Thearubigins are polyphenolic oligmers which contribute to the quality of black tea: it is necessary to learn more of their origin and structure in order to understand their function, and to utilise opportunities to influence their development during processing to meet market demand. Tea samples were manufactured under controlled conditions, by methods parallel to commercial production in Malawi. Leaf handling, withering, fermentation and drying were manipulated. Conditions selected could be used in current commercial tea factories with only minor modifications. Non-volatile water-soluble components of black tea were analysed in an attempt to identify the critical points in the process. Solvent partition, adsorption chromatography or caffeine precipitation followed by size..exclusion HPLC were used to further separate the thearubigins and estimate molecular mass. Reverse-phase HPLC was also used; both methods were monitored by UV-VIS spectroscopy. Eluate was collected and portions challenged with chemical probes to identify functional groups within the oligmers. Theafulvin was shown to be heterogeneous in both chemical composition and mass. Prolonged fennentation in the presence of air promoted the development of theafulvin, caffeine-precipitable thearubigin, and hump unresolved by reverse-phase HPLC. This is the first evidence that theafulvin is a product of fermentation rather than a plant artefact. Leaf handling and fermentation conditions have a greater impact on liquor colour and perceived quality than withering or well-controlled drying. Modified dryer operating conditions preserved product composition and quality. Opportunities to manipulate product composition to meet market demand were identified.

Thesis (MSc Food Sc) (Food Science)--University of Stellenbosch, 2005. / Near infrared spectroscopy (NIRS) and UV/Vis spectrophotometric methods were investigated as rapid and/or more economical methods to quantify the major monomeric phenolic compounds, soluble solid content (SSC), total polyphenol content (TPC) and total antioxidant activity (TAA) of green rooibos and Cyclopia genistoides.

Theanine is a free, non-protein amino acid found in Camellia sinensis (tea) leaves. It is the main amino acid component in tea and contributes 1 to 2% of the dry weight of tea leaves. The content of amino acids is a key green tea quality parameter. High grade teas contain high amounts of theanine. It is responsible for the sweet, brothy umami taste of green tea. To date there is no international standard method for the analysis of theanine in tea samples. Several methods with different advantages and disadvantages have been reported but most of them are unsuitable for routine quality control analysis in commercial tea samples. In this study, a high performance liquid chromatography (HPLC) method with evaporative light scattering detection for the determination of theanine in tea samples has been developed. Chromatographic separation of theanine was achieved by reverse phase HPLC using a phenyl-hexyl column and isocratic water elution within 8 minutes. The method requires no sample derivatization and includes simple sample clean-up. Applying the same chromatographic conditions to a widely available C18 column, separation of theanine was achieved within 10 minutes. The successful application of the C18 column renders this method widely applicable. The method is linear over several orders of magnitude and the LOD are 11.53 and 10.83 μg/ml and the LOQ are 39.44 and 35.10 μg/ml for the phenyl-hexyl and C18 column, respectively. Simple but effective sample preparation and polyvinylpolypyrrolidone pre-treatment, along with the short analysis time facilitates high sample throughput (~40 samples can be prepared in an 8 hour day with overnight analysis by HPLCELSD). The method is selective, precise, accurate and practical for the quantification of theanine in tea extracts and was successfully used to determine theanine content in a variety of tea samples. The sensitivity and simplicity of this method renders it suitable for use in routine theanine analysis in quality control laboratories. Green tea, a simple refreshing beverage, has been believed to have therapeutic uses for centuries. Scientists have recognized that the wide range of physiological functions of green tea is due to the presence of catechins. An increasing body of evidence is showing that methylated forms of catechins have potent inhibitory activities to allergies. In addition to the methylated catechins, another relative novel group of catechins exists, namely digallated catechins. The medicinal value of these compounds is not yet known, but it is reasonable to speculate that the antioxidant capacity of digallated catechins will be superior to that of epigallocatechin gallate due to the 3 additional hydroxyl groups provided by the second gallic acid moiety. In this study reverse phase UPLC/ESI-MS/MS was effectively applied to investigate the presence of digallated and methylated catechins in crude tea extract. Low abundance catechins (-)-epigallocatechin-(O-3”-methyl) gallate ([M + H]+, m/z 473) and (-)-epicatechin-3-(O-3”-methyl) gallate ([M + H]+, m/z 457) were successfully detected at 31.9 and 37.5 minutes, respectively. The 2 digallated catechins investigated could not be detected, possibly due to being present at concentrations below the limit of detection. Compared to conventional HPLC/ESI-MS/MS, increased resolution and sensitivity, 80% less use of solvent and significantly reduced analysis times were observed. / Dissertation (MSc)--University of Pretoria, 2009. / Biochemistry / unrestricted

Bush tea (Athrixia phylicoides DC.) is a herbal beverage and medicinal plant indigenous to South Africa. A trial was conducted to determine the effect of micronutrients on the plant growth and quality of bush tea. The trial was laid out in a completely randomized block design with five replicates. Treatments consisted of single applications of Zinc (Zn), Copper (Cu), Boron (Bo), Iron (Fe) and Magnesium (Mg) at three levels (50ml/l, 100ml/l and 150ml/l) and a combination of all micronutrients. A control treatment with no spray was also included. Leaf analysis was conducted using Varian Liberty series II instrument. Total polyphenols were determined using the Folin Ciocalteau method and tannins were determined using Vanillin HCl method. Bush tea samples (one leaf per sample) were analysed using head space solid phase micro-extraction gas chromatography (HS-SPME-GC-MS). Results of this study demonstrated that application of micronutrients increased the total polyphenols, tannins and total flavonoids in bush tea, with most of the increase in total polyphenols (77.5-93.7 mg/g) occurring in combination B + Zn + Fe + Cu + Mg treatment, increase in tannins (87.3-99.5 mg/g) occurring in copper treatment and increase in total flavonoids (164.6-176.6 mg/g) occurring in mixture (B + Zn + Fe + Cu + Mg) treatment. Results also show a significant increase in the quality and plant growth of bush tea. Five major compounds were identified (>80% identification probability) namely alpha-pinene, beta-pinene, myrcene, beta-caryophyllene and caryophyllene oxide. Linear relationship between percentage leaf tissues and treatments levels of micronutrients in bush tea was also observed. Boron and copper treatments showed strong linear correlation with a positive relationship between treatments levels and leaf percentage. Therefore, for improved total polyphenols content in bush tea leaves, a combination of (B + Zn + Fe + Cu + Mg) is recommended. Tannin content in bush tea leaves were significantly increased at Cu50 ml/l, Cu100 ml/l and Cu150 ml/l. For improved total flavonoids content in bush tea leaves, a combination of foliar spray of (B + Zn + Fe + Cu + Mg) is recommended. The LC-MS observations from the study showed no significant qualitative difference between control and micronutrient treatments with these treatments showing similar number of peaks. There was a significant quantitative difference between control and where magnesium peaks applied at adequate rates at (50 ml/l and 100 ml/l) and combination of (B + Zn + Fe + Cu + Mg) applied at (10 ml/l and 20 ml/l) / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)

Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In this study quality control tools were developed for the rooibos industry, primarily to determine the quality of rooibos infusions. A considerable variation between samples of the same quality grade has been noted. As there are no guidelines or procedures in place to help minimise this inconsistency it was important to develop quality control tools, which could confront this problem. Both the sensory characteristics and phenolic composition of rooibos infusions were analysed in order to create and validate these quality control tools. Descriptive sensory analysis was used for the development of a targeted sensory wheel and sensory lexicon, to be used as quality control tools by the rooibos industry, and to validate the major rooibos sensory profiles. In order to ensure all possible variation was taken into account, 230 fermented rooibos samples were sourced from the Northern Cape and Western Cape areas within South Africa over a 3-year period (2011-2013). The aroma, flavour, taste and mouthfeel attributes found to associate with rooibos sensory quality were validated and assembled into a rooibos sensory wheel, which included the average intensity, as well as the percentage occurrence of each attribute. Two major characteristic sensory profiles prevalent within rooibos, namely the primary and secondary profiles, were identified. Both profiles had a sweet taste and an astringent mouthfeel, however, the primary sensory profile is predominantly made up of “rooibos-woody”, “fynbos-floral” and “honey” aroma notes, while “fruity-sweet”, “caramel” and “apricot” aroma notes are the predominant sensory attributes of the secondary profile. The predictive value of the phenolic compounds of the infusions towards the taste and mouthfeel attributes (“sweet”, “sour”, “bitter” and “astringent”) was examined using different regression analyses, namely, Pearson’s correlation, partial least squares regression (PLS) and step-wise regression. Correlations between individual phenolic compounds and the taste and mouthfeel attributes were found to be significant, but low. Although a large sample set (N = 260) spanning 5 years (2009-2013) and two production areas (Western Cape and Northern Cape, South Africa) was used, no individual phenolic compounds could be singled out as being responsible for a specific taste or mouthfeel attribute. Furthermore, no difference was found between the phenolic compositions of the infusions based on production area, a trend that was also seen for the sensory characterisation of rooibos infusions. Sorting, a rapid sensory profiling method was evaluated for its potential use as a quality control tool for the rooibos industry. Instructed sorting was shown to successfully determine rooibos sensory quality, especially based on the aroma quality of the infusions. However, determining the quality of the infusion based on flavour quality was more difficult, possibly due to the low sensory attribute intensities. Categorisation of rooibos samples based on the two major aroma profiles i.e. the primary and secondary characteristic profiles, was achieved with uninstructed sorting. The potential of using sorting as a rapid technique to determine both quality and characteristic aroma profiles, was therefore demonstrated, indicating its relevance as another quality control tool to the rooibos industry. / AFRIKAANSE OPSOMMING: Gehaltebeheer hulpmiddels is as deel van hierdie studie vir die rooibosbedryf ontwikkel, hoofsaaklik om die sensoriese kwaliteit van rooibostee te bepaal. Aansienlike verskille is tussen monsters van dieselfde gehaltegraad opgemerk, primêr omdat daar in die wyer rooibosbedryf beperkte riglyne of prosedures in plek is om kwaliteitsverskille effektief te bepaal. Dit is as belangrik geag om gehaltebeheer hulpmiddels te ontwikkel om laasgenoemde probleem aan te spreek. Spesifieke gehaltebeheer hulpmiddels is dus vir hierdie studie ontwikkel en gevalideer deur die sensoriese eienskappe en fenoliese samestelling van rooibostee te analiseer. Beskrywende sensoriese analise (BSA) is gebruik om ‘n sensoriese wiel en leksikon vir die rooibosbedryf te ontwikkel en te valideer. Om alle moontlike produkvariasie te ondervang, is 230 gefermenteerde rooibos monsters afkomstig van die Noord-Kaap en Wes-Kaap areas in Suid-Afrika oor ‘n tydperk van drie jaar (2011-2013) verkry. Die aroma, geur, smaak en mondgevoel eienskappe wat met rooibos se sensoriese kwaliteit assosieer, is bevestig en uiteindelik gebruik om die sensoriese wiel te ontwikkel. Die gemiddelde intensiteit en persentasie voorkoms van elke eienskap is in die wiel ingesluit. Twee belangrike “karakteristieke” sensoriese profiele wat met rooibos geassosieer word, is geïdentifiseer, nl. die primêre en sekondêre sensoriese profiele. Tipies van beide sensoriese profiele is ‘n kenmerkende soet smaak en vrank mondgevoel, daarenteen bestaan die primêre sensoriese profiel hoofsaaklik uit "rooibos-houtagtige", "fynbos-blomagtige" en "heuning" aromas, terwyl "vrugtige-soet", "karamel" en "appelkoos" aromas die oorheersende sensoriese eienskappe van die sekondêre profiel is. Die korrelasie tussen die fenoliese verbindings en die smaak en mondgevoel eienskappe van rooibos ("soet", "suur", "bitter" en "vrankheid") is ondersoek met behulp van verskillende tipe regressieontledings, nl. Pearson se korrelasie, gedeeltelike kleinstekwadrate regressie (PLS) en stapsgewyse regressie. Korrelasies tussen individuele fenoliese verbindings en die smaak en mondgevoel eienskappe was laag, maar steeds betekenisvol. Alhoewel die uitgebreide stel monsters (N = 260) verteenwoordigend was van vyf oesjare (2009-2013) en twee produksiegebiede (Wes-Kaap en Noord-Kaap, Suid-Afrika), kon geen individuele fenoliese verbindings uitgesonder word as betekenisvolle voorspellers van spesifieke smaak of mondgevoel eienskappe nie. Verder is daar ook geen verskil tussen die verskillende produksie-areas wat betref fenoliese samestelling gevind nie. Soortgelyke resultate is bevind vir die sensoriese karakterisering van rooibostee. Sortering, 'n vinnige sensoriese profileringsmetode, is geëvalueer vir sy potensiële gebruik as 'n gehaltebeheer hulpmiddel vir die rooibosbedryf. Gestrukteerde sortering was suksesvol om rooibos se sensoriese kwaliteit, veral die algemene aroma kwaliteit van rooibos, te bepaal. Hierdie profileringsmetode was egter nie so suksesvol om rooibos se algemene geur, smaak en mondgevoeleienskappe te bepaal nie. Hierdie tendens kan moontlik toegeskryf word aan die betekenisvolle laer intensiteite van laasgenoemde sensoriese eienskappe. Die kategorisering van die rooibos monsters op grond van hul karakteristieke primêre en sekondêre sensoriese profiele is suksesvol deur middel van ongestrukteerde sortering bepaal. In die geheel gesien is die potensiaal van die sorteringstegniek as ‘n vinnige metode om die algemene sensoriese kwaliteit, asook die karakteristieke aroma profiele van rooibos te bepaal, dus bewys. Hierdie vinnige sensoriese profileringstegniek hou dus besliste voordele in vir die rooibosbedryf as dit kom by sensoriese gehaltebeheer.