Shrimp (Litopenaeus vannamei) muscle proteins as source to develop edible films

Edible films were successfully obtained from shrimp (Litopenaeus vannamei) muscle protein plasticized with glycerol. The effects of pH, thermal treatment, and the addition of a natural cross-linker (cinnamaldehyde) to the film-forming solution on the properties of the resulting films were evaluated. The pH was found to be a key parameter that greatly influenced the properties of the films, those produced at pH 2 showing higher mechanical properties, water resistance, transparency, and UV barrier properties than those produced at pH 11. Extensive proteolysis and lower protein cross-linking were evidenced in pH 11 films, as determined by SDS-PAGE and infrared spectroscopy (ATR-FTIR). The application of thermal treatment (80 °C/15 min) gave rise to considerable protein cross-linking, resulting in an improvement in mechanical properties, water resistance, and transparency of films produced at pH 11. The treatment with 5 g of cinnamaldehyde/100 g protein at pH 2 produced the film with the best physicochemical properties. Films produced at pH 2 with or without cinnamaldehyde had antimicrobial effects on fish spoilage bacteria, and the one containing cinnamaldehyde was stable after 30 days of storage at 17 °C and 58% relative humidity.