Characterization of anthocyanin-loaded microparticles produced with PEG and guar gum

The complexation of natural pigments with biopolymers can be an interesting approach to improve their stability under different conditions, making these compounds less susceptible to oxidizing and degrading agents. In this context, the aim was to develop dispersions produced containing hibiscus extract (Hibiscus sabdariffa L - EH) with polyethylene glycol (PEG-4000 g.mol-1) and guar gum (GG), and to evaluate their interactions in terms of zeta potential (ζ) and Fourier transform infrared spectroscopy (FTIR). PEG:EH and GG:EH dispersions were produced with a mass ratio of 10:3 (m/m), and PEG:GG:EH with a mass ratio of 5:5:3 (m/m), respectively. PEG:EH, GG:EH and PEG:GG:EH presented a ζ-potential of -3.37mV ±0.42, -4.2mV ±0.50 and 2.1mV ±0.69 at pH 3.0, and -6.53mV ±0.66, -1.58mV ±0.78 and -7.04mV ±0.70 at pH 5.0, respectively. In general, it is possible to observe that GG had little influence in this parameter, as expected, since GG possesses non-ionized groups in its moleculares structure, which means that the ζ-potential was mainly affected by the pH. FTIR spectra show some bands at 3400-3200 cm-1 range for all the treatments, which can be attributed to the presence of hydroxyl groups, possibly due to the hygroscopic nature of the constituents of the dispersions. In addition, the band at 1600 cm-1 indicates the presence of groups C=C, present in aromatic compounds, meaning that the anthocyanin-loaded complexes were successfully produced. Complexation between natural pigments and biopolymers can be interesting to pursue for application to food matrices.