Quality, fresh asparagus will be dark green and firm with tightly closed, compact tips. Stalks are straight, tender and glossy in appearance.
Postharvest storage temperature
Spears should be held at 0°C–2°C. Asparagus will continue to develop after harvest, which is why low temperature postharvest management is critical. Spear toughening occurs rapidly at temperatures above 10°C. Asparagus is sensitive to chilling injury after 10 days at 0°C. Symptoms include loss of sheen or glossiness and greying of the tips. Severe chilling injury may result in darkening near tips in spots or streaks. Freezing injury (water-soaked appearance leading to extreme softening) will likely result at temperatures of -0.6°C or lower.
Controlled atmosphere storage
Elevated CO2 at 5–10% 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. Short exposure to higher CO2 concentrations (12–20%) is beneficial only if temperatures can be maintained at 0°C–1°C. Signs of CO2 injury are small to elongated pits, generally first observed just below the tips.
Exposure to ethylene may accelerate the toughening of asparagus spears.
Store at 95–100% relative humidity. High relative humidity is essential to prevent desiccation 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.
Disease & infection
The most prominent postharvest disease concern is bacterial soft rot, induced by erwinia carotovora subsp. carotovora. Decay may initiate at the tips or the butt end. Spears that are re-cut above the white portion of the butt end are reported to be most susceptible to bacterial decay.
Trim before use. Store in jar of water in fridge with tips covered by plastic bag.
Cook asparagus whole to retain nutrients and chop after cooking if necessary. Cook with minimal water to maintain maximum health benefits.