Functional and structural effects of hydrocolloids on Ca(II)-alginate beads containing bioactive compounds extracted from beetroot

Abstract

In the present research, valuable bioactives such as betacyanin and polyphenols of beetroot leaf and stem (a food waste) were extracted and encapsulated in Ca(II)-alginate beads, using sucrose, arabic and guar gums, and low and high methoxyl pectins as excipients. A complete SAXS evaluation from the molecular to the supramolecular changes (1–100 nm) produced by excipients and extracts on the microstructure of the hydrogel network was performed. Thus, combining structural-functional information allows for the design of Ca(II)-alginate systems based not only on functional aspects. Here we demonstrate that the presence of hydrocolloids affected the alginate dimers size and density, the rods size and compactness as well as their interconnectivity. Nevertheless, these modifications can be overlied by the presence of an extract, which leads to alginate coordination prior to gelation, strongly affecting the resulting microstructure. Among the used hydrocolloids, only guar gum achieves the two proposed criteria: increasing functional properties and generating stable microstructural modulations.