the storage period. On the other hand, the firmness of mushrooms packaged in MAP3 was the highest within three groups during the first 7 d of storage, while it became the lowest at the later storage. But, no significant differences were found in the firmness of mushrooms packaged in these three conditions. CO2 concentrations higher than 12% cause loss of firmness and an increase in the enzymatic browning of Agaricus mushrooms due to cell membrane damage. With the extension of storage time, the O2 concentrations decrease while the CO2 concentrations increase (Jiang 2010). The CO2 concentration in the packages of MAP3 treatment was the highest, which could answer why the MAP3 treatment showed the lowest firmness than the other two groups.