Comparative evaluation on fatty acid and Matricaria recutita essential oil incorporated into casein-based film

Sodium caseinate composite films containing lipids-oleic acid (OA), stearic acid (SA), or Matricaria recutita essential oil (MEO) - were prepared through emulsification and their physical, thermal, mechanical, and barrier properties were evaluated and compared. Furthermore, their antimicrobial effectiveness against Listeria monocytogenes, Staphylococcus aureus, and Escherichia coli was studied. Emulsified films were softer, less rigid, and more stretchable than pure films. The films' water vapor barrier properties were found to decrease upon the addition of lipid content; this effect was greatly reduced when MEO was added. The presence of OA/SA and MEO decreased tensile strength and elastic modulus but increased the elongation at break. Thermal analysis of all emulsified films showed two endothermic peaks; these results confirmed those obtained by SEM studies, where a partial separation of the two phases occurred. The films' antimicrobial activities were increased by incorporating lipids, particularly those containing MEO, which were more effective against the studied bacteria. This work showed that when taking all the studied variables into account, films formulated with MEO were found most suitable for various food applications.