Polyvinyl Alcohol/Starch-Based Film Incorporated with Grape Skin Anthocyanins and Metal-Organic Framework Crystals for Colorimetric Monitoring of Pork Freshness

• An intelligent film for the visual monitoring of pork freshness was developed. • GSAs extracted from “kyoho” grape skin were used as pH-sensitive indicators. • MIL-101 with good volatile amine enrichment capability was introduced to the film. • The sensitivity of the freshness film was improved by incorporation with MIL-101. • As-prepared film is able to real-timely monitor pork freshness in package. An intelligent film for the visual monitoring of pork freshness was developed using degradable polyvinyl alcohol (PVA)/starch (PS) to immobilize the chromogenic agent of anthocyanins and the volatile amine collector of metal–organic frameworks (MOFs). The indicative property of grape skin anthocyanins (GSAs) was verified using the UV–vis spectra, corresponding to multi-color changing in a pH range of 2–12. Interestingly, the introduction of MIL-101 crystals in the PS/GSAs film significantly increased the specific surface area (approximately 10 times) of the film, the superior volatile amine enrichment capability of MIL-101 enabling the film to detect freshness with a high degree of sensitivity. Moreover, the as-prepared film exhibited good antibacterial properties attributed to MIL-101, which help maintain the freshness of the pork. Owing to these advantages, the PS-GSAs/MIL-101 film was tested to real-timely monitor pork freshness in package, the results were further confirmed basis the total volatile basic nitrogen values.