Eco-friendly and intelligent cellulosic fibers-based packaging system for real-time visual detection of food freshness

Intelligent packaging system for real-time visual monitoring the freshness of foods plays a key role in the field of food safety. Employing biopolymer as matrix and natural anthocyanin as pH sensing indicator has arouse growing interest for freshness detecting in recent years. However, the anthocyanin migration phenomenon and relatively poor mechanical strength of film restricted the practicability of biopolymer-based smart packaging system. In this work, we constructed a sort of pH/moisture sensitive chitosan (CS)/carboxymethyl cellulose (CMC) coacervates containing anthocyanin (cyanidin cation type, extracted from blueberry) on cellulosic paper by facile layer-by-layer assembly, in which anthocyanin was firmly anchored. The accumulated release amount of anthocyanin in distilled water was reduced from 78.14% to 19.42% compared to pristine CMC-Anth paper. The maximum tensile strength was significantly improved from 9.51 MPa for initial filter paper to 55.68 MPa for (CS/CMC-Anth)4 colorimetric paper and the compact CS/CMC-Anth bilayer endowed colorimetric paper with excellent structural stability upon folding at least 1000 times. The assembled (CS/CMC-Anth)4 colorimetric paper delivered response to pH/moisture and can be employed to real-time monitor the freshness of pork and fruits. The integration of intelligent sensor technology and food science will make the food industry present a green, efficient, intelligent, accurate and diversified business model in the future.