Preparation of NH3- and H2S-sensitive intelligent pH indicator film from sodium alginate/black soybean seed coat anthocyanins and its use in monitoring meat freshness

The pH, ammonia, and H2S sensitivity of sodium alginate/black soybean seed coat anthocyanin (SA/BSSCA) films and their response mechanism were analyzed based on stability, intermolecular interactions, and microstructure. The results showed that the with the BSSCA content increased from 0.02% to 0.30%, SA/0.02–0.12BSSCA films had the highest color stability. The highest sensitivity to pH, ammonia, and H2S was observed for the SA/0.12–0.30BSSCA films, meanwhile, the SA/0.12BSSCA film had the highest sensitivity to meat unfreshness and spoilage. The incorporation of BSSCAs reduced the water solubility, water vapor absorption, and permeability of the films. With the BSSCA addition, the intermolecular interaction between BSSCAs and SA intensified, reducing the film roughness and number of aggregated particles, resulting in compact microstructures, which improved the film sensitivity. Thus, the SA/0.12BSSCA film was sensitive to pH, ammonia, and H2S and, therefore, meat spoilage, while having higher stability, moderate water barrier properties, and denser microstructure.