Influence of moderate electric fields on the performance of agars extraction from Gracilaria sp.

Abstract

Seaweeds are important marine resources in Portugal, being mostly applied in the hydrocolloids industry or as food. Emerging applications include the production of high added-value bioactive compounds. Seaweed polysaccharides are water-soluble biopolymers and have a linear backbone composed of sugar units conjugated to form complex structures. The –OH groups, predominant in the polymeric chains can establish intra- and intermolecular hydrogen bonds which are excellent functional tools for gel and/or film-formation. Agar is extracted mainly from red seaweeds from Gelidiales and Gracilariales (in which group Gracilaria sp. are included). In the case of agar from Gracilaria sp., normally with inferior commercial characteristics, the functional properties are usually enhanced by an alkali pre-treatment that modifies the L-galactose-6-sulphate units into 3,6-anhydro-α-Lgalactose residues. Traditional hot water extraction is a tedious process, requires high solvent and energy consumptions and generates large amounts of waste creating the need for greener and more efficient technologies. The main objective of this work is to evaluate the influence of different electric fields intensity in the performance of the agar’s extraction from Gracilaria sp. in terms of yield, extraction time and extract’s quality.