期刊
FOOD CHEMISTRY
卷 131, 期 3, 页码 852-861出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.foodchem.2011.09.059
关键词
Alliinase; Amino acids; Greening; Reddening; Thiosulphinates
资金
- Cooperative State Research, Education, and Extension Service, US Department of Agriculture [2009-34402-19831]
- Designing Foods for Health through the Vegetable & Fruit Improvement Center, Texas AgriLife Research
The chemical structures of pink-red pigments responsible for 'pinking' in macerated onion were tentatively elucidated using HPLC with a diode array detector and tandem mass spectrometry. All pigments were produced in conditions that approximated the natural process as closely as possible, using mixtures of onion thiosulphinates, the enzyme alliinase, and free amino acids. The isotopic distribution of protonated molecules of pink-red pigments produced from individual amino acids indicated the absence of sulphur, with the exception of pigment produced from cystine. The pigments had a basic polymethine framework containing two pyrrole rings (3,4-dimethyl-1H-pyrrole and 3,4-dimethyl-2,5-dihydro-1H-pyrrole) bridged by methines. The side chains attached to the nitrogen of the pyrrole rings were derived from the reacting amino acid. The simplest pink-red pigment, produced from glycine, was identified as 2-(2-(3-(1-(carboxymethyl)-3,4-dimethyl-1H-pyrrol-2(5H)-ylidene)prop-1-en-1-yl)-3,4-dimethyl-1H-pyrrol-1-yl)acetic acid. The pigment from alanine was identified as 2-(2-(3-(1-(carboxymethyl)-3,4-dimethyl-1H-pyrrol-2-yl)allylidene)-3,4-dimethyl-2,5-dihydro-1H-pyrrol-1-yl)propanoic acid. The chemical structures of pink-red pigments from leucine, asparagine, glutamine, tyrosine, and cystine also were determined. (C) 2011 Elsevier Ltd. All rights reserved.
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