Garlic: main constituents

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Garlic contains a wealth of sulfur compounds; most important for the taste is allicin (diallyl di­sulphide oxide), which is produced enzymati­cally from alliin (S-2-propenyl-L-cysteine sulfoxide) if cells are damaged; its biological function is to repel herbi­vorous animals. Allicin is deacti­vated to diallyl di­sulphide; therefore, minced garlic changes its aroma if not used imme­diately. In the essential oil from steam distil­lation, diallyl di­sulphide (60%) is found besides diallyl tri­sulphide (20%), diallyl sulfide, ajoene and minor amounts of other di- and poly­sulphides. Sulfur com­pounds of this kind are typical for the onion family; see also bear’s garlic, onion and chives.

In other bo­tanical groups, garlic scent caused by similar sulphur chemism is un­com­mon. While the cab­bage family is rich in species ac­cumu­lating sulphur com­pounds (e. g., they cause the typical flavour of cress, mustard and the various cab­bage types), true garlic aroma is rarely found; an example for such a plant is hedge garlic (Alliaria petiolata). Asafetida is an important sulphur-containing spice that replaces garlic is some South Asian cuisines. Lastly, the exotic garlic vine (Cydista aequi­noctialis syn. Mansoa alliacea) should be mentioned: This South American creeper boasts of beautiful flowers and strikingly garlic-scented Leaves.

source: www.gernot-katzers-spice-pages.com