Colorimetric indicator films developed by incorporating anthocyanins into chitosan‐based matrices

A novel pH‐sensitivity and antimicrobial films based on chitosan (CS), hydroxypropyl methylcellulose (HPMC), ε‐polylysine (ε‐PL) matrix by incorporating purple sweet potato anthocyanins (PSPA) through solvent casting method, has been developed. The Fourier transform infrared spectroscopic (FT‐IR) of the films showed that PSPA was added to CS/HPMC/ε‐PL matrix. The scanning electron microscopic (SEM) and X‐ray diffraction (XRD) spectra indicated that PSPA was well blend in CS/HPMC/ε‐PL‐matrix. The light transmittance rate and moisture contents (MC) of the films decreased by adding PSPA and ε‐PL. Adding an appropriate ε‐PL, the antimicrobial properties films can be improved. When the fish became spoiled, the color of the film was changed from red to green, and the total volatile basic nitrogen (TVB‐N) content was higher than that of Chinese Standard GB 2733–2015 at 36 hr. Therefore, the novel films could be applied in monitoring and packaging the freshness of fish. A novel pH‐sensitivity and antimicrobial films based on chitosan (CS), hydroxypropyl methylcellulose (HPMC), ε‐polylysine (ε‐PL) matrix incorporating purple sweet potato anthocyanins (PSPA) through solvent casting method has been developed. The scanning electron microscopic (SEM) indicated that PSPA was well blend in CS/HPMC/ε‐PL‐matrix. The films showed significant difference in color under different pH condition and good antimicrobial properties which could be applied in monitoring and packaging the freshness of fish.