Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / The rapid expansion of the world wine industry has increased the pressure on wine producers to produce high quality, distinguishable wines. The use of sensory evaluation alone as a tool to distinguish between wines is limited by its subjective nature. Chemical characterisation using analytical methods and data analysis techniques are increasingly being used in conjunction with sensory analysis for comprehensive profiling of wine. Analytical chemistry and chemometric techniques are important and inextricable parts of the chemical characterisation of wine. Through this process insight into the inherent composition of wines, be it in a general sense or related to a particular wine category is gained. Data generated during chemical characterisation are typically compiled into electronic databases. The application of such information towards wine quality control includes the establishment of industry benchmarks and authentication. The current project is part of The South African Young Wine Aroma Project, a long term research initiative funded by the South African Wine Industry with the ultimate aim to establish a comprehensive, up-to-date, database of the volatile composition of young wines. The data generated during this thesis represent the first contribution towards realising this ambition. Three clearly defined aims were set for this project, the first of which is the chemical characterisation of South African young wines in terms of selected volatile and non-volatile compounds and Fourier transform infrared spectra, with particular focus on the volatile composition. FTMIR spectra are information rich and non-specific instrumental signals that could provide invaluable information of the inherent composition of the wines. The second aim is the evaluation of the analytical methods used to generate the data and in the last instance, the optimisation of FTMIR spectroscopy for rapid quantification of major wine parameters and volatile compounds. The concentrations of 27 volatile compounds in South African young wines were determined by gas chromatography coupled to flame ionisation detection (GC-FID) using liquid-liquid extraction of the analytes. Wine samples of the 2005 and 2006 vintages produced from six of the most important cultivars in the South African wine industry, namely Sauvignon blanc, Chardonnay, Pinotage, Cabernet Sauvignon, Merlot and Shiraz were used. The producing cellars were from four major South African wine producing regions, namely Stellenbosch, Paarl, Robertson and Worcester. The data captured made a significant contribution to the establishment of the Aroma Project Database. Univariate statistics showed wide variations in the chemical composition of the wines. Red wines were generally characterised by high levels of higher alcohols and white wines by high levels of esters. Most of the differences between vintages were cultivar dependent and phenological differences between cultivars were suggested as a possible cause. Fusel alcohols, iso-acids and esters of fusel alcohols were particularly responsible for differences between red wines. A combination of fatty acids and higher alcohols were responsible for differences between production regions. However, using univariate statistics alone was limited in identifying characteristic features of the chemical composition of the wines. In order to explore the correlations between the volatile components, FTMIR spectra and nonvolatile components the data were further investigated with multivariate data analysis. Principal component analysis was successfully employed to distinguish between wines of different vintages and cultivars. The role of the volatile composition was more influential in the separation of vintage and red wine cultivar groupings than the non-volatile components or the FTMIR spectra. Almost all the individual volatile components contributed to the separation between the vintages and cultivars, thereby highlighting the multivariate nature required to establish the distinguishing features pertaining to each of these categories. The FTMIR spectra and the non-volatile components were more important than the volatile components to characterise the differences between the white cultivars. It was not surprising that both the volatile components and the FTMIR spectra were needed to distinguish between both red and white cultivars simultaneously. It was of interest the full spectrum, including all wavenumbers were required for a powerful classification model. This finding supports the initial expectation that the non-selective but information rich signal captured in the FTMIR spectra is indispensable. No distinction could be made between the production regions, which was not surprising since the wines used in this study was not of guaranteed origin. Furthermore, no clear correlation could be established between the chemical composition or the FTMIR spectra and the quality ratings of the wines. Limitations in the dataset were pointed out that must be taken into account during further investigations in the future. The liquid-liquid extraction method used during the analysis of the volatile components was evaluated for precision, accuracy and robustness. Generally good precision and accuracy were observed. There were slight indications of inconsistencies in the recoveries of analytes between the red and white wine matrices. Certain parameters of the protocol, namely sample volume, solvent volume, sonication temperature and sonication time, were identified as factors that had a major influence on quantification. The results obtained in this study made a major contribution towards establishing this technique for routine GC-FID analysis in our environment. Due to the high sample throughput in wine laboratories, the use of rapid quantitative analytical methods such as FTMIR spectroscopy is becoming increasingly important. Enzymatic-linked spectrophotometric assays and high performance liquid chromatography (HPLC) methods were evaluated for their suitability to serve as reference methods for optimising and establishing FTMIR calibrations for glucose, fructose, malic acid, lactic acid and glycerol. Pigmented and phenolic compounds were identified as sources of interference in the determination of organic acids in red wines with both enzymatic assays and HPLC. The use of fining treatments for the decolourisation of red wine samples was investigated. Activated charcoal was more efficient in terms of colour removal than polyvinyl polypyrrolidone (PVPP), but neither were compatible with the specific enzymatic method used in this study. Solid phase extraction (SPE), a method commonly used during sample clean-up prior to HPLC analysis of organic acids in wine, and PVPP fining were evaluated as sample preparation methods for HPLC analysis to optimise the quantification of organic acids in red wine. Four different types of SPE cartridges were evaluated and the SPE method was optimised in order to recover the maximum amount of organic acids. However, low recoveries, in some instance less than 50%, for the organic acids in wine were reported for the optimised SPE method. In this respect one was the worst. On average, excellent recoveries were observed for the organic acids using the PVPP method that were in excess of 90%. This method therefore provides a very valuable and simple alternative to SPE for sample-cleanup prior to HPLC analysis. One aspect that still needs to be investigated is the reproducibility of the method that should still be optimised. In general, enzymatic analysis was more suitable for the determination of glucose and fructose, while HPLC analysis were more suitable for the quantification of organic acids. Efficient glycerol quantification was observed with both enzymatic and HPLC analysis, although a lower measurement error was observed during the HPLC analysis. Apart from reliable reference methods, successful FTMIR calibrations also rely on the variability present in the reference sample set. The reference sample set used to establish FTMIR calibrations must ideally be representative of the samples that will be analysed in the future. Commercial, or so-called global, FTMIR calibrations for the determination of important wine parameters were evaluated for their compatibility to a South African young wine matrix. The prediction pH, titratable acidity, malic acid, glucose, fructose, ethanol and glycerol could be improved by establishing a brand new FTMIR calibration, thereby clearly indicating that the South African young wine matrices were significantly different from the samples of European origin that were used to establish the commercial calibrations. New preliminary calibration models were established for a young wine sample matrix and were validated using independent test sets. On average the prediction errors were considered sufficient for at least screening purposes. The effect of wavenumber selection was evaluated. Relatively successful models could be established for all the compounds except glucose. Wavenumber selection had an influence on the efficiency of the calibration models. Some models were more effective using a small amount of highly correlated wavenumbers, while others were more effective using larger wavenumber regions. Preliminary FTMIR calibration models for the screening of volatile compound groups in young wines were evaluated. Compound groups were compiled based on chemical similarity and flavour similarity. Good linearity were observed for the “total alcohol”, “total fatty acids”, “esters” models while an interesting polynomial trend was observed for the “total esters” model. Relatively high prediction errors indicated the possibility of spectral interferences, but the models were nevertheless considered suitable for screening purposes. These findings are a valuable contribution to our environment where fermentation flavour profiles must often be examined. The important role sound and validated analytical methods to generate high quality analytical data, and the subsequent application of chemometric techniques to model the data for the purpose of wine characterisation has been thoroughly explored in this study. After a critical evaluation of the analytical methods used in this study, various statistical methods were used to uncover the chemical composition of South African young wines. The use of multivariate data analysis has revealed some limitations in the dataset and therefore it must be said that wine characterisation is not just reliant on sophisticated analytical chemistry and advanced data analytical techniques, but also on high quality sample sets.

Thesis (MBA)--Stellenbosch University, 2005. / Some digitised pages may appear illegible due to the condition of the original hard copy / ENGLISH ABSTRACT: The international surplus of wine and the strong Rand resulted in tremendous pressure on wine organizations to stay relevant and profitable. The biggest challenge for South African wine organizations are to keep a market oriented focus and manage the value chain costeffectively. This study was undertaken to investigate the structures of value chains used by South African export organizations as well as the way that these organizations function in this environment. To succeed in this goal questionnaires were sent to South African export organizations. Information was analyzed to investigate the positioning and trading terms that were generally used. The structure of value chains was determined as well as the participation of export organizations in demand chains. Data was analyzed to determine if the type of organization and the volume of export had an influence on the positioning of the organization, trading terms and the structure of the value chain. Most export organizations, exported less than 5 000 cases of wine each year and could be classified as small and medium enterprises. The type of organization had an influence on the payment terms as well as the positioning of the products in the market. The country of import mainly influenced the structure of the value chain. Ordering systems were not ideally suited to provide in the changing demand of consumers and a lack in the use of information technology to manage the value chain was apparent. A significant number of organizations were not actively involved in stimulating the consumer to buy their products. Therefore South African wine export organizations are still highly fragmented and do not succeed in managing the value chain as an integrated system. Improved market research should be done before the positioning of products with the focus on profit margins instead of price segments. Information technology should be utilized to reach higher service levels in the value chain and contribute in exceeding the buyer's expectations. / AFRIKAANSE OPSOMMING: Die huidige ooraanbod van wyn op die wêreldmark, tesame met 'n sterk rand, plaas wynprodusente onder geweldige druk om winsgewend en relevant te bly. Die grootste uitdagings vir Suid-Afrikaanse wynondernemings is om waardekettings markgefokus te kry en koste effektief te bestuur. Hierdie studie is onderneem om ondersoek in te stel na die waardekettingstrukture wat gewild is by Suid-Afrikaanse uitvoerondernemings en die wyse waarop die ondernemings daarin funksioneer. Om in hierdie doel te slaag is vraelyste na Suid-Afrikaanse uitvoerondernemings gestuur. Die inligting is verwerk om die posisionering en handelsterme wat ondernemings gebruik te ondersoek. Die struktuur van waardekettings wat na die uitvoerbestemmings gebruik word is bepaal asook die betrokkenheid van uitvoerondernemings by vraagkettings. Data is so ge-orden om te bepaal of die tipe onderneming en die volume botteluitvoere 'n invloed het op die posisionering, handelsterme en die struktuur van waardekettings. Die meeste uitvoerondernemings voer minder as 5 000 kiste per jaar uit en kan as klein en medium organisasies geklassifiseer word. Die tipe onderneming het 'n invloed gehad op betalingsterme wat beding word asook op die pryssegmente waarin wyne geposisioneer word. Die struktuur van waardekettings is hoofsaaklik beïnvloed deur die land waarheen uitgevoer word. Bestel- en versendingsisteme word nie optimaal bestuur nie en die aanwending van inligtingstegnologie om die waardeketting te bestuur kry nie baie aandag nie. Heelwat ondernemings was ook nie aktief betrokke om die verbruiker te stimuleer om sy produkte te koop nie. Suid-Afrikaanse uitvoerondernemings is dus nog baie gefragmenteerd en slaag nie daarin om die waardeketting as 'n geïntegreerde proses te bestuur nie. Beter marknavorsing behoort gedoen te word wanneer wyne posisioneer word met die fokus op winsmarges eerder as pryssegmente. Die beskibare inligtingstegnologie behoort aangewend te word om hoër diensvlakke in die waardeketting te handhaaf en so die verbruiker se verwagtinge te oortref.

Thesis (MBA (Business Management))--University of Stellenbosch, 2010.

Thesis (MBA)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The wine industry in South Africa has the potential to produce wine of world-class quality, but simultaneously large volumes of inferior quality wine are produced annually and sold in the market in cheap, low-quality packaging, making up the bottom end of the alcoholic beverage market. The study investigated the South African wine industry to determine where the industry is headed. The document focussed on inexpensive wine that is sold in cheap packaging to determine who drinks it and what the effect is on the wine industry. The methodology followed was to perform a literature study of the current situation of the South African wine industry. Personal interviews were conducted with members of wineries and companies to determine if the sales of foil bags influenced the sales on their products. The study found that the packaging, in which the inexpensive wine is sold is not the problem, but rather the quality of the wine that goes into the cheap packaging. The banning of wine sold in foil bags from the market in July 2005 shows a commitment from the industry to improve the image of the industry. It will, however, not solve the social problem of alcohol abuse in South Africa, as the profile of the inexpensive wine drinker indicated that if cheap wine is not available, they would change to any other form of cheap alcohol that is available. It is recommended that the quality of the products sold in cheap packaging must be improved. To improve the quality of the product, quality standards must be put into place in the industry that suppliers must adhere to. Policing in the industry needs to be improved to ensure that everybody adheres to the regulations. The industry must help with policing by mobilising industry resources. / AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse wynindustrie het die potensiaal om wyn van wêreldklas gehalte te produseer. Tesame hiermee word wyn van lae kwaliteit jaarliks geproduseer wat in goedkoop, lae kwaliteit verpakkings in die mark verkoop word. Dit maak die laagste deel van die alkoholiese mark uit. Die navorsing het gekyk na waar die Suid-Afrikaanse wyn industrie heen op pad is. Die dokument het gefokus op die goedkoop wyn wat verkoop word in goedkoop verpakkings, om te bepaal wie dit drink en wat die effek daarvan op die mark is. Die metodologie wat gevolg is, was om 'n literatuur studie te doen van die huidige situasie in die Suid-Afrikaanse wynindustrie. Persoonlike onderhoude met lede van kelders en maatskappye is gedoen om te bepaal of die verkope van goedkoop wyn in goedkoop verpakkings enige invloed het op hulle markte. Die studie het gevind dat die verpakkings waarin die goedkoop wyn verkoop word nie soseer die probleem is nie, maar eerder die kwaliteit van die wyn wat in die goedkoop verpakking gebruik word. Die verbod op die verkope van wyn in papsakke vanaf Julie 2005 wys die verbintenis van die industrie om die beeld van die industrie te verbeter. Dit sal egter nie die sosiale probleem in Suid-Afrika oplos nie, aangesien die profiel van die goedkoop wyndrinker aandui dat wanneer goedkoop wyn nie beskikbaar is nie, hulle enige ander vorm van goedkoop alkohol sal drink wat wel beskikbaar is. Dit word aanbeveel dat die kwaliteit van die produk wat in goedkoop verpakkings verkoop word, verbeter word. Om die kwaliteit van die produk te verbeter moet daar kwaliteitstandaarde in plek wees waaraan die verskaffers moet voldoen. Polisiëring in die industrie moet verbeter word om te verseker almal aan die regulasies voldoen. Die industrie moet help met polisiëring deur die mobilisering van industrie hulpbronne.

MScAgric / ENGLISH ABSTRACT: The Little Karoo region of South Africa stretches from Montagu in the west, through Barrydale on the Langeberg Mountain, towards Ladismith, Calitzdorp, Oudtshoorn and De Rust in the east, with the Swartberg mountain range in the north. The Wine of Origin district of Calitzdorp is a small, demarcated area around Calitzdorp in the Little Karoo, surrounded by the Rooiberg, Swartberg and Kleinberg mountains. With a mean February temperature (MFT) of 23.7ºC and a low annual rainfall of 233 mm, the district of Calitzdorp has a similar climate to that of the Douro Demarcated Region (DDR). The MFT is comparable to the DDR mean July temperature, and it seems that the Douro Superior sub-region to the east of the DDR has a mean July temperature of higher than 25°C. In the Cima Corgo sub-region (in the centre of the DDR), and the Baixo Cargo sub-region, the mean July temperatures are ±25°C and ±22°C respectively. Annual rainfall in the DDR is much higher, with Baixo Cargo recording 1 018 mm, Cima Corgo recording 658 mm and Douro Superior in the east recording only 437 mm. Touriga Naçional is one of the highest quality Portuguese red grape varieties. It produces high-quality port-style wine as well as table wines. Excellent quality Touriga Naçional wines have a dark black/purple colour, good extract, high, elegant tannin content and intense aromas, with typical plum, raisin, wild fruit, mulberry, “fynbos” and cherry aromas. The most suitable terroir for Touriga Naçional in the DDR has been found to be on sites that restrain the natural vigour of the grapevine. Soils with moderate to low water-holding capacity, in association with low rainfall, result in water deficits during the growing season and are considered optimal to restrict growth vigour. A steep, northern middle slope is ideal in the southern hemisphere for high temperatures and sunlight interception. Warm temperatures (25 to 30 °C) during the day and cooler temperatures during the night are optimal for photosynthesis and colour development. In order to study factors affecting the quality of Touriga Naçional in Calitzdorp, two Vitis vinifera L. cv. Touriga Naçional commercial vineyards in the Calitzdorp district were selected. Each vineyard was divided into two separate management blocks based on their empirically determined quality of production. Two crop-reduction treatments, the standard 50% crop reduction (which was considered to be the control) and a further less drastic treatment of 25% crop reduction, were applied. Significant differences were found in viticultural performance between the two adjacent Touriga Naçional management blocks in each vineyard, especially with respect to vigour. The upper management blocks, which provided grapes for reserve-quality port-style wines, experienced a higher water deficit due to the moderate soil water-holding capacity and higher temperatures in comparison to the lower sites. The higher water deficits had a restraining effect on the Touriga Naçional vines, and therefore the upper sites had lower vigour, which contributed to better quality of both the wine and port-style wine, and this could be recognised sensorially. However, it was not reflected in the chemical analytical results. Crop load also appeared to have an effect on the Touriga Naçional grapevines, but this appeared to be dependent on the management block. The 50% crop reduction had a significant positive effect on the sensory analyses, but did not significantly affect the chemical analyses. Calitzdorp terroir has a similar effect on Touriga Naçional compared to the DDR terroir, and that is why Calitzdorp can produce good table and port-style wines from Touriga Naçional. / AFRIKAANSE OPSOMMING: Die Klein Karoo-streek in Suid Afrika strek vanaf Montagu in die weste, deur Barrydale teen die Langeberg, na Ladismith, Calitzdorp, Oudtshoorn en De Rust in die ooste, met die Swartberg in die noorde. Die distrik van Calitzdorp is ‘n klein area rondom Calitzdorp, in die Klein Karoo, wat deur die Rooiberg, Swartberg en Kleinberg omring is. Calitzdorp het ‘n gemiddelde Februarie-temperatuur (GFT) van 23.7°C en ‘n lae jaarlikse reënval van 223 mm, wat soortgelyk is aan die klimaat van die Douro Vallei in Portugal. Die Douro Vallei se gemiddelde Julie-temperatuur (GJT) in vergelyking met die GFT van Calitzdorp is hoër, met temperature van meer as 25°C in die substreek Douro Superior. Vir die substreke Cima Cargo en Baixo Cargo is die GJT ±25°C en ±22°C onderskeidelik. Die jaarlikse reënval is ook hoër by Baixo Cargo, met 1 018 mm, Cima Cargo met 658 mm en Douro Superior met slegs 437 mm. Touriga Naçional is een van die beste Portugese rooi kultivars wat hoëkwaliteit tafel- en portwyne produseer. ‘n Tipiese hoëkwaliteit Touriga Naçional-wyn het ‘n swartpers kleur, hoë ekstrak, hoë elegante tanniene en intense aromatiese geure wat tipiese pruim, rosyne, wilde vrugte, moerbei, fynbos en kersie aromas insluit. Die geskikste terroir vir Touriga Naçional is op swak gronde wat die natuurlike groeikrag van die wingerdstok strem. Gronde met matige tot lae grondwaterhouvermoë tesame met lae reënval veroorsaak ‘n waterstremming in die wingerdstok gedurende die groeiseisoen en word as optimaal beskou omdat dit beheersde groei veroorsaak. In die suidelike halfrond word relatief steil, noordelike middelhange as ideaal beskou vir hoë temperature en maksimale sonligonderskepping. Gepaardgaande hiermee is die interne dreinasie verantwoordelik vir vinniger uitdroging van die grond. Hoë temperature (25 tot 30°C) gedurende die dag en koue nagte is optimaal vir fotosintese en kleurontwikkeling. Twee Vitis vinifera L. cv. Touriga Naçional kommersiële wingerde in die Calitzdorp-distrik is geselekteer en in twee afsonderlike bewerkingsblokke verdeel, gebaseer op kwaliteitsverskille. In elke blok was die verdeling van so ‘n aard dat daar ‘n hoërliggende helfte en ‘n laerliggende helfte was. Twee trosverminderingsbehandelings, nl. 50% (kontrole) en 25%, gebaseer op trosgetalle, is toegepas. By elkeen van die wingerde was daar betekenisvolle groeiverskille tussen die twee aangrensende helftes. Die boonste helftes (of gedeeltes) het minder gegroei a.g.v. ‘n hoër waterstremming sowel as hoër temperatuur as die laer helftes. Dit het geblyk om ‘n positiewe invloed op die kwaliteit van beide die tafel- en portwyne uit te oefen. Troslading het ook ‘n effek op die Touriga Naçional-wingerde gehad, maar dit blyk of dit blok-afhanklik is. Die 50% trosverminderingsbehandeling het ‘n beduidende positiewe verskil in die sensoriese analises gemaak, maar nie ‘n beduidende verskil in die chemiese analises van die wyne nie. Calitzdorp se terroir het ‘n soortgelyke effek op Touriga Naçional as dié van die DDR terroir en daarom kan Calitzdorp soortgelyke goeie tafel- en portwyne van Touriga Naçional produseer.

Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The varietal character of Sauvignon blanc wine is mostly defined by the balance between tropical and green vegetative flavour nuances. Grape derived methoxypyrazines are the main aroma contributors towards green vegetative flavours. Methoxypyrazines are heat and light sensitive. Due to warm climatic conditions in South Africa, methoxypyrazine levels decrease during grape ripening. The addition of food flavourings to Sauvignon blanc wine, a practice known as spiking, has occurred in the past to improve the green character of the wines. Adding flavourings to wine and selling the wine as natural certified wine is illegal in South Africa. Currently, adulterated Sauvignon blanc wines are identified using gas chromatography–mass spectrometry (GC-MS) and liquid chromatography–mass spectrometry (LC-MS) methods to quantify methoxypyrazines and compare levels to an established database. Although of high sensitivity, GC-MS and LCMS methods are costly and time consuming, therefore not optimal for routine screening of wines. Hence the need for the development of a fast and cost effective method for routine screening of large amounts of wines to identify adulteration. Small scale vinification practices were used to prepare experimental Sauvignon blanc wine. Flavourings were added to Sauvignon blanc grape juice before fermentation, during the preparation of experimental spiked wines. Control wines, containing no flavouring, were also prepared. Commercial wines were spiked after fermentation and bottling. Each wine was only spiked with a single flavouring. The flavourings added were the juice of homogenised fresh green peppers and commercially available flavourings for wine. The following commercial flavourings were used: green pepper, asparagus, grassy and tropical. The above mentioned wines were analyzed using Fourier transform infrared (FT-IR) spectroscopy, GC-MS, LC-MS and descriptive sensory analysis. The FT-IR techniques used were Fourier transform mid infrared (FT-MIR) transmission, FT-MIR attenuated reflection and Fourier transform near infrared (FT-NIR) reflection spectroscopy. The data was interpreted using the following multivariate statistical techniques: principal component analysis (PCA), partial least squares discrimination (PLS-D) and conformity testing. Multivariate models constructed from FT-MIR and FT-NIR data were able to discriminate between spiked and control wines. Sensory analysis results clearly showed differences between non-spiked wines and spiked wines with 3-isobutyl-2-methoxypyrazine concentrations 10 times higher than naturally occurring in wine. Differences between control and spiked wines with concentrations of 3-isobutyl-2-methoxypyrazine similar to concentrations naturally occurring in wines could not be detected to prove adulteration conducting sensory analysis. However, differences between control and spiked wines with levels of 3-isobutyl-2-methoxypyrazine similar to levels naturally occurring in wines could be detected using FT-IR data in conjunction with multivariate statistics. This study showed that, FT-IR spectroscopy in conjunction with multivariate statistical methods can be a possibility for the screening and identification of wines suspected of adulteration in terms of added flavourings. Descriptive sensory analysis also proved to be a potentially useful tool. However screening and training of potential panel members are time consuming. / AFRIKAANSE OPSOMMING: Die variëteitskarakter van Sauvignon blanc wyn word grotendeels gedefinieer deur die balans tussen tropiese en groen vegetatiewe aromas. Metoksipirasiene is die hoof aroma verbindings wat verantwoordelik is vir groen vegetatiewe aromas. Metoksipirasien is hitte- en ligsensitief. Warm klimaatsomstandighede in Suid-Afrika het tot gevolg dat metoksipirasien konsentrasies daal tydens druif rypwording. Sauvignon blanc wyne is in die verlede vervals deur middel van die byvoeging van vars groen soetrissies om die groen vegetatiewe karaktereienskappe van die wyne te bevorder. Die byvoeging van geurmiddels of plantekstrakte by wyn en verkoop van daardie wyn as gesertifiseerde natuurlike wyn is onwettig in Suid-Afrika. Tans word vervalsde wyne met behulp van gaschromatografie-massaspektrometrie (GC-MS) en vloeistofchromatografie-massaspektrometrie (LC-MS) opgespoor. Kwantifisering van metoksiepirasien konsentrasies in wyne en druiwesappe word vergelyk met konsentrasies in ‘n bestaande databasis. Alhoewel GC-MS en LC-MS hoë sensitiwiteitsmetodes is, is dit duur en tydrowende metodes, dus nie optimaal vir roetine sifting nie. Dus word ‘n koste- en tydseffektiewe roetine metode benodig om vervalsing van wyne op te spoor. Eksperimentele wyne is op klein skaal berei. Geurmiddels is voor fermentasie by die druiwesap gevoeg. Kontrole wyne waarby geen geurmiddels gevoeg is nie, is ook berei. Kommersiële wyne is gegeur na fermentasie en bottelering. Elke wyn is met ‘n enkele geurmiddel gegeur. Gehomogeniseerde vars groen soetrissie asook kommersieel beskikbare geursels vir wyn is gebruik. Die volgende kommersiële geursels is gebruik: groen soetrissie, aspersie, gras en tropiese geursel. Die volgende analitiese tegnieke is gebruik vir analisering van bogenoemde wyne: Fourier transformasie infrarooi (FT-IR) spektroskopie, GC-MS, LC-MS en beskrywende sensoriese analise. Die spesifieke FT-IR tegnieke wat gebruik is, is: Fourier transformasie mid-infrarooi (FT-MIR) transmissie, FT-MIR verswakte weerskaatsing en Fourier transformasie naby-infrarooi (FT-NIR) reflektansie. Die volgende multiveranderlike statistiese tegnieke is gebruik ter interpretasie van data: hoof komponent analise (PCA), parsiële kleinste kwadraat diskriminant analise (PLS-D) en gelykvormigheidstoetsing. Multiveranderlike modelle, bereken met behulp van FT-MIR en FT-NIR data, kon diskrimineer tussen gegeurde en kontrole wyne. Resultate wat verkry is tydens sensoriese analises het duidelike verskille uitgewys tussen gegeurde en kontrole wyne met betrekking tot 3-isobutiel-2- metoksipirasien konsetrasies waar 3-isobutiel-2-metoksipirasien konsentrasies 10 keer hoër was as wat natuurlik voorkom in wyn. Geen beduidende verskille kon waargeneem word in gevalle waar wyne vervals is met laer konsentrasies van geurmiddels deur sensoriese data te ontleed nie. Nietemin, statisitiese verskille tussen kontrole en vervalsde wyne kon waargeneem word vir lae-konsentrasie-geurmiddel vervalsde wyne deur FT-IR data met behulp van multiveranderlike statisitiese metodes te ontleed. Hierdie studie het gewys dat FT-IR in kombinasie met multiveranderlike statistiese tegnieke spesifiek hoof komponent analise (PCA) en parsiële kleinste kwadraat diskriminant analise (PLS-D) asook gelykvormigheidstoetsing bruikbare tegnieke is om te onderskei tussen kontrole (egte natuurlike) en vervalsde wyne ten opsigte van die byvoeging van geurmiddels. Beskrywende sensoriese analise kan ook nuttig gebruik word, alhoewel keuring en opleiding van paneellede tydrowend is.

Thesis (MScAgric)--Stellenbosch University, 1974. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (M. Sc.Voedselwet.)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Phenolic compounds in wine, due to their antioxidant activity, are reportedly responsible for the health-promoting properties of wines. The effect of cultivar and in-bottle ageing on the antioxidant activity of South African wines in different types of antioxidant assays was, therefore, investigated. The antioxidant activity of commercial South African red (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) and white (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) cultivar wines was compared using the 2,2’-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS·+) scavenging, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) scavenging and microsomal lipid peroxidation (MLP) assays. The red wines was more effective than the white wines on an “as-is” and an equal total phenol content. The total antioxidant activity (TAAABTS and TAADPPH) of Ruby Cabernet was the lowest of the red wines, but the antioxidant potency (APABTS and APDPPH) of red wine phenolic fractions did not differ (P ³ 0.05). Ruby Cabernet and Pinotage were the least effective inhibitors of MLP, while Merlot was the most effective of the red wines. Pinotage phenolic fractions had lower (P < 0.05) APMLP than that of other red wines. Of the white wines, Chardonnay and Chenin blanc had the highest and lowest effectivity respectively according to all antioxidant parameters. Ascorbic acid present in some wines increased and decreased their TAA and % MLP inhibition respectively. TAA and % MLP inhibition correlated well (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavanol content of red wines and tartaric acid ester content of white wines. The % MLP inhibition also correlated well with flavanol content of white wines. No correlation (P > 0.01) was obtained between TAA or % MLP inhibition and monomeric anthocyanin content of red wines. In the deoxyribose assay, red wines were more pro-oxidant and exhibited lower hydroxyl radical scavenging and metal chelating abilities than white wines. The effect of in-bottle ageing on antioxidant activity of wines was determined using the ABTS·+ and DPPH· scavenging assays. The TAA and total phenol content of experimental red (Pinotage and Cabernet Sauvignon)and white (Chardonnay and Chenin blanc) cultivar wines, decreased (P < 0.05) during 12 months of storage at 0, 15 and 30 ºC. The TAAABTS of Cabernet Sauvignon and Chardonnay, stored at 30 ºC were lower (P < 0.05) than at 0 ºC. The APABTS and APDPPH of most wines also decreased during storage. The monomeric anthocyanin content of red wines decreased (P < 0.05) rapidly at 15 and 30 ºC. The flavanol content of wines (except Chenin blanc) increased during the first 9 months, decreasing again after 12 months, while minor changes in the flavonol and tartaric acid ester content of both red and white wines were observed. The TAAABTS exhibited a good correlation (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavonol and tartaric acid ester content of red and white wines and flavanol content of white wines. The monomeric anthocyanin content of red wines correlated (r = 0.50, P < 0.001) weakly with TAAABTS. The decrease in the TAAABTS of wines could thus be mainly attributed to a decrease in their total phenol content. / AFRIKAANSE OPSOMMING: Die antioksidant aktiwiteit van fenoliese komponente in wyn is waarskynlik verantwoordelik vir die gesondheidsvoordele daarvan. Die studie het dus gepoog om effek van kultivar en veroudering na bottelering op die antioksidant aktiwiteit van Suid-Afrikaanse wyne te ondersoek. Die antioksidant aktiwiteit van kommersiële Suid-Afrikaanse rooi (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) en wit (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) kultivarwyne is vergelyk deur middel van die 2,2’-azino-di-(3-etielbensotialosien-sulfoon suur)-radikaal katioon (ABTS·+) vernietigingstoets, 2,2-difeniel-1-pikrielhidrasielradikaal (DPPH·) vernietigingstoets en mikrosomale lipiedperoksidasietoets (MLP). Die antioksidant aktiwiteit en die antioksidant kragtigheid (AK) van die rooiwyne was beter as dié van witwyne in al drie antioksidant toetse. Die totale antioksidant aktiwiteit (TAAABTS en TAADPPH) van Ruby Cabernet was die laagste van die rooiwyne, terwyl die AKABTS en AKDPPH van rooiwyn fenoliese fraksies nie van mekaar verskil (P ³ 0.05) het nie. Van die rooiwyne, het Ruby Cabernet en Pinotage die laagste en Merlot die hoogste effektiwiteit in die MLP toets getoon. Die AKMLP van Pinotage se fenoliese fraksies was die laagste van die rooiwyne. Die witwyne, Chardonnay en Chenin blanc, het onderskeidelik die beste en swakste antioksidant aktiwiteit en AK van die witwyne getoon in al drie antioksidant toetse. Askorbiensuur wat in sommige witwyne voorgekom het, het die TAA van hierdie wyne verhoog, maar hul % MLP inhibisie verlaag. Die TAA en % MLP inhibisie het goed gekorreleer (r ³ 0.7, P < 0.001) met die totale fenolinhoud van rooi- en witwyne, asook die flavanolinhoud van rooiwyne en die wynsteensuur-esterinhoud van witwyne. Die % MLP inhibisie het ook goed gekorreleer met die flavanolinhoud van witwyne. Geen korrelasie (P > 0.1) is waargeneem tussen antioksidant aktiwiteit van rooiwyne en hul monomeriese antosianien-inhoud. Rooiwyn was meer pro-oksidatief in die deoksieribose toets as witwyne, maar was die swakste hidroksieradikaalvernietigers en metaalcheleerders.Die effek van veroudering na bottelering op die antioksidant aktiwiteit van wyne soos bepaal met die ABTS·+ en DPPH· vernietigingstoetse, is ondersoek. Die TAA en die totale fenolinhoud van eksperimentele rooi- (Pinotage en Cabernet Sauvignon) en witwyne (Chardonnay en Chenin blanc) het afgeneem (P < 0.05) tydens opberging na bottelering by 0, 15 en 30 ºC oor 12 maande. Opberging by 30 ºC het ‘n groter vermindering (P < 0.05) in die TAAABTS waarde vir Cabernet Sauvignon en Chardonnay veroorsaak as by 0 ºC. Die meeste wyne se APABTS en APDPPH waardes het ook verminder (P < 0.05) na 12 maande. Drastiese vermindering (P < 0.05) in die monomeriese antosianieninhoud van rooiwyne is opgemerk tydens opberging by 15 en 30 ºC. Tydens die eerste 9 maande se opberging het die flavanolinhoud van wyne toegeneem (P < 0.05) en daarna afgeneem (P < 0.05) tot by 12 maande, terwyl flavonol- en wynsteensuuresterinhoud van beide rooi- en witwyne min verandering ondergaan het. Die totale fenolinhoud van rooi- en witwyne, asook die flavonol en wynsteensuur-esterinhoud van rooi-en witwyne en die flavanolinhoud van witwyne, het goed gekorreleer (r ³ 0.7, P < 0.001) met die TAAABTS. In teenstelling met die resultate vir kommersiële kultivarwyne, was die TAAABTS van rooiwyne swak gekorreleer (r = 0.5, P < 0.001) met hul monomeriese antosianieninhoud. Die afname in TAAABTS van wyne tydens veroudering kon dus meestal toegeskryf word aan die afname in hul totale fenolinhoud.

Bibliography: pages 112-130. / The thesis explores the effects on the wine growing district of Stellenbosch of the transformations in the political economy of the Cape Colony in the late nineteeth century. It is the first in depth study of Stellenbosch District and also contributes to other historical analyses concerned with the impact of industrialisation on rural society. Primary sources used include archival records, newspapers and the annual reports of the district branch of the Standard Bank. Labour legislation passed in the aftermath of slavery was most successful in tying labour to the farms when the labour market was confined to the agrarian sector. The mineral and transport revolutions of the late nineteenth century brought about the first major reformulation of social and economic relations in the Western Cape since emancipation. Between cl878 to 1896 wine farmers were hit by the general recession of the 1880s, by the excise tax on brandy, by phylloxera and by periodic labour shortages. Farmers, especially those capitalising their agricultural production, looked to the Zuid Afrikaansche Boere Beskermings Vereeniging and later the amalgamated Afrikaner Bond to press for state aid to wine farmers. In the late nineteenth century farmers finally experienced the implications of the proletarianisation of the rural underclass. Many labourers left to work in the growing urban sector, on the Public Works or in self employment as market gardeners. Farmers in Stellenbosch, like their peers in other societies confronting the implications of industrialisation, regarded labour mobility as illegitimate. They felt threatened by outbreaks of arson and theft, but also by the labourers' new assertiveness. For a time labour relations on the farms took place in a context where labourers had a measure of leverage against the power of the farmer. By 1910 the farmers' world had been righted and this was no longer the case.

Thesis (Ph.D. (Microbiology)) -- University of Limpopo, 2022 / NRF and TIA