Assessment of Rugulopteryx okamurae seaweed as source of sustainable alginate gels with polyphenols from orange peel

This study explores the utilization of an invasive brown seaweed from the Strait of Gibraltar, Rugulopteryx okamurae (RO), as a source for alginate. Extracted alginate was used to create a hydrogel matrix for the encapsulation of polyphenols extracted from orange peel (OP). This approach addresses two environmental challenges: the ecological threat posed by RO and the significant waste generated by orange production. Around 2.5 Mtons of orange waste are annually produced in the European Union, being OP the main fraction (40–55% w/w). The alginate was gelled using calcium salts, and the resulting gels were then fortified with OP extracts. The addition of these polyphenols significantly improved the mechanical properties of the gels, leading to higher viscoelastic moduli. Although water absorption was not affected, the gels exhibited enhanced water-holding capacity and reduced material loss when immersed in water. This is likely due to the promotion of hydrogen bonding by the polyphenolic compounds, which strengthens the gel network. Spectrophotometric analysis confirmed the successful encapsulation of the OP polyphenols within the alginate matrix. A Life Cycle Analysis (LCA) of the alginate extraction process identified electricity consumption and wastewater treatment as key environmental impact factors. This research highlights a promising, sustainable method to convert an ecological issue into a valuable resource for developing encapsulation systems with improved functional properties.