Anthocyanins From Rosella (Hibiscus Sabdariffa) And Mulberry (Morus Alba L.): Characterization And Potential Application As Ph Indicator In Chitosan Films

Abstract

Anthocyanin-rich roselle extract (RARE) or mulberry extract (MARE) was incorporated into chitosan (CS) following the concentration of 0.30; 0.60 and 0.90 mg anthocyanins/g CS to develop pH-sensitive, ammonia-sensitive and antioxidant food packaging films. The structural, physical, and functional properties of CS-RARE and CS-MARE films were evaluated. Microstructure observation showed that at levels of 0.6 and 0.9 mg anthocyanins/g CS, the extract content significantly decreased the homogeneity of CS film matrix. Fourier transform infrared spectroscopy indicated the intermolecular interaction between CS and RARE/MARE through hydrogen bonds. The addition of RARE/MARE considerably increased the ultraviolet-visible light barrier, water vapor barrier, pH sensitivity and antioxidant activity of CS film. At 0.9 mg anthocyanins/g CS concentration, both CS-RARE and CS-MARE film showed significant color change when being exposed to pH from 5 to 7.0-7.5; however, the color change of CS RARE films was more clearly visible by naked eyes. The antioxidant capacity of CS film was increased from 126.40 to 1044.54 µg Trolox equivalents/g film when incorporated with RARE and 802.71 µg Trolox equivalents/g film when incorporated with MARE. Among developed films, there were only CS-RARE films at 0.6 and 0.9 mg/g CS anthocyanins concentration presented obvious color change responding to ammonia. This study suggested CS films containing RARE were more suitable to be used as a pH and meat spoilage indicator.