title: Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: Inhibition by Maillard reaction.
abstract: Under roasting conditions, polysaccharides depolymerize and also are able to polymerize, forming new polymers through non-enzymatic transglycosylation reactions (TGRs). TGRs can also occur between carbohydrates and aglycones, such as the phenolic compounds present in daily consumed foods like coffee. In this study, glycosidically-linked phenolic compounds were quantified in coffee melanoidins, the polymeric nitrogenous brown-colored compounds formed during roasting, defined as end-products of Maillard reaction. One third of the phenolics present were in glycosidically-linked form. In addition, the roasting of solid-state mixtures mimicking coffee beans composition allowed the conclusion that proteins play a regulatory role in TGRs extension and, consequently, modulate melanoidins composition. Overall, the results obtained showed that TGRs are a main mechanism of phenolics incorporation in melanoidins and are inhibited by amino groups through Maillard reaction.
authors.affiliation: QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: ana.moreira@ua.pt.
authors.forename: Ana S P
authors.initials: AS
authors.lastname: Moreira
authors.affiliation: CQ-VR, Chemistry Research Centre, Department of Chemistry, University of Trás-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal. Electronic address: fnunes@utad.pt.
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Nunes
authors.affiliation: CQ-VR, Chemistry Research Centre, Department of Chemistry, University of Trás-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal. Electronic address: cristianapsimoes@live.com.pt.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Simões
authors.affiliation: QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal; CESAM, Department of Biology, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: elisabete.maciel@ua.pt.
authors.forename: Elisabete
authors.initials: E
authors.lastname: Maciel
authors.affiliation: QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: p.domingues@ua.pt.
authors.forename: Pedro
authors.initials: P
authors.lastname: Domingues
authors.affiliation: QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: mrd@ua.pt.
authors.forename: M Rosário M
authors.initials: MR
authors.lastname: Domingues
authors.affiliation: QOPNA, Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: mac@ua.pt.
authors.forename: Manuel A
authors.initials: MA
authors.lastname: Coimbra
mesh_terms: D002241:Carbohydrates / Q000737:chemistry; D040503:Coffea / Q000737:chemistry*; D003069:Coffee / Q000737:chemistry; D006031:Glycosylation; D006358:Hot Temperature; D015416:Maillard Reaction; D010636:Phenols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*
chemical_list: D002241:Carbohydrates; D003069:Coffee; D010636:Phenols; D011108:Polymers; C011908:melanoidin polymers
keywords: Maillard reaction; Melanoidins; Phenols; Roasting; Transglycosylation