Photobleaching of astaxanthin and canthaxanthin. Quantum-yields dependence of solvent, temperature, and wavelength of irradiation in relation to packaging and storage of carotenoid pigmented salmonoids

Anne Grethe Christophersen, Huang Jun, Kevin Jørgensen, Leif H Skibsted

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The quantum yield for the photobleaching of astaxanthin (the carotenoid of wild salmonoids) and of canthaxanthin (the closely related carotenoid used as a feeding additive for farmed salmonoids) has been determined for monochromatic light at different wavelengths and in different solvents. Astaxanthin is less sensitive to light than canthaxanthin. The photobleaching is strongly wavelength dependent, and the quantum yield for astaxanthin dissolved in chloroform at 22-degrees-C is 3.2 x 10(-1) mol.Einstein -1 at 254 nm, 3.1 x 10(-2) at 313 nm, and 1.6 x 10(-6) at 436 nm, respectively. The quantum yields are less dependent on the nature of the solvent and show no simple correlation with oxygen solubility, i.e. for 366 nm excitation of astaxanthin the quantum yields are 6.1 x 10(-5) mol.Einstein-1 in acetone, 1.2 x 10(-4) in saturated vegetable oil, 1.9 x 10(-4) in chloroform, and 3.4 x 10(-4) solubilized in water, respectively. The photobleaching quantum yield provides an objective measure of the light sensitivity of the carotenoids in relation to the discolouration of carotenoid-pigmented salmonoids. The quantum yield was also found to be independent of the carotenoid concentration and, in a homogenous solution, of light intensities. For astaxanthin solubilized in water, the quantum yield increases for low light intensities. Excitation of astaxanthin solubilized in water using visible light shows that the photobleaching quantum yield is independent of temperature, while excitation at 313 nm shows an increase in the quantum yield with increasing temperatures, corresponding to an energy of activation of 28 kJ.mol-1. From the available photophysical data for beta-carotene, an upper limit of 3 x 10(-5) mol.Einstein-1 for photooxidation quantum yields for carotenoids is estimated for a limiting non-radical mechanism, providing an estimate of 10(4) for the chain length in a radical process initiated by 254 nm light.
Original languageEnglish
JournalEuropean Food Research and Technology
Volume192
Issue number5
Pages (from-to)433-439
ISSN0044-3026
Publication statusPublished - 1991
Externally publishedYes

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