A novel colorimetry-enhanced and UV-blocking intelligent pH indicator by incorporation of lignin nanoparticle for monitoring shrimp freshness

The current anthocyanin-based intelligent pH indicator has poor ultraviolet (UV) blocking performance, which results in color fading and greatly limits its application in freshness monitoring. Lignin nanoparticle (LNP), with aromatic skeleton and phenolic hydroxyl groups, is a promising green alternative to reinforce UV shielding property. Herein, a colorimetry-enhanced and UV-blocking intelligent film encapsulating purple sweet potato anthocyanin (PSPA) and LNP was developed by electrospinning poly (vinyl alcohol) (PVA) and zein. The results revealed that a bead-free and continuous microstructure was obtained for the PVA/Zein/PSPA/LNP-2 film, which also achieved excellent 99.99 % UVA and UVB blocking. Light exposure experiments showed that the incorporation of LNP significantly improved the color stability of PSPA. Besides, the film demonstrated higher tensile strength (26.98 MPa) and elongation at breaks (66.06 %). Furthermore, the nanofiber structure endowed the film with sensitive color responsiveness to detect shrimp freshness with color changing from pink to blue. These results suggested the great potential of developed nanofilm as an intelligent indicator.