An intelligent fluorescence platform based on lignocellulose components and fluorescein for food freshness monitoring

In this paper, lignocellulose components were separated under mild conditions to achieve hierarchical utilization of biomass. Cellulose was retained in cellulose pulp with highly crystalline structure, and lignin powder was recovered, which offered a possibility for the high-value utilization of lignocellulosic biomass. The extracted lignin (EL) was carbonized and activated to prepare lignin-based porous carbon microspheres (LPCMs) and further used as a substrate to interact with fluorescein-5-isothiocyanate (5-FITC) for the detection of biogenic amines (BAs). The fluorescence of 5-FITC was found to be quenched in the presence of LPCMs. And then, upon addition of BAs, 5-FITC was released from the surface of LPCMs, which resulted in the fluorescence recovery of 5-FITC. Thus, a novel “turn off–on” fluorescent probe was constructed for sensitive and visual detection of BAs. Meanwhile, the retained cellulose skeleton structure was used to prepare a smart identification label for real-time and visual evaluation of the freshness of pork and shrimp. This work realized the improvement of comprehensive utilization rate of lignocellulose and developed a rapid, efficient, and sustainable method which combined natural lignocellulose materials with green analytical technology for visually evaluating food quality.