An intelligent indicating label using mulberry pigment, polylactic acid and rutile TiO2 nanoparticle for monitoring the freshness of cold fresh pork

The purpose of this work is to develop a new type of intelligent indicating label with high sensitivity to volatile bioamine, anti-ultraviolet light and anti-pigment leakage characteristics by electrospinning for real-time visual monitoring the freshness of cold fresh pork. By investigating pH discoloration sensitivity and light stability of plant pigments with different structures, mulberry pigment was selected as the indicator of indicating label. The content of label components (mulberry pigment, polylactic acid and TiO2 nanoparticle) significantly affected label performance (light stability, responsiveness to trimethylamine, and anti-leakage of mulberry pigment), and the optimal component content was determined to be 6.01% (w/w) of polylactic acid, 0.62% (w/w) of TiO2 nanoparticles and 0.29% (w/w) of mulberry pigment by response surface test based on label performance as response value. A close correlation (the correlation coefficient R values of 0.86–0.97) between the total color difference (ΔE) of the label and the freshness indexes (total plate count, total volatile basic nitrogen content, pH, thiobarbituric acid value and sensory score) of cold fresh pork during cold storage was revealed, and the freshness level of unknown pork samples could be well quantitatively predicted by partial least squares regression models with the determination coefficient (R2) values of 0.89–0.92, facilitating producers, dealers and consumers to know pork quality promptly.