title: Structural, physical, and chemical modifications induced by microwave heating on native agar-like galactans.
abstract: Native agars from Gracilaria vermiculophylla produced in sustainable aquaculture systems (IMTA) were extracted under conventional (TWE) and microwave (MAE) heating. The optimal extracts from both processes were compared in terms of their properties. The agars' structure was further investigated through Fourier transform infrared and NMR spectroscopy. Both samples showed a regular structure with an identical backbone, β-d-galactose (G) and 3,6-anhydro-α-l-galactose (LA) units; a considerable degree of methylation was found at C6 of the G units and, to a lesser extent, at C2 of the LA residues. The methylation degree in the G units was lower for MAE(opt) agar; the sulfate content was also reduced. MAE led to higher agar recoveries with drastic extraction time and solvent volume reductions. Two times lower values of [η] and M(v) obtained for the MAE(opt) sample indicate substantial depolymerization of the polysaccharide backbone; this was reflected in its gelling properties; yet it was clearly appropriate for commercial application in soft-texture food products.
authors.affiliation: REQUIMTE, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal.
authors.forename: Ana M M
authors.initials: AM
authors.lastname: Sousa
authors.forename: Simone
authors.initials: S
authors.lastname: Morais
authors.forename: Maria H
authors.initials: MH
authors.lastname: Abreu
authors.forename: Rui
authors.initials: R
authors.lastname: Pereira
authors.forename: Isabel
authors.initials: I
authors.lastname: Sousa-Pinto
authors.forename: Eurico J
authors.initials: EJ
authors.lastname: Cabrita
authors.forename: Cristina
authors.initials: C
authors.lastname: Delerue-Matos
authors.forename: Maria Pilar
authors.initials: MP
authors.lastname: Gonçalves
mesh_terms: D000362:Agar / Q000737:chemistry*; D055598:Chemical Phenomena; D005685:Galactans / Q000737:chemistry*; D044724:Gracilaria / Q000737:chemistry*; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D008872:Microwaves; D055585:Physical Phenomena; D010936:Plant Extracts / Q000737:chemistry*
chemical_list: D005685:Galactans; D010936:Plant Extracts; D000362:Agar