Preservation and bleaching of sliced mushrooms with hydrogen peroxide According to the article Extending the Shelf Life of Fresh Sliced Mushrooms, it states that 5% (v/v) hydrogen peroxide is an effective means for the preservation of sliced mushrooms.

In regards to the preservation:


  In the USA hydrogen peroxide
  is an approved bactericide for some dairy products and is used for disinfecting fruit
  and vegetables. Its activity is due to its oxidising effects on
  bacteria and it also bleaches mushrooms during the soaking period.


How does oxidising effects cause the bleaching, hence preservation of sliced mushrooms?
Hydrogen peroxide is quite a strong oxidizer. First, let's address the bleaching effect: It bleaches by oxidizing colored compounds, making them colorless. From Wikipedia:


  An oxidizing bleach works by breaking the chemical bonds that make up the chromophore. This changes the molecule into a different substance that either does not contain a chromophore, or contains a chromophore that does not absorb visible light. This is the mechanism of bleaches based on chlorine.


This is also the mechanism of hydrogen peroxide as a bleach, since both chlorine-based bleach and hydrogen peroxide are oxidizers.

As for the antibacterial effect: hydrogen peroxide in this particular concentration (5%) may or may not be effective against bacteria (and viruses, fungi, etc.) due to the presence of the enzyme catalase in some bacteria and fungi. In those organisms which it is effective against, hydrogen peroxide would probably work by causing oxidative stress in the organism.