Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT:
Honeybush tea, also known as “South Africa’s sweetest tea”, is a herbal tea made from the
leaves and twigs of Cyclopia spp., indigenous to the fynbos biome in the Western and Eastern Cape
provinces of South Africa. The pleasant sweet aroma and taste of fermented honeybush, its low
tannin content and the absence of caffeine have led to widespread interest in the commercial
cultivation and processing of honeybush tea since the mid-1990s. Although more than 20 species of
honeybush grow in the wild, only a few species are commercially exploited for the manufacture of
tea. Currently the more prominent species are C. intermedia, C. subternata, C. genistoides, and C.
sessiliflora. The present research contributes to a comprehensive honeybush research programme
being conducted at the Agricultural Research Council (ARC) Infruitec-Nietvoorbij in South Africa.
The first phase of the present study, using C. genistoides as representative species, was aimed
at developing the necessary methodology for the analysis of extremely low concentrations of
honeybush volatiles. A high-capacity headspace sample enrichment probe was applied successfully
in conjunction with gas chromatography-mass spectrometry (GC-MS) to analyse the volatile organic
compounds present in dry or infused unfermented and fermented honeybush.
A total number of 255 volatile compounds were identified in unfermented and fermented
honeybush, the majority of which are terpenoids (138; 54%) comprising mostly terpenes, terpene
ketones, terpene alcohols and terpene ethers. Of the other compound classes, the aldehydes are the
largest group, followed by esters, hydrocarbons and ketones. The stereochemistry of the identified
compounds was determined whenever possible. This is the most comprehensive chemical
characterisation of the volatile compounds in a South African herbal plant reported to date.
A comparative study of green and fermented honeybush showed that the same compounds
are, to a large extent, present in both, albeit in different relative concentrations.
Not all of the identified honeybush volatiles are necessarily odour-active compounds
contributing to the overall typical honeybush aroma. An important aspect of this research was thus
the identification of the 46 odour-active compounds in fermented honeybush by means of gas
chromatography-olfactometry (GC-O), using detection frequency and aroma extract dilution analysis
methods. Fifteen of these compounds, mainly terpenoids, were singled out as the most intense
individual contributors to the honeybush aroma based on consideration of all the relevant GC-O data.
The odours of certain compounds, i.e. (6E,8Z)-megastigma-4,6,8-trien-3-one, (6E,8E)-megastigma-
4,6,8-trien-3-one, (7E)-megastigma-5,7,9-trien-4-one, 10-epi- -eudesmol, epi- -muurolol and epi- -
cadinol, were perceived by GC-O assessors as typically honeybush-like.
The quantitative GC-MS data of seven different Cyclopia samples (including four different
species and variants thereof) were compared with respect to all the volatile components and
particularly with respect to the odour-active compounds. Interesting variations were found in the
concentrations of certain odour-active compounds in the various samples.
The quantitative data obtained for the odour-active honeybush volatiles and data obtained from
the sensory analysis of eight Cyclopia samples (including four different species and variants thereof) were subjected to statistical analysis and interesting associations between compounds with certain
sensory aroma attributes were established.
The present study has made a major contribution to the scientific knowledge regarding one of
South Africa’s most popular indigenous herbal teas. / AFRIKAANSE OPSOMMING:
Heuningbostee, wat ook bekend staan as “Suid-Afrika se soetste tee”, word gemaak van die
blare en takkies van Cyclopia spp. wat inheems is en voorkom in die fynbosbioom van die Wes- en
Oos-Kaapprovinsies van Suid-Afrika. Die aangename soet smaak en aroma van gefermenteerde
heuningbos, die lae tannnien-inhoud en die feit dat die tee kafeïenvry is, het gelei tot belangstelling in
die kommersiële verbouing en prosessering van heuningbostee gedurende die 1990s. Meer as 20
heuningbosspesies kom in die natuur voor, maar slegs ‘n paar spesies word kommersieel verbou vir
die vervaardiging van heuningbostee waarvan C. intermedia, C. subternata, C. genistoides en C.
sessiliflora tans die belangrikste spesies is. Die navorsing maak deel uit van ‘n omvattende
heuningbos navorsingsprogram wat onder leiding staan van die Landbounavorsingsraad Infruitec-
Nietvoorbij in Suid-Afrika.
In die eerste fase van die huidige studie is die nodige analitiese metodologie ontwikkel vir die
monsterneming en analise van die vlugtige organiese verbindings wat in uiters lae konsentrasies in
heuningbos voorkom, deur van ‘n verteenwoordigende spesie, C. genistoides, gebruik te maak. ‘n
Sogenaamde “sample enrichment probe” (SEP) is ontwikkel en suksesvol in kombinasie met
gaschromatografie-massaspektrometrie (GC-MS) aangewend vir die analise van die vlugtige
verbindings aanwesig in die bodamp van sowel droë plantmateriaal as infusies van
ongefermenteerde en gefermenteerde heuningbos.
‘n Totaal van 255 vlugtige verbindings is geïdentifiseer, waarvan die meeste hoofsaaklik
terpenoïede is (138, 54%) en terpene, terpeenketone, terpeenalkohole en terpeeneters insluit. Die
ander verbindingsgroepe, waarvan die aldehiede die grootste groep is, sluit in esters,
koolwaterstowwe en ketone. Indien haalbaar, is die stereochemie van die geïdentifiseerde
verbindings ook bepaal. Hierdie studie is die mees omvattende chemiese karakterisering van die
vlugtige verbindings in ‘n Suid-Afrikaanse kruieplant wat tot dusver onderneem is.
‘n Vergelykende studie het getoon dat ongefermenteerde en gefermenteerde heuningbos tot ‘n
groot mate dieselfde verbindings, hoewel in verskillende relatiewe konsentrasies, bevat.
Nie al die geïdentifiseerde vlugtige verbindings in heuningbos is noodwendig aroma-aktiewe
verbindings wat ‘n bydrae tot die algehele tipiese heuningbosaroma lewer nie en daarom was die
identifisering van die 46 aroma-aktiewe verbindings in geferementeerde heuningbos deur gebruik te
maak van gaschromatografie-olfaktometrie (GC-O) deur middel van deteksiefrekwensie en aroma
ekstrak verdunningsanalise, ‘n belangrike aspek van die navorsing. Na oorweging van al die
tersaaklike GC-O data is 15 van hierdie verbindings, hoofsaaklik terpenoïede, uitgesonder as die
verbindings wat die belangrikste bydrae tot die heuningbosaroma lewer. Die reuke van sekere van
die verbindings, nl. (6E,8Z)-megastigma-4,6,8-triën-3-oon, (6E,8E)-megastigma-4,6,8-triën-3-oon,
(7E)-megastigma-5,7,9-triën-4-oon, 10-epi- -eudesmol, epi- -muurolol, en epi- -cadinol, is deur
sommige van die GC-O paneellede as tipies heuningbosagtig beskryf.
Die kwantitatiewe GC-MS data van sewe verskillende Cyclopia monsters (insluitende vier
verskillende spesies en variante daarvan) is vergelyk met betrekking tot al die vlugtige verbindings, asook veral met betrekking tot die aroma-aktiewe verbindings. Interessante variasies in die
konsentrasies van sekere aroma-aktiewe verbindings is in die verskillende monsters waargeneem.
Die kwantitatiewe data van die aroma-aktiewe heuningbosverbindings en data verkry uit die
sensoriese analise van agt Cyclopia monsters (insluitende vier verskillende spesies en variante
daarvan), is onderwerp aan statistiese analises waaruit interessante assosiasies tussen verbindings
met sekere sensoriese aroma-eienskappe waargeneem is.
Hierdie studie lewer ‘n groot bydrae tot die wetenskaplike kennis aangaande een van Suid-
Afrika se mees populêre inheemse kruietees.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5157 |
| Date | 12 1900 |
| Creators | Cronje, Joan Christel |
| Contributors | Le Roux, Maritha, 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 |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
Page generated in 0.0035 seconds