Bilayer edible films with tunable humidity regulating property for inhibiting browning of Agaricus bisporus

Bilayer edible films were fabricated with the stacking double layers, in which the outer and inner layer was consisted of hydrophobic ethyl cellulose and hydrophilic carboxymethyl chitosan hydrogel, respectively. Humidity regulating performance of the films varied with the change of substitution degree of carboxymethyl chitosan. The mechanical properties, water insolubility, water vapor permeability, water contact angle, moisture absorption/desorption characteristics and micro morphology of the film were characterized, which showed that the film can adjust the relative humidity and block the external moisture. The film prepared by carboxymethyl chitosan with the substitution degree of 120% was then selected for the packaging of fresh mushrooms (Agaricus bisporus). The browning of the mushrooms during storage was delayed, as well as the qualities were maintained well, Additionally, the activities and corresponding gene expression of PPO enzyme were inhibited, however for PAL enzyme, an increase was observed.