Flavor Precursors and Amino Acids Involved in Blue-Green Pigment Formation in Crushed Garlic Cloves
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abstract
Blue-green pigments are occasionally formed in macerated garlic cloves over time, which creates some marketing problems in minced garlic products. In this study, we investigated garlic discoloration by using mixtures of garlic and onion juices, as well as using isolated flavor precursors, trans-(+)-S-1- propenyl-L-cysteine sulfoxide (1-PeCSO, isoalliin) from onion and (+)-S-2-propenyl (or allyl)-(2-PeCSO, alliin) from garlic, respectively. Pigment formation was associated with an alliinase activity and the increased levels of flavor precursors, particularly1-PeCSO, and several amino acids. However, cysteine and proline did not result in coloration. Upon maceration of the tissue, 1-PeCSO and 2-PeCSO were enzymatically cleaved and yielded 1-and 2-propenyl-thiosulfinates. Subsequently, they reacted with amino acids and produced the pigments. Vivid-blue color was successfully produced by using a reaction system comprising only 1-PeCSO and 2-PeCSO, purified alliinase, and glycine. While pink pigments were generated from 1-PeCSO, yellow pigments produced from 2-PeCSO in a reaction of alliinase and glycine.
