Improvement of properties of smart ink via chitin nanofiber and application as freshness indicator

Chitin nanofiber decorated with both cationic (NH 3 + ) and anionic (COO − ) is fabricated by partial deacetylation and TEMPO-oxidation (TEMPO/NaClO 2 /NaClO) system. As-prepared zwitterionic chitin nanofiber has particle size around 395 nm and excellent dispersibility. It could synergize with chitosan to immobilize anthocyanin for manufacturing smart ink, which is proved to be mainly stabilized by hydrogen bond. Chitin nanofiber could improve the rheology properties including yield stress and shearing viscosity of the ink, and result in excellent printability with rub resistance and tape fastness being up to 97.8 % and 98.9 % respectively. The screen-printed label (based on smart ink) displays different colors and shows certain color change trend under different pH conditions. Analysis of the volatile basic nitrogen, CIE Lab (Commission International Eclairage color model) and pH demonstrates the effective indicating properties of the label for fish freshness level. The application on fish proves that this screen-printed label could be an easy, green way to determine the meat freshness.