MATURITY & QUALITY
Maturity Indices
Asparagus spears are harvested as they emerge through the soil from the underground crowns. Typically, spears are cut when they reach approximately 23cm (9 in.). Stalk diameter is not a good indicator of proper maturity and associated tenderness. (See Quality Indices)
Quality Indices
Quality, fresh asparagus will be dark green and firm with tightly closed, compact tips. Stalks are straight, tender and glossy in appearance.
TEMPERATURE & CONTROLLED ATMOSPHERE (CA)
Optimum Temperature
0°-2°C (32°-35.6°F)
Storage life
Typically 14-21 days at 2°C and can be extended up to 31 days by 7-10 days storage at 0°C and atmospheric modification. Extended storage (~10-12 days) in air at 0°C may cause chilling injury.
Optimum Relative Humidity
95-100%; High relative humidity is essential to prevent dessication and loss of glossiness. Drying of the butt-end of spears is a negative quality factor. Commonly asparagus is packed and shipped in cartons with a water-saturated pad to maintain high humidity.
Rates of Respiration
| Temp. °C (°F) |
ml CO2/kg·hr |
| 0 (32) | 14-40 |
| 5 (41) | 28-68 |
| 10 (50) | 45-152 |
| 15 (59) | 80-168 |
| 20 (68 | 138-250 |
| 25 (77) | 250-30 |
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
< 0.1µl/kg·hr at 20°C (68°F)
Responses to Ethylene
Exposure to ethylene will accelerate the lignification (toughening) of asparagus spears in controlled studies. The concentration and duration of exposure to exogenous ethylene, to cause this effect, at commonly encountered levels during storage and distribution are not available.
Responses to Controlled Atmospheres(CA)
Elevated CO2 at 5-10% (typically 7%) in air is beneficial in preventing decay and reducing the rate of toughening of the spears. The beneficial effect is most pronounced if temperatures cannot be maintained below 5°C (41°F). Short (CA) exposure to higher CO2 concentrations (12-20%) is safe and beneficial only if temperatures can be maintained at 0° – 1°C (32° – 33.8°F).
Signs of CO2 injury are small to elongated pits, generally first observed just below the tips. Severe injury results in ribbiness.
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