Natural silk improves the physico-mechanical properties of the colorimetric aerogel composed of anthocyanin, carboxymethyl cellulose and sodium alginate for fish freshness indication

This study aimed to develop a natural colorimetric aerogel based on carboxymethyl cellulose (CMC), sodium alginate (SA), black goji anthocyanin (BGA), and various natural fibers such as cotton fiber (CF), silk fiber (SF), and down fiber (DF) via a freeze-drying approach for monitoring fish freshness. Various colorimetric aerogels, including CMC/SA, CMC/SA/CF, CMC/SA/SF, and CMC/SA/DF were developed and structurally characterized using SEM, FTIR, XRD, TGA, TPA, and BET. CMC/SA aerogel showed higher density (0.054 g/cm 3 ) with no surface pores, while CMC/SA/SF had a large surface area (18.6214 m 2 /g) with uniformly higher porosity (97.113 %) and a lower density (0.024 g/cm 3 ). Moreover, the CMC/SA/SF aerogel exhibited higher mechanical properties and color sensitivity at various pH compared to other aerogels, which was then used as an indicator label for monitoring fish freshness during storage at 4 °C and 25 °C. The label aerogel became blue from purple, when TVB-N and pH values reached 20.03 mg/100 g and 19.50 mg/100 g and pH 6.67 and 6.67 at 4 and 25 °C, respectively, exhibiting fish deterioration. Taken together, the colorimetric aerogel composite CMC/SA/SF shows great potential for application as an intelligent package in monitoring the freshness of fish.