Gelatin and high methyl pectin coacervates crosslinked with tannic acid: The characterization, rheological properties, and application for peppermint oil microencapsulation

In this study, gelatin and high methyl pectin coacervates were crosslinked with tannic acid (TA), and the protein conformation, microstructure, rheology, powder crystallinity, and thermal properties were investigated. Crosslinking of coacervates using TA altered the secondary structure of gelatin. Circular dichroism revealed significant changes in the alpha helix and random coil, while Fourier transform infrared spectra (FTIR) showed a spectra change of protein amine groups due to coacervate crosslinking. The hardening of gelatin and high methyl pectin coacervates with TA significantly increased the size from 18 mu m to 36 +/- 2.3 mu m. Crosslinked coacervates had a higher storage modulus (G'), with significantly improved melting and gelling points; an indication of enhanced intermolecular bonding after crosslinking. X-ray diffraction peaks of the powder showed a higher intensity in coacervates treated with TA, which was attributed to the increase in gelatin helix. Thermal gravimetric analysis data revealed that the crosslinking of coacervates using TA improved thermal properties. TA-crosslinked coacervates were used to produce peppermint oil multinuclear microcapsules with an average particle size of 47 mu m, encapsulation efficiency of 75.4% and improved thermal stability.