Cysteine reacts to form blue–green pigments with thiosulfinates obtained from garlic (Allium sativum L.)

•Cysteine was found to form pigments with thiosulfinates obtained from garlic.•Cysteine forms disulphide-type condensation products with thiosulfinates.•The pigment-forming reaction is between residual thiosulfinates with disulphide products.•The molar concentration ratio of cysteine to total thiosu...

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Bibliographic Details
Published in:Food chemistry 2014-01, Vol.142, p.217-219
Main Authors: Shin, Young Keum, Kyung, Kyu Hang
Format: Article
Language:English
Subjects:
Biological and medical sciences
Cysteine
Cysteine - chemistry
Food toxicology
Garlic
Garlic - chemistry
Green pigmentation
Medical sciences
Pigments, Biological - chemistry
Plant Extracts - chemistry
S-alk(en)yl mercaptocysteines
SAMC
Thiosulfinates
Thiosulfonic Acids - chemistry
Toxicology
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Summary:•Cysteine was found to form pigments with thiosulfinates obtained from garlic.•Cysteine forms disulphide-type condensation products with thiosulfinates.•The pigment-forming reaction is between residual thiosulfinates with disulphide products.•The molar concentration ratio of cysteine to total thiosulfinates should be smaller than 2 to 1 to form pigments. Cysteine was found to form pigments with garlic thiosulfinates in this investigation, in contrast to previous reports. Pigments were formed only when the molar concentration ratios of cysteine to total thiosulfinates were smaller than 2:1. Cysteine does not form pigments with thiosulfinates in the same manner as other pigment-forming amino compounds because it has a sulfhydryl (SH) group. A colour reaction of cysteine with thiosulfinates is proposed where colourless disulphide-type S-alk(en)yl mercaptocysteines (SAMCs) are formed first by the SH-involved reaction between cysteine and thiosulfinates, and then SAMCs react with residual thiosulfinates to form pigments. When the cysteine to total thiosulfinate molar concentration ratio was 2:1 or greater, total thiosulfinates were consumed to form SAMCs without leaving any thiosulfinates remaining available for the following colour reactions.
ISSN:0308-8146
1873-7072
DOI:10.1016/j.foodchem.2013.07.057