PHYSICAL CHARACTERIZATION OF ALGINATE-BASED EDIBLE FILMS CONTAINING NANOPARTICLES OF ESSENTIAL OILS

Essential oils (EO) may be considered as food additives since they exhibit relevant antimicrobial and antioxidant properties. Nevertheless, EO incorporation in foods encounters limitations related to solubility, volatility, and changes in sensorial properties¹. Nanoemulsions provide a strategy to improve the solubility of EO. Emulsions with reduced particle size in oily-phase up to nanoscale, show enhanced stability and physical properties, compared with conventional emulsions.² Edible films could act as carriers of nanoparticles entrapped in film-forming polysaccharides matrices. Hence, films obtained from polysaccharide-based nanoemulsions containing EO, may exhibit novel and enhanced characteristics. The aim of this work was to characterize physical properties of alginate film-forming nanoemulsions containing thyme (Th), lemongrass (Lg) and sage (Sg) EO, and their corresponding films, compared with an oil-free film as control. Average droplet sizes of nanoemulsions containing Th, Lg and Sg were 82.12±3.13, 40.65±9.22 and 35.29±6.60 nm, and polydispersity indices (PDI) were 0.56±0.02, 0.49±0.08 and 0.64±0.04, respectively. Microfluidization treatment was effective to obtain reduced droplet sizes nanoemulsions, but with wide PDI indicating the presence of multiple size droplets. Films microstructure with EO were rougher than control film, following this order Lg>Th>Sg>Ct. Lg films exhibited oil body aggregates. Th and Sg film surfaces were less irregular. Opacity of control, Lg, Th and Sg films were 6.69±0.56, 9.36±2.14, 7.56±0.53 and 5.69±0.25%, respectively. The significant increase in Lg films opacity may be related with an increase of light scattering on film surface, since they exhibited the most irregular microstructure. Film thickness containing Lg and Sg EO significantly decreased (42.33±4.97 and 38.00±2.83 µm) compared with control (50.00±3.35 µm), probably due to average droplet sizes obtained in film-forming nanoemulsions. Tensile tests revealed that Elongation of Sg films (78.10±4.81%) increased compared with control (38.17±6.90%), while the others behaved similar. This study brings new information about the influence of adding EO as nanoparticles entrapped within films, over their physical properties.