Could corona-plasma treatment impact the antioxidant activity of phenolic compounds incorporated into gelatin coating applied onto PLA commercial films?

This study explores the possible impacts of the corona treatment (cold plasma) on bioactivity of natural antioxidants incorporated into fish gelatin-based composite films applied to biodegradable PLA. Indeed, physical-chemical characterisations were also investigated to better understand the potential modifications induced by the corona. The main objective was to evaluate the compatibility of corona treatment with bioactive packaging, to confirm its possible use in production and applications of active materials. Five phenolic acids (gallic, caffeic, ferulic, cinnamic, and p-coumaric) were added to the gelatin and then applied to PLA films, some of which were subsequently treated with plasma. The samples were characterized at different scales to analyze their wettability, solubility, water absorption capacity, molecular interactions (FTIR), antioxidant activity (DPPH), and UV opacity. The main results show that corona treatment slightly modifies contact angles, reflecting surface changes, without major chemical alterations of the polymer network. Neither solubility nor water absorption capacity are significantly affected by plasma, indicating weak interactions between gelatin and antioxidants. FTIR analysis confirms the absence of new covalent bonds or structural degradation of the gelatin matrix. The antioxidant activity, measured by DPPH, remains stable after treatment, proving the resistance of phenolic compounds to reactive plasma species in wet conditions. Finally, the UV opacity of the films increases significantly thanks to the antioxidants coupled with the corona process, thus improving their potential for protecting food against oxidation without being affected by corona. These results demonstrate the feasibility of corona treatment for bioactive films without compromising their functional properties and bioactivity.