Functional design of sage seed galactomannan based-films with gelled double emulsion strategy activated by co-incorporating rosemary extract and Zataria multiflora essential oil

This study explored active film development using gelatin and sage seed gum through various gelled double emulsions strategies, including W 1g /O/W 2 , W 1 /O g /W 2 , and W 1g /O g /W 2 which were fortified with rosemary extract (RE) and Zataria multiflora essential oil (ZMEO). SEM images confirmed the successful creation of a denser and smoother film surface by incorporating RE and ZMEO . Although, roughness increased after the gelation of each inner water and oil phase, no pores and cracks were observed in these films. In contrast, microstructural attributes (i.e., smooth and homogeneous surface) were improved in W 1g /O g /W 2 , suggesting the enhancement effect of gelation of both water and oil phases. XRD spectra showed no change in film crystallinity in the presence of RE and ZMEO, however; it was increased after gelation. The incorporation of ZMEO and rosemary extract, as well as the gelation of both inner water and oil phases, modified the mechanical properties in terms of tensile strength and elongation at break. Water vapor permeability, solubility, and swelling of films decreased with the addition of ZMEO due to its hydrophobic nature. Antioxidant activity using the DPPH radical scavenging assay and antibacterial activity against Listeria monocytogenes and Pseudomonas aeruginosa using the determination of inhibition zone also confirmed the significant effect of ZMEO and RE to design active films. The gelation of the inner water and oil phases, individually or simultaneously, had no significant effect on antioxidant activity; however, it enhanced antibacterial activities due to the prolonged exposure of bacteria to the controlled release of bioactives. Therefore, the gelled double emulsion strategy by co-encapsulation of hydrophilic and hydrophobic bioactives can provide functional active films with ideal physical and mechanical properties.