Abstract: Roselle anthocyanins were acylated and acylated anthocyanins with higher thermal and light stability were obtained. Then, a smart indicator film was prepared using polyvinyl alcohol and β-cyclodextrin as film-forming substrates and acylated anthocyanins as an indicator. Its mechanical properties, color response sensitivity and stability were investigated. The tensile strength of polyvinyl alcohol/β-cyclodextrin/acylated roselle anthocyanin (PCRA) film was more than three times as high as that of polyvinyl alcohol/β-cyclodextrin/roselle anthocyanin (PCR) film, and the microstructure of the PCRA film was more compact. In addition, the water vapor transmittance of the PCRA film was 2.06 × 10-6 g/(m·h·Pa) and higher than that of the PCR film. The stability of the PCRA film was higher while the color response sensitivity was lower. Then, the PRCA film was applied as an indicator for monitoring beef freshness at 4 ℃. The total volatile base nitrogen (TVB-N) content of beef increased to 16.81 mg/100 g on the sixth day of storage, indicating that the beef was spoiled. The color of the PCRA film changed from pink to yellow-green, which could effectively reflect the freshness of beef. Finally, we found a high correlation coefficient between the physicochemical information of beef and the color information of the indicator film, further confirming that the visual film can be applied to monitor beef freshness. The results of this study provide a basis for the development of intelligent food packaging in the future.

Key words: acylated roselle anthocyanins; stability; beef freshness; intelligent indicator film; sensitivity