Smart colorimetric sensing films with high mechanical strength and hydrophobic properties for visual monitoring of shrimp and pork freshness

During recent years the use of smart colorimetric packaging films for monitoring food freshness has received widespread attention. However, their poor mechanical strength and hydrophilic properties are the major problems hindering the large-scale application. Here, we employed biodegradable cellulose and naphthoquinone dyes extracted from Arnebia euchroma (AENDs) to fabricate a novel colorimetric sensing film with high tensile strength of 227 MPa and hydrophobic properties (water contact angle of 112.2°) for real-time monitoring of the freshness of shrimp and pork. In addition, the effectiveness of the sensing film in detecting the freshness of shrimp and pork under 20 °C, 4 °C and-20 °C conditions was confirmed by measuring the total volatile basic nitrogen (TVBN) and total viable count (TVC). Visual observation confirmed that the sensing film clearly changed from rose-red to purple, then to bluish violet providing a good indication of spoilage, which correlated well with TVBN and TVC content in shrimp and pork measures by standard lab procedures. The colorimetric sensing film developed here would be promising in fabricating high mechanical strength and hydrophobic properties smart labels for visual monitoring the freshness of shrimp and pork.