Fresh cultivated mushroom shelf life comes down to temperature, humidity and bruising. According to USDA Agriculture Handbook 66, mushrooms cooled quickly and held at 0-1 °C with 95% relative humidity keep for 7-9 days; at 2 °C surface browning, stem elongation and veil opening speed up and storage life falls to 3-5 days.
- Temperature: mushrooms are pre-cooled to 2-4 °C straight after harvest and kept below 4 °C on the retail shelf. At 20 °C they respire roughly seven times faster than at 0 °C, and below -0.6 °C they freeze, leaving caps water-soaked and very soft.
- Humidity: a mushroom that dries out loses its gloss, its stem blackens and its veil opens. A perforated polyethylene overwrap holds moisture in, but there must be no condensation inside the pack.
- Bruising: rough handling turns the tissue brown, and a bumpy road, a tight stack or an over-deep crate all do the same.
- Neighbours: ethylene browns the caps and mushrooms absorb the smell of green onions, so they are kept apart from both.