Smart carrageenan/carboxymethyl cellulose films combined with zein/gellan gum microcapsules encapsulated by composite anthocyanins for chilled beef freshness monitoring

The demand for smart packaging to monitor food spoilage is increasing. In the present study, composite anthocyanin microcapsules (CAM) were prepared by using zein and gellan gum as wall materials and protecting composite anthocyanin (CA). Carrageenan (Car)/sodium carboxymethylcellulose (CMC)-based indicator films (CC) containing CAM microcapsules were developed for monitoring the freshness of beef. The results demonstrated that the composite anthocyanins could be well dispersed in the CC matrix. CAM significantly reduced the effects of light and temperature on the stability of anthocyanins. CAM significantly improved the thermal stability, barrier properties and tensile strength of the films. The infrared spectra showed that the components of the indicator films were structurally similar and well-compatible. Among them, the indicator film CC/CAM-3 had the highest tensile strength (17.76 MPa), the lowest water vapor transmission rate (1.35 × 10−11 g/m·s·Pa) and a tight and neat cross-section. The color of the indicator film changed significantly in the ammonia environment: pink→blue-green→yellow. Applying different concentrations of indicator films to beef freshness monitoring, we found that beef reached sub-freshness and spoilage on days 4 and 7, respectively, and accordingly the indicator film CC/CAM-3 changed from pink to purple and green. To examine its capability as a colorimetric indicator film, we related the change in beef quality to the ΔE value of the indicator film, which proved to be the most sensitive when used to monitor the freshness grade of beef, as demonstrated by the indicator film CC/CAM-3.