Preparation and Characterization of Indicator Films Based on Carrageenan-Based Microcapsules Containing Anthocyanins for Monitoring the Quality of Beef during Storage

The aim of this study to develop a stable anthocyanin indicator film to monitor the freshness of chilled beef. Composite anthocyanin microcapsules (CAM) were prepared and used to prepare indicator films using carrageenan (Car) and sodium carboxymethyl cellulose (CMC) as film-forming matrix with different amounts (5%, 10%, 15% and 20%, V/V) of added CAM, and the structural and physical properties of the resulting films were characterized, and their application to monitor beef freshness was investigated. The results showed that the addition of CMC significantly improved the mechanical properties, barrier properties and thermal stability of Car films. The film with 15% CAM had the highest tensile strength (17.76 MPa) and lowest water vapor transmission rate (1.35 × 10^-11 g/(m·s·Pa)), and showed a tightly and orderly arranged cross-section. The Fourier transform infrared spectra showed that the components of the indicator film were structurally similar and compatible. When the indicator film was exposed to ammonia, its color changed from pink to blue-green and eventually to yellow. The indicator film was applied to monitor the freshness of beef during storage at 4 ℃. The results showed that beef reached secondary freshness and spoilage on day 4 and 7, respectively, and that the color of the indicator film changed from pink to purple and green correspondingly. In conclusion, the film with 15% CAM is the most sensitive to changes in the freshness of beef and thus can be used to detect it.