A reversible color switching nano-sensing label based on polyvinyl alcohol-acidochromic chitosan (PVA-ACS) for enhanced recognition of meat freshness

In this work, an intelligent and sensitive polyvinyl alcohol-acidochromic chitosan (PVA-ACS) nano-sensing label was developed for visually monitoring meat freshness. Based on the synthesis of 1-hydroxy-4-[4-(ethylsulfurate sulfonyl)-phenylazo]-naphthalene (HESPN), ACS was prepared through hydrogen bonding between the sulfonic acid groups in HESPN structure and the hydroxyl groups in chitosan (CS). Herein, PVA was used as the functional matrix and electrospinning technology was employed in this process. The chemical structure, surface morphology, mechanical properties, hydrophilicity, thermal stability, and biocompatibility of PVA-ACS nano-sensing label were investigated. Moreover, the PVA-ACS nano-sensing label exhibited sensitive color responsiveness and reversible color switching, and the properties enabled the naked-eye inspection of meat freshness during production, processing and transportation. Furthermore, a strategy incorporated the nano-sensing labels with a smartphone was developed to record color information in conjunction with the color recognition software (ColorColl). This work provided a valuable perspective for real-time freshness monitoring with high satisfaction and efficiency, opening new possibilities for meat quality grading.