Changes in the chlorophyll and carotenoid content and composition of ground thyme leaves as a function of supercritical carbon dioxide and subcritical propane extraction

S. Hamdan, H. G. Daood

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

This work was conducted to study the changes in the content and composition of chlorophylls and carotenoids in ground thyme leaves as a function of supercritical carbon dioxide and sub-critical propane extraction. the results indicated that the maximum oleoresin yield could be obtained with supercritical carbon dioxide at 400 bar and 35 or 55°C and sub-critical propane at 50 bar. Pigment solvating capacity of supercritical carbon dioxide increased with the increase of extraction pressure. Substantial variation was noticed in pigment composition between raw material, oleoresin and residues (powders after extraction). Chlorophyll b, chlorophyll a and the Mg-free derivatives were the dominant pigments in the raw material with other derivatives being minor constituents. After extraction with supercritical carbon dioxide at 35°C and pressures higher than 200 bar, epimerisation and oxidation of chlorophylls lead to marked accumulation of artefacts in the residues. The content of oxidized chlorophylls was increased proportionally to the increase of the extraction pressure. The brownish green coloured-oleoresins contained only pheophytins indicating that rapid substitution of Mg with hydrogen atoms on the molecules takes place during extraction of such pigment by supercritical carbon dioxide and sub-critical propane. The marked conversion of chlorophyll to pheophytins was found in oleoresin extracted by supercritical fluid extraction at 55°C and 100 bar.

Original languageEnglish
Pages (from-to)8-18
Number of pages11
JournalActa Alimentaria
Volume40
Issue number1
DOIs
Publication statusPublished - Mar 1 2011

Keywords

  • carotenoid
  • chlorophyll
  • liquid chromatography
  • supercritical fluid extraction
  • thyme

ASJC Scopus subject areas

  • Food Science

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