Droplet-based millifluidic technique for encapsulation of cinnamon essential oil: Optimization of the process and physicochemical characterization

The millifluidic technique could be considered as a novel approach for encapsulation of bioactive compounds and has a promising perspective in the field of food engineering or pharmaceutical science. In this study, we aim to optimize the encapsulation of cinnamon essential oil (CEO) by droplet-based millifluidic technique with four responses: encapsulation efficiency (EE), loading capacity (LC), sphericity factor (SF) and size of calcium-alginate millicapsules. The effects of alginate concentration (20-30 g/L), flow rate of alginate (1-1.6 mL/min), and flow rate of CEO (0.6-0.8 mL/min) were considered by a Box-Behnken design. The best concentration of chitosan as a coating layer on the optimized samples was selected based on the Young modulus of millicapsules. The regression models showed the significant effect (p < 0.05) of the three variables on the characteristics of millicapsules. The optimal millicapsules with 3.58 +/- 0.23 mm diameter and 0.96 +/- 0.01 S F showed 98.96 +/- 1.2% and 70.14 +/- 1.8% EE and LC, respectively. SEM images exhibited a rough external surface which changed to a rigid and smooth surface through the chitosan coating. The results of DSC and FTIR tests demonstrated the CEO entrapment in the millicapsules without any chemical interaction with the encapsulant materials. The disarray of crystallinity structure in XRD patterns revealed the successful encapsulation of CEO in the millicapsules. The non-Fickian case II in the mouth and small intestine and anomalous transport in the stomach were the main release mechanisms in the coated millicapsules. The release profile of CEO also fitted well with Ritger-Peppas model.

Automated summary

The millifluidic technique was used to optimize the encapsulation of cinnamon essential oil (CEO). Alginate concentration, flow rate of alginate, and flow rate of CEO were found to significantly affect the characteristics of the millicapsules. The optimal millicapsules had high encapsulation efficiency and loading capacity, and the chitosan coating resulted in a rigid and smooth surface. The results showed successful encapsulation of CEO in the millicapsules, and the release mechanism was mainly non-Fickian case II. This research provides valuable insights for the fields of food engineering and pharmaceutical science.