title: Analysis of the Thermal Degradation of the Individual Anthocyanin Compounds of Black Carrot (Daucus carota L.): A New Approach Using High-Resolution Proton Nuclear Magnetic Resonance Spectroscopy.
abstract: The black carrot dye is a mixture of cyanidin molecules, the nuclear magnetic resonance (NMR) spectrum of which shows a highly overlapped aromatic region. In this study, the (1)H NMR (800 MHz) aromatic chemical shifts of the mixture were fully assigned by overlaying them with the characterized (1)H NMR chemical shifts of the separated compounds. The latter were isolated using reverse-phase high-performance liquid chromatography (RP-HPLC), and their chemical shifts were identified using (1)H and two-dimensional (2D) correlation spectroscopy (COSY) NMR spectroscopy. The stability of the black carrot mixture to heat exposure was investigated at pH 3.6, 6.8, and 8.0 by heat-treating aqueous solutions at 100 °C and the powdered material at 180 °C. From integration of high-resolution (1)H NMR spectra, it was possible to follow the relative degradation of each compound, offering advantages over the commonly used ultraviolet/visible (UV/vis) and HPLC approaches. UV/vis spectroscopy and CIE color measurements were used to determine thermally induced color changes, under normal cooking conditions.
authors.affiliation: †EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, United Kingdom.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Iliopoulou
authors.affiliation: ‡Macphie of Glenbervie, Stonehaven AB39 3YG, United Kingdom.
authors.forename: Delphine
authors.initials: D
authors.lastname: Thaeron
authors.affiliation: ‡Macphie of Glenbervie, Stonehaven AB39 3YG, United Kingdom.
authors.forename: Ashley
authors.initials: A
authors.lastname: Baker
authors.affiliation: †EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, United Kingdom.
authors.forename: Anita
authors.initials: A
authors.lastname: Jones
authors.affiliation: †EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, United Kingdom.
authors.forename: Neil
authors.initials: N
authors.lastname: Robertson
mesh_terms: D000872:Anthocyanins / Q000737:chemistry*; D018552:Daucus carota / Q000737:chemistry*; D006358:Hot Temperature; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010936:Plant Extracts / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D010936:Plant Extracts; C017154:cyanidin
keywords: CIE color measurements; NMR integration; UV/vis spectroscopy; acylation; anthocyanins; cyanidin; thermal degradation