Light and heat sensitivity of red cabbage extract in soft drink model systems

Citation
M. Dyrby et al., Light and heat sensitivity of red cabbage extract in soft drink model systems, FOOD CHEM, 72(4), 2001, pp. 431-437
Citations number
32
Categorie Soggetti
Food Science/Nutrition
Journal title
FOOD CHEMISTRY
ISSN journal
03088146 → ACNP
Volume
72
Issue
4
Year of publication
2001
Pages
431 - 437
Database
ISI
SICI code
0308-8146(200103)72:4<431:LAHSOR>2.0.ZU;2-A
Abstract
Anthocyanins of red cabbage (Brassica oleracea L.) display colour over a la rger range of pH-values than the majority of anthocyanins from other natura l sources, being pink at pH 3, violet at pH 5 and blue at pH 7. Using rever sed phase high-performance liquid chromatography with diode array detection , cyanidin was found to be the only anthocyanidin of red cabbage extract an d, tentatively, identified as cyanidin-3,5-diglucoside and cyanidin-3-sopho roside-5-glucoside, the latter found in various acylated forms. The apparen t quantum yield for photobleaching has been determined for red cabbage extr act at 25 degreesC in air-saturated McIlvaine buffer, using monochromatic l ight at each of the irradiation wavelengths, 313, 366, and 436 nm, in conti nuous photolysis experiments, in order to provide an objective measure for the sensitivity of this food colorant to ultraviolet and visible light. The quantum yield was found to depend on both pH and irradiation wavelength, r anging from 0.2x10(-4) mol einstein(-1) for 436 nm light at pH 7.0 to 3.7x1 0(-4) mol einstein(-1) for 366 nm light at pH 5.0. The thermal stability at pH 3.0 in McIlvaine buffer of four different anthocyanin extracts was comp ared and, for the temperature range investigated (25-80 degreesC) the degre e of stability was red cabbage > blackcurrant > grape skin > elderberry. Th e thermal stability of the same anthocyanin extracts was also compared for a non-carbonated soft drink medium of pH 3.0 yielding the same order of sta bility but with rates of degradation approximately twice as high as in buff er,, which may indicate a detrimental effect of sugar and ascorbic acid. Du e to the high thermal stability of red cabbage extract in solution, photobl eaching will be the primary destabilising factor for red cabbage anthocyani n-coloured products in display. (C) 2001 Elsevier science Ltd. All rights r eserved.