Amine-Responsive Bilayer Indicator Films Based on Black Wolfberry Anthocyanin and Hydrophobically Modified TiO2 for Real-Time Meat Freshness Monitoring
In this study, amine-responsive bilayer films (agar/black wolfberry anthocyanin (AG/BWA) and agar/black wolfberry anthocyanin/sodium alginate/hydrophobically modified TiO 2 nanoparticles (AG/BWA/HM)) were fabricated. These films consist of a sensing layer made of agar/anthocyanin and a protective layer composed of sodium alginate and hydrophobically modified TiO 2 nanoparticles (HMTI). The fabrication process involved the solvent evaporation method and screen-printing technique, with anthocyanins extracted from black wolfberry serving as the key component in the sensing layer. The prepared films were characterized by FTIR, SEM, XRD, and UV spectroscopic techniques. Water contact angle measurements showed that the AG/BWA/HM film was hydrophobic (> 90°). The incorporation of anthocyanins increased the tensile strength of the films by 6–10 MPa, the elongation at break by 3–6%, and the water solubility by 4–15% compared to control films (agar film). Light stability and storage stability tests revealed that the incorporation of hydrophobically modified TiO 2 effectively enhanced the stability of the films. When exposed to different pH values, the bilayer films showed different color changes, with a significant change from acidic to basic. The ammonia vapor test showed that the sensitivity of the AG/BWA/HM film was improved by 20.1% compared to the AG/BWA film. The indicator film was used to monitor the deterioration of pork at room temperature (25 ℃), and the color of the AG/BWA/HM film changed significantly with the increase of total volatile basic nitrogen (TVBN) of pork stored at room temperature (25 ℃) for 24 h as the freshness of pork changed gradually, indicating the promising application of this double-layer indicator film in the monitoring of meat freshness. Graphical
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