Preparation and characterization of water vapor-responsive methylcellulose-polyethylene glycol-400 composite membranes and an indication of freshness of shiitake mushrooms.

Intelligent packaging with freshness indication capability can help consumers purchase fresh food. However, current research primarily focuses on carbon dioxide-sensitive intelligent packaging, with limited research on water vapor-sensitive indication packaging. In this study, the water vapor-sensitive indicator membrane was prepared and used to determine the freshness of mushrooms. The results of this study showed that the water permeability of the indicator membrane decreased from 33.17 % to 21.59 % with the increase of Polyethylene glycol-400(PEG-400) content in methylcellulose(MC) membrane, and the contact angle of the indicator membrane increased from 87 % to 98 % with the addition of PEG-400. The addition of plasticizer PEG-400 increased the hydrophobicity of the indicator film, which could be attributed to the improvement of the molecular arrangement and crystallinity of the indicator film by the addition of PEG-400. After encountering water, the transparency of the indicator membrane changes from completely opaque (white) to transparent. Addition of PEG-400 reduces the rate of change in the transparency of the indicator membrane. The indicator membrane was successfully used to indicate the freshness of mushrooms and effectively reflected the freshness of mushrooms during storage. This technology could be applied to measure the freshness of other foods.