life (21-28 days). Heads stored at 5°C (41°F) can have a storage life of 14 days; storage life at 10°C (50°F) is about 5 days. Broccoli is usually rapidly cooled by liquid-icing the field-packed waxed cartons. Hydrocooling and forced-air cooling also can be used, but temperature management during distribution is more critical than with iced broccoli.

Freezing Injury

Broccoli will freeze if stored at -0.6°C (30.6°F) to -1.0°C (30°F). This may also occur if salt is used in the liquid-ice cooling slurry. Frozen and thawed areas on the florets appear very dark and translucent, may discolor after thawing and are very susceptible to bacterial decay.

Rates of Respiration

Broccoli heads have relatively high respiration rates:

The respiration rates of florets are slightly more than twice the rates of the intact heads.
To calculate heat of 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

Very low, <0.1 µL/kg·h at 20°C (68°F).

Responses to Ethylene

Broccoli is extremely sensitive to exposure to ethylene. Floret yellowing is the most common symptom. Exposure to 2 ppm ethylene at 10°C (50°F) reduces shelf-life by 50%.

Responses to Controlled Atmospheres (CA)

Broccoli can be benefitted by 1-2% O₂ with 5-10% CO₂ atmospheres at a temperature range of 0-5°C (32-41°F). Although under controlled conditions such low O₂ levels extend shelf-life, temperature fluctuations during commercial handling make this risky as broccoli can easily produce offensive sulfur-containing volatiles. As a result, a high rate of air exchange is recommended in standard marine container shipments of broccoli. Most modified atmosphere packaging for broccoli is designed to maintain O₂ at 3-10% and CO₂ at about 7-10% to avoid the development of these undesirable off-odor volatiles.