Allium Discoloration: Color Compounds Formed during Pinking of Onion and Leek

Structures and formation pathways of compounds responsible for pink discoloration of onion and leek were studied. A procedure was developed for the isolation and purification of the color compounds from various model systems and their identification by HPLC-DAD-MS/MS. In total, structures of 15 majo...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2015-11, Vol.63 (46), p.10192-10199
Main Authors: Kubec, Roman, Urajová, Petra, Lacina, Ondřej, Hajšlová, Jana, Kuzma, Marek, Zápal, Jakub
Format: Article
Language:English
Subjects:
Chromatography, High Pressure Liquid
Color
Cysteine - analogs & derivatives
Cysteine - chemistry
Onions - chemistry
Pigments, Biological - analysis
Pigments, Biological - chemistry
Pigments, Biological - isolation & purification
Sulfinic Acids - chemistry
Tandem Mass Spectrometry
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Summary:Structures and formation pathways of compounds responsible for pink discoloration of onion and leek were studied. A procedure was developed for the isolation and purification of the color compounds from various model systems and their identification by HPLC-DAD-MS/MS. In total, structures of 15 major color compounds were tentatively determined. It was found that the pigment is a complex mixture of highly conjugated species composed of two N-substituted 3,4-dimethylpyrrole-derived rings linked by either a methine or a propenylidine bridge. These two-ring units are further modified by various C1- and C3-side chains. Experiments with isotope-labeled thiosulfinates revealed that the methine bridge and C1-side chains originate from the methyl group of methiin, whereas the C3 units are derived from the propenyl group of isoalliin.
ISSN:0021-8561
1520-5118
DOI:10.1021/acs.jafc.5b04564