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. Visible, open gills and absence of a stipe are negative factors. U.S. grades are No. 1 and No. 2.
Grades discriminate for maturity, shape uniformity, cleanliness and trim quality.
Drying is correlated with blackening of the stipe and gills and curling of the cap. Commonly mushrooms are packed and shipped in cartons with a perforated overwrap to maintain high humidity. Responses to Ethylene Agaricus mushrooms are not significantly impacted by exogenous ethylene. Improper control of controlled atmospheres or improper packaging can rapidly lead to depletion of oxygen resulting in conditions favorable for Clostridium botulinum . For this reason, primarily, the use of CA and MA is not common.