Active and intelligent collagen films containing laccase-catalyzed mulberry extract and pickering emulsion for fish preservation and freshness indicator

Given the growing emphasis on food safety, the need for functionalized packaging is becoming more prominent. Cinnamon essential oil (CEO)-based Pickering emulsions can impart excellent anti-bacterial and anti-oxidant activities to collagen films through slow-release actives, but the resultant films exhibit reduced water resistance and mechanical properties that may limit their application. In this study, oxidized mulberry extract (OME) was prepared by laccase oxidation and used as an enhancer to improve the physicochemical properties of CEO-based Pickering emulsion collagen films. The incorporation of OME enhanced the tensile strength (79.18–106.35 MPa) and water resistance (water vapor permeability, 2.82–2.30 × 10−11 (g·m−1·s−1·Pa−1); water sorption, 524.57%–201.28%) of the films. The films also exhibited superior light-blocking, antioxidant, and antibacterial activities as well as pH sensitivity. When the COL-PE/OME 4 film was used for fish preservation, a four-day extension of shelf life was observed and the film showed a visible color change (ΔE > 5) from red (day 0) to blackish-green (day 12) reflecting the degree of freshness of the stored fish. These findings indicate the potential of the functionalized collagen films for fish preservation and indicators of freshness.