Accumulation of Lignin and Malondialdehyde in Relation to Quality Changes of Button Mushrooms (Agaricus bisporus) Stored in Modified Atmosphere

Whole fresh button mushrooms (Agaricus bisporus) were stored in unsealed bags in two types of modified atmosphere packaging (MAP), namely, active and passive, at 4 degrees C. The packaging film was 0.04mm low-density polyethylene and the gas composition of the active MAP was 12% O-2, 2.5% CO2 and 85.5% N-2. Firmness of Mushroom showed a positive correlation with the accumulation of lignin in the tissue. On the other hand, changes of malondialdehyde content with storage time were proportional to the evolution of browning. The button mushrooms in control treatment developed severe browning at the end of the 15-day storage, while the mushrooms of both active and passive MAP treatments browned slightly. MAP treatments could not inhibit phenylalanine ammonia lyase activity; however, it can reduce the lignification process by the inhibition of peroxidase (POD) activity and the accumulation of lignin. Correlation between the cinnamyl alcohol dehydrogenase activity and lignin accumulation was not obvious. Our results suggested that an increase in the firmness of mushrooms during senescence may be a consequence of tissue lignification, a process associated with increase in POD activity. Both active and passive MAPs were useful for the conservation of tenderness and whiteness in button mushrooms.