Orientadores: Helena Teixeira Godoy, Carlos Eugenio Daudt / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-07T11:15:55Z (GMT). No. of bitstreams: 1 Facco_ElizeteMariaPesamosca_D.pdf: 27687746 bytes, checksum: d51d71b95043f23c20948f904cbac415 (MD5) Previous issue date: 2006 / Doutorado / Doutor em Ciência de Alimentos

This diploma thesis has analyzed the effect of organic wine-growing on the wine yeasts population. The wine yeasts were isolated from the Pinot Noir variety. They were identified by the molecular biological method PCR-RFLP. The theoretical research compiles basic information on yeasts, knowledge about the red wine production as well as information on molecular biological methods. The experimental part utilizes the 5,8S-ITS rDNA specific segment for analysis. The segment was amplified using the ITS1 and ITS4 primers and subjected to restriction analysis. The restriction analysis has used these restriction endonucleases - HaeIII, HinfI, Taq?I, AluI and MseI. The BioNumerics software was then used to compare genetic similarity between the isolated yeasts and these were taxonomically classified.

Viniculture and wine-making from a legal viewpoint Abstract This thesis is primarily a theoretical treatise on the legal regulation of viticulture and wine-making in the Czech Republic. It aims to provide an overview of the current legal regulation of the most important institutes of both aforementioned fields, focusing on the Act No. 321/2004 Coll. on viniculture and winemaking, but also other laws and sources of law with regard to EU legislation. Emphasis is placed on the individual aspects of viticultural activity and the subsequent manufacturing of wine products and the conditions for their marketing. This thesis is divided into 8 chapters, including an introduction and a conclusion. The introductory chapters are focused on defining the position of the wine law in the legal system of the Czech Republic and clarifying the relations between the sources of law of viticulture and wine-making in the context of EU legislation. The main body of this thesis is included in chapters No. 3 and No. 4. These chapters are devoted to the current legislation in the field of viticulture and wine-making. The viticultural part of the work is focused mainly on the regulation of vine planting and some aspects which are closely related to viticultural activity, such as phytosanitary care and fertilization. In the wine-making...

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Master of Science

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: South African red wine is often acknowledged world wide as being full bodied and deep in colour. This is often the result of high temperatures that is experienced during the important growth stages of grapes especially post véraison. In the Robertson area in South Africa however, temperatures often exceeds the range for optimal anthocyanin development during these growth stages. The distinction between grapes being technologically ripe and being ripe on a phenolic level is also accepted as an important determining factor for the perfect time to pick grapes. In co-operative wineries such as Robertson Winery (RW) where grapes are delivered from a large area and different producers, it is difficult to individualise grape blocks when it comes to ripeness level in terms of sugar or phenolic ripeness. In most circumstances a generalised set of parameters for deeming grapes ripe or acceptable for delivery is the best substitute. The levels of these parameters are based on research literature that is available for the area as well as data collected through years of maintaining the vineyards of that area. The grape parameters that are currently being used by RW for ripeness and quality are pH, titratable acidity (TA) and sugar level. In recent years RW in conjunction with the Department of Viticulture and Oenology, Stellenbosch University, decided to investigate more parameters to determine the quality of grapes at the time of harvest. Most importantly for the grape growers this quality is connected to a price point and therefore compensation. Two important quality parameters of red wine are the red colour and mouth feel of wine. Anthocyanin and tannins are respectively connected to these two quality attributes and are both widely accepted as quality indicators. Wine with high anthocyanin and tannin content often originates from grapes with a high colour and phenolic profile. The existence of a correlation between grape and wine anthocyanin and tannin content is therefore the basis of attempting to use these parameters in the grape to predict end wine’s colour and phenolic quantity. Determination of anthocyanin and tannin content of grapes has already become part of some private owned wineries’ standard set of determinations. However, sample preparations, extractions and consumables needed are all factors that need to be reduced to make the measurement and therefore the use of these parameters more viable in a co-operative cellar laboratory, where large volumes of grapes are received during harvest. The first objective of this work was to determine the levels of anthocyanin and tannin in red grapes from different vineyard blocks from the producers of RW from three successive vintages. This would give insight as to what can be seen as a low and high anthocyanin and tannin content for grapes received at the cellar. For this purpose, blocks of the most important red wine cultivars for RW was selected and analysed for these compounds. The ranges and average levels of anthocyanin and tannin content were determined using measurement techniques that could be used by any winery. The average mono flavanol and total colour level of the grapes were found to be lower than those often reported in literature, with total grape flavanols being higher. However, a wide range of values for these compounds were found that correlated with those found in other studies. The possible reasons for differences in levels of occurrence of these compounds were discussed and mostly pertain to differences in cultivar, micro climatic and season. The second objective was to determine the correlation between levels of colour and phenolic compounds in grapes and their corresponding wines. Such correlations will form the foundation for the use of phenolic content to predict the colour and phenolic potential of the wine and possibly wine quality as well. When the grape and wine colour and phenolic data were correlated for all seasons and cultivars inclusive it was found that grape and wine colour showed better correlations than for instance total phenols and tannins. This was especially true for total colour pigments in red grapes, measured with HPLC, when correlated with certain spectrophotometric analysis of wine colour. Cultivar and season as well as the synergism between the two were further investigated for its role in affecting correlations. When these relationships were further differentiated by season and by cultivar the resulting correlations varied. This work contributed a great deal of information to support the use of grape colour and phenolic compounds for the prediction of end wine colour and phenolic composition. The third objective was to investigate near infrared spectroscopy (FT-NIR) as a viable option to rapidly measured anthocyanins, tannins and total phenolics in red grapes. If proven successfully, this could be employed by a large cellar such as RW. FT-NIR has been used with success on grape extracts and in this instance the focus was to establish a calibration on the grape homogenate itself. Preliminary results showed that FT-NIR could be applied for the use of determination of anthocyanin and tannin levels in red grapes originating from RW. The prediction of total phenols was not found to be as accurate, but this could also be due to the reference method that was used. This work brought some interesting, practical information not only of importance for RW, but all wineries that are concerned with improving the basis on which grape quality is determined. The use of aerial data mapping for indicating areas regarding important grape colour and phenolic parameters was used in this study and is a very visual way of showing the distribution of certain ripeness parameters over a large area. Correlations between the grape and wines of such a large amount of red grape blocks for a specific area have not also been reported in South Africa before. The use of FT-NIR to determine anthocyanins and tannin concentrations in grape homogenates is also novel for its use in South African wineries. This work may assist grape and wine producers as well as analysts on the phenolic and colour profile of grapes and wines from RW. / AFRIKAANSE OPSOMMING: Suid-Afrikaanse rooiwyn word wêreld-wyd geken aan ‘n dieprooi kleur en vol struktuur. Die grootste rede vir hierdie verskynsel is hoë temperature wat ervaar word tydens rypwording en veral na véraison. In die Robertson wynstreek is temperature egter tydens rypwording dikwels vêr bo dit was as optimaal vir antosianien ontwikkeling beskou word. Die gepaste tyd om druiwe te pluk word nie net gedryf deur die tegnologiese rypheidsvlak nie, maar ook deur fenoliese rypheid. In ‘n koöperatiewe kelder omgewing soos Robertson Wynkelder (RW) word ‘n hoë lading druiwe elke dag ontvant vanaf verskillende produsente oor ‘n breë streek. Dit maak dit moeilik om te bepaal watter druiwe werklik beide tegnologies en fenolies ryp is. Die beste manier om hiervoor te vergoed is om ‘n standaard te stel vir ‘n reeks voorafbepaalde parameters. Die vlakke van die gekose parameters is, word bepaal deur navorsinguitsette sowel as die geskiedkunde data wat ingesamel is vanaf elkeen van die bepaalde blokke. Die parameters wat tans in gebruik is by RW om oesdatum en kwaliteit by inname te bepaal is pH, titreerbare suur (TA) en suiker vlak. Die tekortkoming hier is dat kwaliteit van druiwe beswaarlik met slegs hierdie informasie kan bepaal word, maar dat dit die betaling van die produsent by aflewering wesenlik kan beïnvloed. Dit het RW genoop om in samewerking met die Departement van Wingerd en Wynkunde, Universiteit van Stellenbosch nog parameters te ondersoek wat hierdie rypheid- en kwaliteitsbepaling by inname sou kon versterk. Twee belangrike faktore wat kwaliteit van rooiwyn bepaal is die kleur en struktuur. Antosianiene en tanniene is onderskeidelik verantwoordelik vir hierdie kwaliteits eienskappe van wyn. Wyn wat bestempel word as hoog in kleur en tannien inhoud word dikwels verbind met druiwe wat hoog is in hierdie faktore. Die moontlike korrelasie tussen die antosianien en tannien inhoud van druiwe en die wyn wat daarvan berei word is dus die basis waarop die potensiële toepassing van hierdie parameters berus. Die bepaling van antosianien en tannien vlakke word reeds in sommige laboratoriums gedoen. Die monster voorbereidings tyd, ekstraksies, toerusting en verbruikbare items nodig om hierdie tipe analieses te doen is egter hoog. Die analiese van hierdie komponente is meer lewensvatbaar in groot laboratoriums (soos in ‘n koöperatiewe kelder) waar groter volume druiwe ingeneem word gedurende parstyd. Die eerste doelwit van hierdie studie was om te bepaal teen watter vlakke antosianiene en tanniene in druiwe voorkom, spesifiek van die Robertson area. Die het behels ‘n wye verskeidenheid van blokke, verspreid oor die hele streek wat oor 3 seisoene gemonitor is in terme van veral kleur en tanniene maar ook ander belangrike parameters. Die idee hier is om insig te kry rakende watter vlakke bestempel kan word as laag en hoog in terme van antosianien en tanniene vir die Robertson streek. Daarvoor is slegs die mees aangeplantste rooi kultivars gebruik. Die verspreiding en gemiddelde vlakke waarteen antosianien en tanniene voorkom was bepaal deur gebruik te maak van metodes wat as relatief algemeen in laboratoria gebruik word. Die gemiddelde mono-flavonoïed en totale kleur pigment inhoud van die druiwe was laer as van die vlakke wat in die literatuur beskikbaar is, met totale flavanole wat hoër was. Die wyer verspreiding van die waardes het egter beter gekorreleer met die waardes soos beskryf in die literatuur. Die moontlike redes vir die verskillende vlakke word in die studie bespreek en word waarskynlik bepaal deur verskille in kultivar, mikro-klimaat en seisoen. Die tweede doelwit was om te bepaal of daar ‘n korrelasie te vinde is tussen die kleur en tannien inhoud van die druiwe en ooreenstemmende wyne. Sulke tipe korrelasies sal die basis vorm om antosianien en tannien inhoud van wyn reeds in die druiwe fase te kan voorspel. Nadat die ingesamelde druif en wyn data as ‘n geheel beskou was, was dit sigbaar dat die wynkleur parameters beter korrelasies bied as meeste tannien en totale fenole. Dit was veral waar in die geval van totale kleur pigmente soos gemeet met die HPLC teenoor die wynkleur parameters gemeet met spektrofotometriese metodes. Verdere ondersoeke in terme van die impak wat die kultivar en seisoenale kan hê het tot variërende korrelasies gelei.. Hierdie werk het ‘n groot bydrae gelewer om voorspellings van wyn kleur en fenoliese inhoud reeds met sukses vanaf die druif te bepaal. Derdens het die werk fourier transformasie naby infrarooi skandering (FT-NIR) ondersoek as ‘n lewensvatbare metode vir die bepaling van antosianien, tannien en totale fenoliese inhoud van druiwe en wyn. FT-NIR word reeds oor ‘n wye reeks wyne en druiwe ekstraksiemonsters toegepas en die doelwit hier was om druiwe homogenaat as matriks te kalibreer. Voorlopige resultate het bevind dat antosianien en tannien vlakke in druiwe van RW gemeet kan word met die FT-NIR, maar dat die kalibrasie vir totale fenole nog verbeter kan word. Hierdie werk het ‘n wye reeks interessante en prakties bruikbare informasie na vore gebring wat van onskatbare belang is vir RW en ander kelders wat besorgd is oor die verbetering van algemene druifkwaliteit. Geografiese kaarte wat belangrike druifkleur en fenoliese parameters aandui is in hierdie studie gebruik en wys hoe data visueel voorgestel kan word om die geheelindruk van gekose parameters oor ‘n groot area te vergelyk. Korrelasies tussen druiwe en wyn van so ‘n groot hoeveelheid druiwe blokke is nog nooit voorheen in Suid-Afrika getoon nie. Dieselfde geld vir die gebruik van FT-NIR vir die meet van kleur en fenoliese parameters in druiwe homogenate. Hierdie werk kan druiwe- en wynproduseerders sowel as analiste assisteer in terme van die kleur en fenoliese profiel van druiwe en wyn van RW. / Robertson Winery with Mr Bowen Botha as well as THRIP for funding this project

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The quality of wine is largely dependent on environmental conditions and recent studies have therefore focused on agricultural practices in terms of water, soil and biodiversity conservation. The industry aims to create sustainable practice and to protect the natural resources available. Sources of potential grape contamination include: vehicle pollution, pesticides, bushfires and wood preservatives used for trellising systems. The latter have come to the attention of the South African wine industry (e.g. creosote and Copper Chromium Arsenate (CCA) products) as they may have consequences for the environment and wine quality. Creosote is a known pollutant of soil and ground water and the volatile fraction has been monitored in air. Plants may also accumulate polycyclic aromatic hydrocarbons (PAHs), which constitute up to 85% of the mass of creosote, and of which some have been proven carcinogenic. Because of the health risks associated with it, creosote has therefore been restricted for use in most applications in Europe, and also in the United States, Canada and Australia. This study focussed on the sensorial and chemical analyses of environmental and wine samples taken from the area around the creosote stockyard to determine accumulation of creosote-derived compounds. Environmental samples were collected and analysed at different distances from the affected area, over two vintages. Wines were made from grapes grown in vineyard blocks adjacent to the stockyard, to determine the effect of distance and skin contact during alcoholic fermentation treatments on wine taint. A sensory panel was trained for descriptive analysis to determine the intensity of the taint. Analytical methods were developed for the analysis of volatile organic compounds (VOCs) by gas chromatography mass spectrometry (GC-MS) and polycyclic aromatic hydrocarbons by high performance liquid chromatography with diode array detection (HPLC-DAD). The sensory results obtained showed white and rosé wines were perceived as clean, whilst the red wines were associated with burnt rubber/tar taint. The perceived taint decreased as distance from the stockyard increased. Wines made from the Cabernet Sauvignon blocks adjacent to the stockyard also showed an increase of taint with the increase of skin contact. Chemical data obtained showed that the taint consisted of a complex mixture of compounds, each with its own pattern of retention within the vineyard and wine. Only m-cresol was found above odour threshold, and only in red wines. The synergistic effect of some compounds may lead to an increase in the perceived taint. Berries and leaves had higher concentrations of volatile compounds than wines. Leaf contamination varied and followed the general trend in literature where the plants with high lipid content and exposed leaf area were the most contaminated. There may be other compounds present in creosote emissions, aside from those investigated here, with sensory attributes related to the taint found in wines. These compounds are styrene, indene, benzene, toluene, isoquinoline and quinoline and should be included in further investigations. From the PAH analysis of environmental samples and wines, it is evident that the samples closest to the stockyard were affected the most. The contamination varied with the depth of the soil: some of the heavier compounds were found in the samples taken from the deeper levels, whilst nearly all other target compounds were present in the top layer of soil. The concentrations found in the environmental samples were lower than reported in literature. Wines had few PAHs present, but at much higher concentrations than is allowed by EU legislation. From this study it is evident that the stockyard had negative effects on the surrounding environment in terms of sensory and chemical contamination. Recommendations include area rehabilitation by means of bioremediation to protect resources and ensure sustainable and safe production of crops. Industrial emissions should also be regulated and restricted in agricultural areas. Furthermore the use of creosote should be revised, and prohibited for agricultural use. / AFRIKAANSE OPSOMMING: Die kwaliteit van wyn is grootliks afhanklik van die omgewingstoestande. Daarom fokus verskeie onlangse studies op landbou aktiwiteite en die invloed daarvan op die omgewing in terme van water, grond en biodiversiteit bewaring. The wyn industrie se doelwitte sluit volhoubare praktyke in, wat die natuurlike hulpbronne bewaar en beskerm. Druiwe kan deur middel van die volgende bronne besoedel word: brandstof uitlaatgasse, insekdoders, veldbrande, gifstowwe wat gebruik word vir houtperservering wat dan verder aangewend word vir opleistelsels. Houtperservering (Koper chroom arsenaat (CCA) en kreosoot) het veral in die laaste paar jaar onder aandag gekom in die wynbedryf van Suid-Afrika as gevolg van die invloed daarvan op die omgewing en die uiteindelike wynkwaliteit. Kreosoot is ‘n gekende gifstof wat verantwoordelik is vir grond en grondwater besoedeling en wat gemonitor word in die atmosfeer. Plante akkummuleer ook poli-sikliese aromatiese hidro-koolstowwe (PAHs), wat to 85% uitmaak van die massa van kreosoot. PAHs is karsinogenies en dus is daar baie navorsing op die molekules reeds gedoen. Die gesondheidsrisikos gepaardgaande met kreosoot het gelei tot die streng geregulasies tans ingestel in Europa, die Verenigde State, Kanada en Australië. Hierdie studie het gefokus op die sensoriese en chemiese analises van omgewings- en wyn-monsters geneem van die omliggende area van die kreosoot palewerf om die akkumulasie van kreosoot-afgeleide-verbindings. Omgewingsmonsters was versamel en geanaliseer om verskillende afstande vanaf die bron van besoedeling (palewerf) te ondersoek oor ‘n twee jaar periode. Wyne is gemaak van die druiwe wat afkomstig is van die blok aangeplant langs die palewerf. Die wyne is ondersoek in terme van afstand vanaf die kreosoot bron asook oenologiese invloede, dopkontak gedurende alkoholiese fermentasie, op die kontaminasie beskryf in wyn. Die wyne is ook oor ‘n twee jaar periode voorberei en sluit die 2011 en 2012 seisoen in. ‘n Sensoriese paneel is opgelei om die beskrywende analises op die wyn uit te voer met die doel om die intensiteit van kontaminasie te identifiseer. Analitiese metodes is ook ontwikkel vir die analise van vlugtige organiese verbindings(VOCs) met gas chromatografie-massa spektrometrie (GCMS) en poli-sikliese aromaties hidro-koolstowwe (PAHs) met hoë druk vloeistof chromatografie. Die sensoriese resultate bekom het wit en rosé wyne as skoon laat blyk, terwyl rooi wyne meer geassosieer was met die gebrande rubber/ teer afgeur beskrywing. Die waargeneemde afgeur het afgeneem soos wat die afstand vanaf die palewerf toegeneem het. Wyne gemaak van die Cabernet Sauvignon blokke langsaan die palewerf het ook ‘n toename in die afgeur gehad met ‘n toename in dopkontak. Chemiese data bekom beeld uit dat die afgeur uit ‘n komplekse mengsel van verbindings bestaan, elk met sy eie patroon van verspreiding en verbinding in die wingerd as ook in die wyn. Net m-kresol was gevind bo die reuk drumpel, dit het ook net in rooi wyne voorgekom. Die sinergistiese effek van die verbindings mag egter bydra tot die waargeneemde afgeur. Druiwekorrels en blare het hoër konsentrasies van die vlugtige verbindings gehad as wat gemeet is in die wyne. Blaar kontaminasie het ook baie gewissel en het ooreengestem met die algemene tendens wat in literatuur beskryf is, naamlik dat plante met ‘n hoër lipid inhoud en grootter blaar oppervlak die meeste gekontamineer word. Daar mag egter nog baie ander verbindings bydra tot die waargeneemde afgeur gevind in die wyn. Spesifieke verbindings wat wel ‘n rol kan speel in kontaminasie en wat voorkom in die vlugtige gedeelte van kreosoot is styreen, indeen, benzeen, tolueen, isoquinoleen die vlugtige verbindings van kreosoot. Die verbindings moet ingesluit word vir verdere studies wat gedoen word op die kreosoot geassosieerde afgeur. Die PAHs analise op die omgewingsmonsters en wyne het gelei tot die bevestiging dat die naasliggende omgewing die meeste geaffekteer is. Die kontaminasie wissel in terme van die diepte in die grond wat die gifstowwe voorkom: die swaarder molekulêre verbindings is tot in die dieper vlakke waargeneem terwyl al die gemete verbindings in die boonste lae teenwoordig was. Die vlakke wat waargeneem is in dié studie is egter laer as wat voorheen in literatuur gevind is in ‘n kreosoot geaffekteerde omgewing. Wyn het PAHs teenwoordig gehad, alhoewel slegs twee verbindings gemeet is, het dit in hoër vlakke voorgekom as wat sekere Europese regulasies as toelaatbaar spesifiseer. Vanaf die studie resultate blyk dit, dat die palewerf se negatiewe invloed op die omliggende omgewing beide meetbaar was in sensories en chemiese kontaminasie. Voorstelle sluit onder andere die rehabilitasie van die omliggende omgewing deur middel van bioremediasie in. Om sodoende die natuurlike hulpbronne in die area te bewaar asook om volhoubare en veilige verbouing van gewasse te verseker. Industriële besoedeling en afval moet ook gereguleer word en beperk word in landbou areas. Verder moet die gebruik van kreosoot heroorweeg word en strenger regulasies moet in plek gestel word om aan internastionale standaarde te voldoen. / Financial support from Winetech, Trip and UFS

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The relationships between leaf and fruit represent a fundamental concept in perennial plants. This concept allows to understand and to manage, with regard to farming, the balance of a vine, which is important in terms of fruit quality (i.e. fruit composition), mainly when it comes to producing wines of different categories and styles. The understanding of vine structure, physiology and vine functioning ultimately allows for appropriate recommendations to be given with regard to farming procedures. These include the adaptation of the canopy architecture to achieve a certain yield per vine, the determination of an appropriate fruit microclimate as well as the prediction of harvest dates. One of the central notions of vine balance involves the relationship between the source and the sink organs. The definition of source-sink relationships incorporates several concepts, including the ability of a source tissue to produce carbohydrates through photosynthesis, the transport of these carbohydrates to various plant organs-tissues via appropriate transport channels, and the assimilation and storage of the carbohydrates in the sink organs. In past years, a number of simple ratios have been created to incorporate the relationship between source and sink organs and thereby define vine balance in order to aid in practical management decisions (choice of a training system, irrigation, canopy manipulation etc.). However, vine functioning is very complex and cannot be defined accurately by simple, static ratios. More integrated and dynamic physiological indicators of vine balance and functioning are needed in order to understand the complex communication between organs and ultimately improve on farming practices. In order to achieve this, a better grasp of source-sink relationships, including the signalisation between organs and the functioning of the transport tissues is required. A two year experiment was proposed to study the interaction between source and sink organs using a combination of both primary shoot girdling methods and berry classification according to size. Girdling removes the bark and phloem tissue, thereby interrupting carbon import as well as water flow to the bunch to a certain degree. The aim of the study was to demonstrate the complexity of vine functioning by investigating the dynamics of berry sugar and water accumulation (used as physiological indicators) and the influence thereof on berry fresh mass evolution. Furthermore, the use of berry sugar loading was proposed as an improved physiological indicator of vine balance as it is directly linked to source and sink functioning. Sugar production and the dynamics of berry sugar accumulation rely on photosynthesis which in turn is dependent on stomatal conductance and therefore also incorporates the effects of external abiotic factors (temperature, light and water). It furthermore gives a direct indication of sink functioning as it shows the progressive accumulation of sugar throughout the ripening period and the possible consequences on berry volume evolution. A primary shoot which bore two bunches was used to represent a biological replicate. The lower bunches were girdled above and below in order to completely isolate them from any carbohydrate import. These bunches, along with the upper ungirdled bunches and two control bunches from another shoot were sampled. The berries from these bunches were classified according to diameter, thereby providing the unique opportunity to study berries of the same volume/size. Measurements were done to determine the fresh and dry masses of the sampled berries, as well as to analyse the concomitant sugar concentrations. It was found that girdling clearly had an effect on berry sugar dynamics and the method was improved in the second year of the trial. Girdling in interaction with berry classification according to diameter demonstrated that berries from the same size could have different sugar concentrations. It further showed that, to a certain degree, a relationship exists between the first rapid phase of sugar accumulation and the post véraison increase in berry fresh mass, until the plateau of fruit sugar accumulation, which generally occurs around a sugar concentration of 20 Brix. Additionally, and more importantly, it was found that vine functioning and the balance between the source and the sink organs may be controlled to a certain degree. There is a strong degree of compensation within a vine which results from signalling between and within organs. When taking the results of this study into consideration, it becomes clear that the classical ratios used to quantify the complex relationships between the fruit and the leaves may not be completely adequate to do so. The current way of looking at source-sink relationships and thereby determining whether a vine is balanced or not is over-simplified and there are numerous limitations involved in this approach. The vine is far more complex and various aspects must be taken into consideration before any claims can be made concerning source-sink relationships and consequently leaf to fruit balance. / AFRIKAANSE OPSOMMING: Die verhoudings tussen blaar en vrug verteenwoordig ‘n fundamentele konsep in meerjarige plante. Begrip van hierdie konsep maak dit moontlik om in boerdery die balans van ‘n wingerdstok te verstaan en bestuur. Hierdie wingerdbalans is belangrik in terme van vrugkwaliteit (d.w.s. vrugsamestelling), hoofsaaklik met betrekking tot die produksie van wyne van verskillende kategorieë en style. Begrip van die wingerdstok se struktuur, fisiologie en funksionering maak dit moontlik om gepaste aanbevelings te maak rakende boerdery prosedures. Dit sluit in die aanpassing van die lower argitektuur om ‘n sekere opbrengs per wingerdstok te verkry, die vasstel van ‘n geskikte vrug mikroklimaat asook die voorspelling van oesdatums. Een van die sentrale denkwyses rondom wingerdstok funksionering behels die die bron-vragpunt verhouding. Die definisie van bron-vragpunt verhoudings inkorporeer verskeie konsepte, insluitende die vermoë van ‘n bronweefsel om koolhidrate te produseer deur fotosintese, die vervoer van hierdie koolhidrate na verskeie plantorgaan weefsels via die gepaste vervoerkanale asook die opname en berging van hierdie koolhidrate in die vragpunt organe. In die verlede is ‘n aantal eenvoudige verhoudings geskep om die verband tussen die bron en vragpunt organe te beskryf en sodoende die wingerdstokbalans te definieer met die doel om ondersteuning te bied in praktiese bestuursbesluite (die keuse van opleistelsel, besproeiing, lowermanipulasie, ens.). Wingerdstok funksionering is egter baie kompleks en kan nie akkuraat gedefinieer word deur eenvoudige, statiese verhoudings nie. Meer geïntegreerde en dinamiese fisiologiese aanwysers van wingerdstokbalans en funksionering is nodig om die komplekse kommunikasie tussen organe te verstaan en uiteindelik boerdery praktyke te verbeter. Om dit te bereik is ‘n beter begrip van bron-vragpunt verhoudings asook die seinoordrag tussen organe en die werking van die vervoerweefsels nodig. ‘n Twee jaar lange eksperiment is voorgestel om die interaksie tussen bron- en benuttingsorgane te ondersoek deur gebruik te maak van beide die primêre loot ringelering metode en korrel klassifikasie volgens grootte. Ringelering verwyder die bas en floëem weefsel en onderbreek sodoende koolstof invoer sowel as watertoevoer na die tros tot ‘n sekere mate. Die doel van die studie was om die kompleksiteit van wingerdstok funksionering aan te toon deur die dinamika van suiker en water akkumulasie in die korrel te ondersoek asook die invloed daarvan op korrel vars massa ontwikkeling. Verder is die gebruik van korrel suikerlading voorgestel as ‘n beter fisiologiese aanduiding van wingerdstok funksionering aangesien dit direk geassosieer is met bron-vragpunt funksionering. Suikerproduksie en die dinamika van suiker akkumulasie in die korrel berus op fotosintese wat weer afhanklik is van stomatale geleiding en daarom ook die effek van eksterne abiotiese faktore (temperatuur, lig en water) inkorporeer. Dit gee verder ‘n direkte aanduiding van die funksionering van die vragpunt organe omdat dit die progressiewe akkumulasie van suiker gedurende die rypwordingsperiode aantoon, asook die moontlike gevolge op korrelvolume ontwikkeling. ‘n Primêre loot wat twee trosse dra is gebruik om ‘n biologiese herhaling te verteenwoordig. Die laer trosse is bo en onder geringeleer om hulle heeltemal te isoleer van enige koolhidraat invoer. Hierdie trosse, tesame met boonste ongeringeleerde trosse en twee kontrole trosse vanaf ‘n ander loot is gemonster. Die korrels van hierdie trosse is geklassifiseer volgens hulle deursnee, om sodoende die unieke moontlikheid daar te stel om korrels van dieselfde volume/ grootte te bestudeer. Metings is gedoen om die vars en droë massas van die gemonsterde korrels te bepaal, asook om die gepaardgaande suikerkonsentrasies te analiseer. Daar is gevind dat ringelering duidelik ‘n effek gehad het op korrelsuiker dinamika en die metode is verbeter in die tweede jaar van die proef. Ringelering in wisselwerking met korrel klassifikasie volgens korrel deursnee het aangetoon dat korrels met dieselfde grootte verskillende suikerkonsentrasies kon hê. Dit het verder aangedui dat daar, tot ‘n sekere mate, ‘n verhouding bestaan tussen die vinnige fase van suiker akkumulasie en die na-véraison toename in korrel vars massa, totdat die plato in suiker akkumulasie bereik word, gewoonlik rondom ‘n suikerkonsentrasie van 20 Brix. Daarbenewens, en van groter belang, is gevind dat wingerdstok funksionering en die balans tussen die bron en vragpunt organe onder ‘n mate van beheer is. Daar is ‘n sterk mate van kompensasie binne ‘n wingerdstok wat die gevolg is van seinoordrag tussen en binne organe in die wingerdstok. Wanneer die resultate van hierdie studie in aanmerking geneem word, word dit duidelik dat die klassieke verhoudings, wat gebruik word om wingerdstok funksionering en balans mee te bepaal, moontlik nie beduidend betekenisvol is nie. Die wyse waarop bron-vragpunt verhoudings tans beskou word is, tot ‘n mate, ‘n oorvereenvoudiging en daar is heelwat beperkinge betrokke by hierdie benadering. Die wingerd is baie meer kompleks en verskeie aspekte moet in aanmerking geneem word voordat enige bewering gemaak kan word rakende bron-vragpunt verhoudings. / The University of Stellenbosch and Winetech for financial support

Thesis (DSc)--Stellenbosch University, 1961. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Fermentation of the grape must into wine is one of the most important steps in winemaking. Selected yeast strains of Saccharomyces cerevisiae have been used for many years to ensure complete and even fermentations. The formation of volatile compounds also occurs during fermentation and will influence the sensory perception of the wine. The main objective of the research was to study the sensory and chemical composition of 1992 Oregon Riesling, Chardonnay and Pinot Noir wines fermented with different commercial S.cerevisiae strains. In the first study, Free-Choice Profiling was used to study the sensory profiles of all three varieties after 7 and 20 months of aging. This method was used in order to utilize a panel of expert winemakers for the tastings. The sensory data analyzed through Generalized Procrustes Analysis showed that some strains were similar while others were different in terms of aroma and flavor at 7 months of age. After 20 months of aging, differences and similarities were still present although the sensory profiles were different from the young wines. This last finding showed that differences are still present after a period of aging. In the second study, the chemical composition of all three varieties and the volatile composition of selected wines of Riesling and Chardonnay were studied. In both white varieties, statistical differences in titratable acidity, residual sugar, volatile acidity and malate content resulted from fermentation with different yeast strains. The volatile composition was qualitatively similar, but some quantitative differences, as relative concentration, were found. Whether or not those differences had a sensory impact was not investigated. Results of the present study showed the need for further studies in order to understand the role of yeast in flavor development. Relationships between sensory profiles and volatile composition could help winemakers to understand the influence of a selected strain on a particular variety and to select yeast strains to optimize wine quality. / Graduation date: 1995