Incorporating lipid microparticles into carboxymethyl cellulose films as secondary carriers for stable loading and sustained releasing of carvacrol

Abstract

Active compounds were always incorporated into biopolymer films in order to enrich and/or enhance their functions. However, the strong volatility of the active compounds and the weak interactions between the compounds and the polymer matrix always leads to an initial burst release and later unstable load of the volatile compounds. Thus, in order to develop a composite film with the function of sustained release of active substance, stearic acid (SA) was incorporated into carboxymethyl cellulose (CMC) films as a secondary carrier for the carvacrol loading and releasing. A two-step homogenization method including high-speed shear homogenizer (HSH) and high-press homogenizer (HPH) was employed to modify the film-forming emulsions. Lipid particle size and rheology behavior of the emulsions were determined, and the microstructure of their final films was characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The release behavior of carvacrol from the films was also investigated as well. The results showed that the greatest intensity of homogenization (HSH at 22,000 rpm for 3 min plus HPH at 60 MPa for 10 cycles) resulted in the lowest lipid particle size in the film-forming emulsion and the most homogenous internal structure in final films. The release behavior of carvacrol indicated that the controllable size and distribution of lipid particles could be an effective method to ensure the sustained release of carvacrol from polysaccharide-based films, and furtherly regulate the release rate in a certain range.