Total Sulfur Dioxide Residuals in Fresh Mushrooms Washed in Sulfite Solutions 1 .

Freshly-harvested, cultivated mushrooms ( Agaricus bisporus ) were washed in 1000 ppm solutions of sodium sulfite and stored in ventilated, polyvinylchloride film-overwrapped packages at 5 and 15°C. Total sulfur dioxide of the mushrooms was measured by the modified Monier-Williams procedure numerous times during a 48-h storage period. Initial SO ₂ averaged 48.1 ppm and subsequently declined at a logarithmic rate. Total SO ₂ fell below detectable levels (<10 ppm) at about 11.8 and 15.6 h at 15 and 5°C, respectively.