title: Evaluating the role of metal ions in the bathochromic and hyperchromic responses of cyanidin derivatives in acidic and alkaline pH.
abstract: In many food products, colorants derived from natural sources are increasingly popular due to consumer demand. Anthocyanins are one class of versatile and abundant naturally occurring chromophores that produce different hues in nature, especially with metal ions and other copigments assisting. The effects of chelation of metal ions (Mg(2+), Al(3+), Cr(3+), Fe(3+), and Ga(3+)) in factorial excesses to anthocyanin concentration (0-500×) on the spectral characteristics (380-700nm) of cyanidin and acylated cyanidin derivatives were evaluated to better understand the color evolution of anthocyanin-metal chelates in pH 3-8. In all pH, anthocyanins exhibited bathochromic and hyperchromic shifts. Largest bathochromic shifts most often occurred in pH 6; while largest hyperchromic shifts occurred in pH 5. Divalent Mg(2+) showed no observable effect on anthocyanin color while trivalent metal ions caused bathochromic shifts and hue changes. Generally, bathochromic shifts on anthocyanins were greatest with more electron rich metal ions (Fe(3+)≈Ga(3+)>Al(3+)>Cr(3+)).
authors.affiliation: The Ohio State University, Dept. of Food Science and Technology, 2015 Fyffe Ct., Columbus, OH 43210-1007, United States.
authors.forename: G T
authors.initials: GT
authors.lastname: Sigurdson
authors.affiliation: Science and Discovery Group, Mars Inc., 800 High St., Hackettstown, NJ 07840, United States.
authors.forename: R J
authors.initials: RJ
authors.lastname: Robbins
authors.affiliation: Science and Discovery Group, Mars Inc., 800 High St., Hackettstown, NJ 07840, United States.
authors.forename: T M
authors.initials: TM
authors.lastname: Collins
authors.affiliation: The Ohio State University, Dept. of Food Science and Technology, 2015 Fyffe Ct., Columbus, OH 43210-1007, United States. Electronic address: Giusti.6@osu.edu.
authors.forename: M M
authors.initials: MM
authors.lastname: Giusti
mesh_terms: D000215:Acylation; D000872:Anthocyanins / Q000737:chemistry*; D003116:Color; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry
chemical_list: D000872:Anthocyanins; D007477:Ions; C017154:cyanidin
keywords: Anthocyanin; Anthocyanin-metal chelate; Aronia melanocarpa; Brassica oleracea var. capitata f. rubra; Metalloanthocyanin