Hazelnut Protein and Sodium Alginate Complex Coacervates:\nAn Effective Tool for the Encapsulation of the Hydrophobic Polyphenol\nQuercetin

For valorization\npurposes of hazelnut byproducts, complex coacervation\nof hazelnut protein isolate (HPI) with sodium alginate (NaAlg) was\ninvestigated by turbidimetric analysis and zeta potential determination\nas a function of pH and protein/alginate mixing ratio. HPI-NaAlg complex\ncoacervates were used as an encapsulating material of quercetin (QE)\nat different concentrations. The optimal pH and mixing ratio resulting\nin the highest turbidity and neutral charge were 3.5 and 6:1, respectively.\nThe coacervation yield was 74.9% in empty capsules and up to 90.0%\nin the presence of QE. Under optimal conditions, HPI-NaAlg complex\ncoacervates achieved an encapsulation efficiency higher than 99% in\nall coacervate/QE formulations. Fourier transform infrared spectroscopy\n(FTIR) results revealed the occurrence of electrostatic interactions\nbetween different functional groups within the ternary complex in\naddition to hydrogen and hydrophobic interactions between QE and HPI.\nHPI-NaAlg complex coacervates can serve as an alternative matrix for\nthe microencapsulation of bioactive ingredients with low water solubility\nin food formulations, which adds an additional valorization of hazelnut\nbyproducts.