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

J Agric Food Chem

Laboratory of Molecular Structure Characterization, Institute of Microbiology, v.v.i., Academy of Sciences of the Czech Republic , Vídeňská 1083, 142 20 Prague 4, Czech Republic.

Published: November 2015

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.

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http://dx.doi.org/10.1021/acs.jafc.5b04564DOI Listing

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