Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Honeybush (Cyclopia spp.) is indigenous to South Africa and consists of more than 20 species of
which only a few are used to make a herbal tea with a unique aroma and sweet taste. The aroma of
unfermented and fermented honeybush tea differs considerably, indicating that changes take place in
the chemical composition of the aroma during the fermentation process. Using a sample enrichment
probe (SEP) and gas chromatography-mass spectrometry (GC-MS), the chemical composition of the
aroma of unfermented and fermented C. genistoides, was analyzed and the resulting aroma profiles
were compared. A total of 74 compounds were identified in the unfermented honeybush aroma,
comprising, inter alia, a large number of saturated and unsaturated alcohols, aldehydes and methyl
ketones that were found to be either absent, or present in lower relative concentrations, in the aroma
of fermented honeybush. Most of these compounds, including 6-methyl-5-hepten-2-one, identified
as one of the major constituents of unfermented honeybush, are probably responsible for its grassy,
hay-like aroma. In the aroma of fermented honeybush 70 compounds were identified, of which 36
were found to be terpenoids. These compounds are probably responsible for the pleasant sweet
aroma of the fermented honeybush. For instance, the major aroma constituent in the fermented
honeybush, α-terpineol, is known to have a delicately floral and sweet odour. Other terpenoids
occuring in significant quantities in the fermented honeybush, are linalool, cis and trans linalool
oxide, nerol, geraniol, 2,6-dimethyl-1,7-octadien-3,6-diol, hexahydrofarnecyl acetone and phytol.
These terpenoids are known to have sweet, sweet-woody en floral odours that probably contribute to
the overall sweet aroma of the fermented honeybush. In the aroma of the unfermented honeybush a
total of 25 terpenoids was identified, of which geranyl acetone, β-ionone, and dihydroactinidiolide
are the most significant, since they are present in higher relative concentrations compared to the
same terpenoids in the fermented honeybush. These three terpenoids have overall woody and even
slightly green odours which contribute to the typical aroma of the unfermented honeybush. The
terpenoids present in the aroma of unfermented and fermented honeybush belong to the following
compound classes:
• Terpenes
• Terpene alcohols
• Terpene aldehydes
• Ketoterpenes
• Terpene ethers
• Terpene lactones
Apart from the terpenoids present in the aroma of unfermented and fermented honeybush, the
following classes of compounds are also present:
• Aliphatic hydrocarbons (saturated)
• Aliphatic alcohols (saturated and unsaturated)
• Phenols
• Aliphatic aldehydes (saturated and unsaturated)
• Aliphatic ketones (saturated and unsaturated)
• Aliphatic carboxylic acids (saturated)
• Esters (methyl esters, ethyl and higher esters and aromatic esters)
• Furane compounds
• Lactones
The present research was done to compare the chemical composition of the aroma of unfermented
and fermented honeybush of one particular species, namely C. genistoides, to obtain an
understanding of the evolution and/or disappearance of volatile compounds during fermentation that
ultimately could help to identify compounds or compound types and their precursors responsible for
its unique sweet aroma.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2484 |
| Date | 03 1900 |
| Creators | Cronje, Christel |
| Contributors | Le Roux, M., Burger, B. V., University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Format | 9650463 bytes, application/pdf |
| Rights | University of Stellenbosch |
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