Properties and applications of curcumin and perilla essential oil emulsion-based freshness-indicating films in golden pomfret (Trachinotus ovatus) freshness extension

To develop intelligent, green fish freshness-indicating films, we evaluated the physicochemical properties (Mechanical strength, moisture barrier capability, thermal stability, and antioxidant activity) of chitosan titanium dioxide (CS-TiO₂) composite particle perilla essential oil lotion with different addition levels (1%, 3%, 5%, and 7%, w) and the freshness-indicating films (EP1, EP3, EP5, and EP7) prepared from curcumin and gelatin. Additionally, we assessed the preservation efficacy of the films on golden pomfret (Trachinotus ovatus) by monitoring total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), carbonyl content, total sulfhydryl content, antibacterial activity, and freshness-indicating performance. Pure gelatin film (EP0) served as the control. Results demonstrate that all CS-TiO₂-incorporated films exhibited significantly enhanced properties compared with EP0. EP7 films exhibited excellent mechanical properties (Tensile strength 38.34 MPa, elongation at break 25.80%) and moisture resistance (Dissolution rate 32.16%, swelling rate 152.18%). They also demonstrated outstanding barrier properties (Water vapor transmission rate 3.04×10⁻¹³ g·m⁻¹·s⁻¹·Pa⁻¹) and antioxidant activity (DPPH scavenging rate 45.97%, ABTS scavenging rate 87.36%). When applied to the refrigerated preservation of golden pomfret, the films effectively inhibited fish spoilage. After 7 d, TVB-N and TBARS values were controlled at 22.36 mg·100 g ⁻¹ and 0.53 mg·kg⁻¹, respectively, while significantly maintaining protein oxidation stability (Carbonyl content 55.89 μmol·mg⁻¹, total sulfhydryl content 48.86 μmol·mg⁻¹). For freshness indication, the EP7 group exhibited significant color changes from pale yellow to russet with prolonged storage, correlating with freshness deterioration. Therefore, curcumin and perilla essential oil emulsion-based freshness-indicating films in this research can not only extend the shelf life, but also intelligently indicate the freshness of fish.