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The influence of certain metal ions on the visible spectra of food dyes
Author(s) -
JONES A. V.,
THOMAS J. D. R.
Publication year - 1968
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1111/j.1365-2621.1968.tb01432.x
Subject(s) - chemistry , metal ions in aqueous solution , copper , absorption (acoustics) , metal , cobalt , ion , absorption spectroscopy , inorganic chemistry , magnesium , aluminium , absorption band , transition metal , materials science , optics , organic chemistry , physics , composite material , catalysis
Summary. The visible absorption spectra of twenty‐two food dyes have been plotted both in the free state and in the presence of added calcium, magnesium, aluminium, iron (II), iron (III), copper (II) and cobalt (II) ions at the pH values 3.0, 6.4, 7.4 and 12.5. The frequencies of the absorption band maxima of the free dyes are briefly discussed in relation to colour and structure. While added metal ions do not, in general, have an appreciable effect on the spectrum of the dye, the transition metal ions studied frequently bring about a shift in the characteristic frequencies of the free‐dye absorption maxima. Examples of where this effect is greatest are carmoisine in the presence of copper (II) at pH 6.4 and 7.4, and black PN in the presence of iron (II) at pH 12.5. The possibility of dye complexes affecting iron metabolism is also briefly discussed.