Novel anthocyanin electrospun film by caffeic acid co-pigmentation for real-time fish freshness monitoring

Abstract Intelligent and efficient food freshness indicators（FFI）are important. In this work, the FFI for real-time fish freshness monitoring was fabricated by electrospinning with polyacrylonitrile as polymer, blueberry anthocyanins as indicator, and caffeic acid as a co-pigment. The color of nanofiber film changed in the presence of alkaline gas, and this was because the volatile ammonia combined with water to form NH3·H2O, then NH3·H2O were hydrolyzed to form OH- and NH4+. The color of polyacrylonitrile-anthocyanins nanofiber films was caused by OH-. Comparing to the polyacrylonitrile-anthocyanins film without caffeic acid, the polyacrylonitrile-anthocyanins-caffeic acid film had enhanced significantly ammonia responsiveness with total color difference values of 29.897. And it was also observed that the addition of caffeic acid obviously improved the storage stability. When using polyacrylonitrile-anthocyanin-caffeic acid film to detect fish freshness, the color change (pink, light purple, dark purple) can be clearly seen with the naked eye, which was closely related to the change of volatile base nitrogen. This study provided a reference for detecting food freshness using co-pigmentation and electrospinning encapsulation technology in combination.