Preparation and Characterization of Emulsion-Based Fucoidan-Whey Protein Film Activated With Geranium Essential Oil...

Emulsion-based edible films are novel active films that can improve food quality and their shelf life due to slow release of their active ingredient. In this study, fucoidan- whey protein (FW) composite film with different concentration of geranium essential oil (EO) nanoemulsions [0.5% (w/w) and 1% (w/w)] were prepared (FW-0.5 and FW-1). The physicochemical, thermal, morphological, and mechanical properties [tensile strength (TS), elongation at break (EB)], as well as the antioxidant and antimicrobial properties, were investigated. Gas chromatography analysis detected citronellol (30.26%), geraniol (16.41%), and linalool (12.43%) as the main compounds of geranium EO and smaller amount of monoterpene hydrocarbons (such as α-pinen, p-cymene, and limonene) and sesquiterpene alcohols (such as globulol and pogostol). Also, the addition of a higher concentration of geranium EO nanoemulsion (1%) made the film thicker (0.13 ± 0.01 mm) than the neat FW film (0.12 ± 0.01 mm) (p < 0.05). The incorporation of EO nanoemulsion reduced water vapor permeability, and FW-1 had an excellent barrier against water vapor (1.05 ± 0.28 g/m.s.Pa) when compared to the control film (1.33 ± 0.34 g/m.s.Pa) (p > 0.05). Moreover, active FW films loaded with EO nanoemulsion had lower TS and EB values (p < 0.05). TS and EB of neat FW film were 5.30 ± 0.46 MPa and 3.11% ± 0.83%, respectively, while these parameters lowered to 1.52 ± 0.65 MPa and 67.96% ± 4.70%, respectively in FW-1 (p < 0.05). Active FW films had higher L* values, lower a*, b* values, and opacity in comparison with neat FW films (p < 0.05). Moreover, the addition of EO nanoemulsions improved thermal stability, and the active FW film (FW-1) had higher thermal stability. SEM images exhibited a smooth surface in all FW films and a compact, dense structure in the cross-section of FW films loaded with EO nanoemulsion. FTIR also confirmed the encapsulation of geranium EO and its compatibility with FW films. Moreover, active FW films, especially FW-1 exhibited higher antioxidant (72.91% ± 2.53%) than FW film (35.39% ± 3.19%) and possessed stronger antimicrobial activity against Gram-negative (E. coli), Gram-positive (S. aureus) and fungi (C. albicans). This study suggested the potential applications of active FW film for food packaging.