Czech J. Food Sci., 2004, 22(10):S109-S112 | DOI: 10.17221/10629-CJFS

Allium discoloration: the nature of onion pinking and garlic greening

R. Kubec, M. Hrbáčová, R. A Musah, J. Velíšek

¹ Department of Food Chemistry and Analysis, Institute of Chemical Technology, Prague, Czech

² Department of Chemistry, SUNY Albany, Albany, NY, USA

Precursors involved in the formation of pink and green-blue pigments during onion and garlic processing, respectively, have been studied. It has been confirmed that the formation of both pigments is of a very similar nature, with (E)-S-(1-propenyl)cysteine sulfoxide (isoalliin) serving as the primary precursor. Upon disruption of the tissue, isoalliin and other S-alk(en)ylcysteine sulfoxides are enzymatically cleaved, yielding prop-1-enylcontaining thiosulfinates [CH₃CH = CHS(O)SR; R = methyl, allyl, propyl, 1-propenyl], among others. The latter compounds subsequently react with amino acids to produce the pigments. Whereas the onion and leek-related propyl, prop-1-enyl and methyl derivatives can form pink, pink-red and magenta compounds, those containing the allyl group yield dark blue products after reacting with glycine at pH 5.0.

Keywords: Allium; garlic; onion; discoloration; pigment

Published: December 31, 2004  Show citation