Xanthan gum ink based on Lycium ruthenicum anthocyanin as an indicator of color change for monitoring freshness of cold fresh meat

The continuous development of intelligent food packaging has led to an increased focus on using freshnessindicating inks, which could provide a high level of quality control and consumer experience. This study aimed to further promote the application of xanthan gum ink in food freshness indication by optimizing its performance in screen printing. A novel freshness-indicating ink was prepared using Lycium ruthenicum anthocyanin (LRA) as the core indicator, glucose as the pigment carrier, soybean oil as the linker, and xanthan gum (XG) as the thickener. Scanning electron microscopy (SEM) demonstrated that the ink was uniformly distributed on paper using screen printing. Rheological and particle size analyses revealed that the incorporation of XG significantly enhanced the interaction force between droplets in the ink system. Further tests on viscosity, fineness, and initial dryness indicated that XG, a natural microbial polysaccharide with excellent stability, could effectively improve the flowability of the ink. Specifically, at a 0.3 % XG content, the ink exhibited a unimodal particle size distribution with an average particle size of 851.02 nm and a zeta potential of -27 mV. This indicated the ink system was stable and uniform, with optimal rheological properties and printing suitability. Furthermore, the printed freshness indication labels exhibited a significant change in color as the freshness of the refrigerated meat changed. This study develops a natural and safe method for monitoring the freshness of refrigerated meat and provides an optimized idea for applying indicator inks.