Development of pH response film based on potato starch/polyvinyl alcohol using Kyoho grape skin extract to monitor pork freshness

In this study, the optimal ratio of starch and polyvinyl alcohol (PVA) was successfully selected by response surface method. The novel packaging films were fabricated by immobilizing Kyoho skin extract (KSE) within starch/PVA composite film by the casting method. The mechanical property, PH sensitivity, and other properties of films with different KSE content (1–5 mL) were studied. The starch/PVA film with 3 mL KSE (SPK3.0 film) showed more uniform structure than the starch/PVA film in microscope. At the same time, the film has strong mechanical properties and low water barrier capacity. Infrared analysis of the film further revealed hydrogen bond interaction between film matrix and KSE. The smart packaging film displayed distinguishable changes of color from purple to green in pH (1–13). Furthermore, the smart films possessed excellent antioxidant. Therefore, the SPK films had the potential application potential in the field of packaging. Highlights Barrier properties and antioxidant activity were enhanced significantly by the addition of KSE. The film components are connected by hydrogen bonds so that they have good compatibility. The functional film shows different colors in the range of pH 1–13.