Fucoidan-based cinnamaldehyde nano-emulsion: Fabrication by complex coacervation and application in apple juice

Cinnamaldehyde (CIN) is widely used in food industry due to multiple biological functions. However, CIN suffers from bad odor, high volatility, low solubility in water and sensitivity to oxygen, which limits its application. In this study, fucoidan/chitosan (FUC/CS) nanocarrier was prepared by complex coacervation method to encapsulate CIN. The nano-complexes prepared at pH 5 and in a ratio (FUC/CS) of 10:1 exhibited particle size of 330-360 nm, a zeta potential closed to -30 mV and a PDI of 0.16 with an EE and LC of 70.03 % and 54.9 %, respectively. Confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM) showed that the prepared FUC/CS/CIN was more uniform. Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy observed a strong electrostatic interaction between FUC and CS and covalent interaction between CIN and CS. Higher antioxidant properties were found in encapsulated CIN. Fucoidan/Chitosan/Cinnamaldehyde has a synergistic effect with ascorbic acid (AA) in slowing down the browning of apple juice. The inhibitory efficiency of encapsulation CIN against Escherichia coli (E. coli) and Listeria monocytogenes (LM) was significantly increased compared to free CIN. In summary, the encapsulation of CIN in FUC/CS by the complex coacervation method can effectively improve its stability.