Harvesting and Handling
(Button) mushrooms are harvested by maturity and not by size. Maturity is reached when the caps are well- rounded and the partial veil is completely intact. The stipe (stalk) should have a small length to thickness ratio. Stipe length should be sufficient to permit some trimming without cutting flush to the veil.
Good quality, fresh (button) mushrooms should be white to dark brown. White forms are most prevalent. Uniform, well rounded cap with a smooth glossy surface and fully intact veil are indicators of best quality. Stipes are straight and glossy in appearance with an even cut edge. Cleanliness (minimal growth medium residue) and absence of browning or other discoloration are additional quality factors. Visible, open gills and absence of a stipe are negative factors.
Mushrooms should be packed in trays or cartons with a perforated polyethylene film over-wrap to reduce moisture loss. It is important to avoid water condensation inside packages. There are no chemical treatments to extent storage-life of mushrooms intended for fresh consumption. Low storage temperatures are needed to reduce continued development of mushrooms that occurs after harvest. Common disorders include upward bending of caps and opening of the veil. Mushrooms are easily bruised by rough handling and develop brown discoloured tissue.
Cooling and Storage
Mushrooms can be held for 7 to 9 days upon rapid cooling and storage at 0°C to 1°C with 95% RH. Storage at 2°C shortens storage life to 3 to 5 days by accelerating surface browning, stipe elongation, and veil opening. High RH is essential to prevent desiccation and loss of glossiness. Moisture loss is correlated with stipe blackening and veil opening.
Mushrooms produce very low amounts of ethylene. Since ethylene causes browning of mushroom caps, they should be kept separately from ethylene-producing fruits and vegetables.
Controlled atmosphere considerations
Extended storage (~12-15 days) in 3% O2 and 10% CO2 at 0°C has been Controlled demonstrated. Elevated CO2 at 10-15 % (typically 10%) in air is beneficial in Atmosphere (CA) preventing decay and reducing the rate of blackening of the stipe and gills. The beneficial effect is most pronounced if temperatures cannot be maintained below 5°C. Short exposure to higher CO2 concentrations (20 %) is safe and beneficial only if temperatures can be maintained at 0° – 1°C.
Improper control of controlled atmospheres or improper packaging can rapidly lead to depletion of oxygen resulting in conditions favourable for decay. For this reason, primarily, the use of CA and MA is not common. Mushrooms produce very low amounts of ethylene. Since ethylene cause browning of mushroom caps, they should be kept separately from ethylene-producing fruits and vegetables.
Bacteria rots, Chilling injury, Dehydration.