Preparation and properties of nano-SiO₂/anthocyanidin/ regenerated cellulose smart colorimetric sensing film for food freshness monitoring

Smart food packaging can make up for the shortcomings of traditional packaging in real-time quality monitoring, so exploiting a low cost, harmless to human health and green food freshness intelligent indicator label is of great significance for food safety. Therefore, in this study, we employed regenerated cellulose (RC) films, anthocyanidin extracted from red cabbage and nano-SiO₂ to fabricate a biodegradable smart colorimetric sensing film (RCG-PCE-Si). This film has good mechanical properties (maximum stress is 67.1 MPa, and maximum tensile strain is 45.50%) and super-hydrophobicity (water contact angle is 152.8°), and has a certain barrier ability to ultraviolet light, which can be used for real-time monitoring of fresh food freshness. In addition, the effectiveness of the film in detecting the freshness of shrimp was confirmed by measuring the total volatile basic nitrogen (TVBN) and pH value, and its color obviously changes from magenta to water-red, then to grey-purple, and then to grey-green, effectively indicating the spoilage of shrimp. The colorimetric sensing film developed here would be used as an intelligent colorimetric label with good mechanical properties and super-hydrophobicity, and can be applied to intelligent packaging that can monitor the freshness of food in real time.