The pH-response color-changeable films were prepared by adding different contents (1 %, 2 % and 3 %) of hyacinth bean anthocyanins (HBA) into guar gum/polyvinyl alcohol blend matrix. The structural characterization and optical, barrier, mechanical, thermal, antioxidant and color-changeable properties of the films were determined. The films were applied to monitor the freshness of chilled shrimp and pork. Results showed that HBA were pH-dependent color-changeable pigments that endowed the films with purple color. 2 % and 3 % of HBA improved the uniformity and compactness of the films by forming hydrogen bonds with film matrix. The barrier ability of the films against UV-vis light, water vapor and oxygen was significantly elevated by 2 % and 3 % of HBA. The mechanical, thermal and antioxidant properties of the films were improved by HBA. The films containing HBA were much sensitive to pH variation and ammonia vapor, presenting obvious color changes (purple→green→yellow-green). The films containing HBA showed good color stability when stored at 4 °C for 30 days. Moreover, the film containing 2 % HBA showed color changes (purple→green) when the chilled shrimp and pork decayed. The results suggested that the film containing 2 % HBA was suitable to monitor the freshness of meat products in intelligent packaging field.
Keywords: Anthocyanins; Color-changeable films; Guar gum; Hyacinth bean; Intelligent packaging.
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