Controlled release mechanism of complex bio-polymeric emulsifiers made microspheres embedded in sodium alginate based films

Abstract

Sodium alginate (SA) bio-based films embedded with cinnamon essential oil (CEO) microspheres encapsulated in complex bio-polymeric emulsifiers (CBE) were fabricated and characterized. CBE were composed of gelatin (G0)/gum acacia (A0), G0/carboxymethylcellulose sodium (C0) and G0/A0/C0, respectively, compared with single bio-polymeric emulsifier G0 as control. Emulsion morphology results suggested substantial microspheres were formed in all emulsions, and particle distribution results showed that CBE had significant influence on D [3, 2] (P < 0.05) of emulsions compared with control. FTIR spectra indicated different electrostatic interactions formed among CBE compositions, and CEO retained unchanged. SEM photographs depicted that each resulting film had an asymmetric cross-section microstructure with compact polymer-rich phase on top side (T) and porous microsphere-rich phase on bottom side (B). The diffusion coefficient (D) representing release rate of CEO increased significantly with the decrease of electrostatic interaction force among CBE. Besides, Ds of CEO releasing through T were approximately one-fourth of that though B of all films, implying length of CEO release route was also a key factor in release control. With moderate mechanical properties having been tested, the obtained bio-based SA films embedded with CBE made microspheres could be potentially applied as active packaging controlling the release rates of the encapsulated CEO for the protection of food inside.