Influence of egg albumin and whey protein in the co-encapsulation of betalains and phenolic compounds from Bougainvillea glabra bracts in Ca(II)-alginate beads

Abstract

Bougainvillea glabra bracts aqueous extract was co-encapsulated in Ca(II)-alginate beads, with the inclusion of egg albumin and whey protein isolate. Rheological measurements of the dispersions prepared in advance to beads formation showed a viscosity reduction by WPI, however, albumin increased the viscosity due to higher intermolecular association with alginate, as confirmed by FT-IR. The beads supplemented with proteins showed higher encapsulation efficiencies, with values higher than 70% for phenolic compounds and 50% for betalains. Rupture strength varied from 31.1 to 38.9 N for beads containing whey protein and albumin, respectively, indicating that the inclusion of these proteins resulted in beads with different mechanical properties and applications. Thermogravimetric analysis and FT-IR indicated molecular interactions between B. glabra compounds, sodium alginate, and proteins. The beads structural characterization determined by Small Angle X-ray Scattering demonstrated that Ca(II)-alginate microstructure was highly affected by proteins, especially albumin, revealing strong interactions between these biopolymers. Novelty impact statement: This study employs a novel matrix to encapsulate phenolic compounds and betalains from B. glabra bracts in Ca(II)-alginate beads using egg albumin and whey protein isolate to reinforce the structure of the beads and improve their chemical stability. Small Angle X-ray Scattering (SAXS) technique showed that proteins affected the beads microstructure, revealing strong interaction with Ca(II)-alginate. The inclusion of egg albumin and whey protein resulted in beads with different mechanical properties allowing their application in several food products.