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Gross morphology and differentiation of buds of the French hybrid grape variety Seibel 2653Chellappa, Theophilus. January 1957 (has links)
Call number: LD2668 .T4 1957 C46 / Master of Science
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Hardiness studies of some French American hybrid grapesGhosheh, Najati Saleh. January 1956 (has links)
Call number: LD2668 .T4 1956 G46 / Master of Science
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Sun exposure and flavonols in grapesPrice, Steven F. 01 April 1994 (has links)
Graduation date: 1994
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The effect of region, yeast strain and ascorbic acid on the development of a sulphur-like aroma and on Sauvignon blanc wine qualitySwart, Ewarda 12 1900 (has links)
Thesis (MSc Food Sc )--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Highly valued Sauvignon blanc wines, with the distinctive cultivar-typical aromas,
reminiscent of grassy, green pepper or asparagus-like, are produced in some South
African regions. Quite often, however, neutral and sulphur-like, low quality
Sauvignon blanc wines are produced and this phenomenon is of great concern to
wine producers and consumers, and affects our competition on overseas markets,
negatively.
The aim of this study was to investigate the effect of region, ascorbic acid/S02
treatments and yeast strain on Sauvignon blanc wine aroma and quality. Wines were
produced from grapes obtained from the warmer Robertson and the relatively cooler
Stellenbosch regions (1998 season). The juices were treated with different
combinations of ascorbic acid/S02 treatments [commercially available ascorbic
acid/meta preparate, S02 (control), pure ascorbic acid/S02] and Saccharomyces
cerevisiae yeast strains (Vin 13, VL3C, NT 116). The wines were analysed for
esters, higher alcohols, monoterpenes and 2-methoxy-3-isobutylpyrazine (ibMP).
The wines were also sensorially evaluated for wine aroma intensities (fruity/ester,
sulphur-like, grassy/green pepper) and overall quality. Additionally, the synergistic
action of ibMP and the sulphur-containing component, 4-mercapto-4-methylpentan-2-
one (MMP), considered to be the most important impact components of Sauvignon
blanc, was studied. The two components were added, separately and in
combinations at increasing concentrations, to different media. The nuances
perceived, varied from dusty, grassy to green pepper for ibMP and from guava,
sulphur-like to cat urine or "conifer" for MMP.
Significant differences were observed between the wines treated with the different
combinations of ascorbic acid/S02 treatments and fermented with different yeast
strains, irrespective of region. The highest quality, cultivar-typical Sauvignon blanc
wines were produced from the pure ascorbic acid/S02 treatment in combination with
yeast strains Vin 13 and NT 116. This coincided with high ester and low higher
alcohol concentrations, which did not overpower the typical Sauvignon blanc
character. The treatments had, in some cases, a significant effect on monoterpene
levels, but it was concluded that these differences were not big enough to affect wine
quality. Levels of ibMP were too low and could not be reliably measured. Low quality wines, with prominent, undesirable sulphur-like aromas, were produced from
juices, treated with the commercially available ascorbic acid/meta preparate and the
French yeast strain, VL3C.
Techniques, followed to identify the aroma components causing the sulphur-like offflavours,
as MMP or as other sulphur-containing components, were gas
chromatography/mass spectrometry, solid phase microextraction and sniffing.
However, these tests were not successful and studies to identify these off-flavours
should be continued.
It was succeeded in this study to produce Sauvignon blanc wines without the
undesirable, sulphur-like aromas. Although this investigation showed that a newly
developed, commercially available ascorbic acid/meta preparate did not yield any
sulphur-like off-flavours, quite often Sauvignon blanc wines with such off-flavours are
still produced. Further research is needed to clarify this phenomenon. / AFRIKAANSE OPSOMMING: Hoë kwaliteit Sauvignon blanc wyne, met kenmerkende kultivar-tipiese, gras-,
groenrissie- of aspersie-agtige aromas, word in sekere streke van Suid Afrika
geproduseer. Die gereelde produksie van neutrale, en swawelagtige lae kwaliteit
Sauvignon blanc wyne, wek egter nie net groot kommer by wynprodusente en
verbruikers nie, maar het ook 'n negatiewe impak op kompetisie met oorsese markte.
Die doel van hierdie studie was dus om die effek van streek, askorbiensuur/Sóbehandelings
en gisras op Sauvignon blanc wynaroma en kwaliteit vas te stel. Wyne
is berei met druiwe wat verkry is van die warmer Roberston en relatief koeler
Stellenbosch streke (1998 seisoen). Verskillende kombinasies askorbiensuur/So,
behandelings [kommersieel-beskikbare askorbiensuur/meta preparaat, S02
(kontrole), suiwer askorbiensuur/So-l en Saccharomyces cerevisiae gisrasse (Vin
13, VL3C, NT 116) is gebruik tydens die wynbereidingsproses. Spesifieke ester-,
hoër alkohol-, monoterpeen- en 2-metoksi-3-isobutiel metoksipirasienkonsentrasies
(ibMP) is in die wyne bepaal. Die wyne is ook sensories vir wynaroma intensiteite
(vrugtig/ester, swaweiagtig, gras/groenrissie-agtig) en algehele kwaliteit geëvalueer.
Die sinergistiese aksie van ibMP en die swawelbevattende komponent, 4-merkapto-
4-metielpenta-2-oon (MMP), wat beskou word as die belangrikste impakkomponente
in Sauvignon blanc, is addisioneel bestudeer. Hierdie komponente is in toenemende
konsentrasies, individueel en in kombinasies, tot verskillende media gevoeg. Die
nuanses wat waargeneem is, het van stowwerig, gras-, groenrissie-agtig vir ibMP, tot
koejawelagtig, swaweiagtig, katurine, konifeer vir MMP, gevarieer.
Ongeag streke, is betekenisvolle verskille tussen die wyne wat berei is met die
verskillende kombinasies van askorbiensuur/So- behandelings en gisrasse,
waargeneem. Hoër kwaliteit, kultivar-tipiese Sauvignon blanc wyne is berei met
suiwer askorbiensuur/So- in kombinasie met gisras Vin 13 of NT 116. Alhoewel die
hoë ester- en lae hoër alkohol- konsentrasies, hierdie resultate bevestig het, is die
tipiese Sauvignon blanc karakter nie hierdeur oorheers nie. Sommige behandelings
het wel 'n betekenisvolle invloed of monoterpeenkonsentrasies gehad het, maar was
te min om 'n effek op wynkwaliteit uit te oefen nie. Die konsentrasievlakke van ibMP swawelagtige aromas, het egter voorgekom in wyne wat met die kommersieelbeskikbare
askorbiensuur/meta preparaat en die Franse gisras, VL3C, berei is.
Verskeie tegnieke soos gaschromatografie/massa spektrometrie, soliede fase mikroekstraksie
en "sniffing", is gebruik om die komponent, MMP, wat moontlik
verantwoordelik vir hierdie ongewensde swawelagtige wangeure was, te identifiseer.
Die identifikasie hiervan was egter onsuksesvol, en verdere studies is nodig om die
komponent(e) verantwoordelik vir hierdie wangeure, te identifiseer.
Die suksesvolle produksie van Sauvignon blanc, sonder ongewensde swaweiagtig
aromas, was wel moontlik. Alhoewel hierdie studie ook duidelik getoon het dat daar
geen swawelagtige wangeure in die wyne wat met die nuut ontwikkelde,
kommersieel-beskikbare askorbiensuur/meta preparaat berei was, voorgekom het
nie, vind die produksie van Sauvignon blanc wyne met van hierdie wangeure nog
steeds plaas. Verdere navorsing rakende hierdie aspek is nodig.
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The characterisation of selected grapevine cultivars using microsatellitesRoss-Adams, Helen Esther January 2002 (has links)
Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Grapevine supports one of the oldest industries in South Africa today, and is also of
significant international importance. With increasing international trade and the
transport of fruit and other grapevine-derived products between borders, it has
become increasingly important for South African farmers and viticulturalists to ensure
their products conform to strict international market requirements if they are to remain
competitive. Such requirements include the correct and accurate identification of
berries and wines according to cultivar. In light of this, 26 different wine, table grape
and rootstock cultivars, as well as a number of clones from KWV's core germplasm
collection were characterised at 16 microsatellite marker loci. Microsatellite markers
are known for their high level of informativeness, reliability and reproducibility, and
are widely used in the identification and characterisation of plant varieties, population
analyses and forensic applications. Unique allelic profiles were obtained for all but
two plants, which proved to be identical at all loci considered, and thus 'clones'.
These profiles were collated to form a database, containing the DNA fingerprints of
each sample at each locus. The relative levels of informativeness of each marker used
were also determined, and compared with those found in the literature. Six markers
proved to be highly informative, and are promising in the potential application of this
technology to other cultivars. The applicability of microsatellite markers to such
studies is confirmed; this approach could easily be extended to include any number of
cultivars of national and international interest. The results of such an investigation
would have important implications for both the farming and commercial industries
alike. / AFRIKAANSE OPSOMMING: Wingerd ondersteun een van die oudste industriee in Suid-Afrika vandag, en is ook van groat
intemasionale belang. Met die toenemende intemasionale ruilhandel en die vervoer van vrugte
en ander wingerd produkte tussen grense, het dit toenemend belangrik geword vir SuidAfrikaanse
wingerdboere om te. verseker dat hulle produkte voldoen aan die streng vereistes
van die intemasional mark, indien hulle kompeterend wil bly. Hierdie vereistes sluit in die
korrekte en akkurate identifisering van druiwe en wyn volgens kultivar. Met hierdie vereistes
in ag geneem, is 26 verskillende wyn, tafeldruif en wortelstok kultivars, asook 'n aantal klone
van die KWV se kern kiemplasma versameling, gekarakteriseer by 16 mikrosatelliet merker
loki. Mikrosatelliet merkers word gekenmerk deur 'n hoe vlak van informatiwiteit,
betroubaarheid en herhaalbaarheid en word wydverspreid gebruik in die identifisering en
karakterisering van plant varieteite, populasie analises en forensiese toepassings. Unieke
alleliese profiele is vir a1 die plante verkry, behalwe vir twee plante wat identiese resultate by
alle loki opgelewer het en dus as "klone" beskou kan word. Hierdie profiele is bymekaar
gevoeg om 'n databasis te vorm wat die DNA vingerafdrukke van elke monster by elke lokus
bevat. Die relatiewe vlak van informatiwiteit van al die merkers is ook bepaal en vergelyk met
merkers in die literatuur. Ses van die merkers blyk om hoogs informatief te wees en lyk
belowend in die potensiele toepassing van hierdie tegnologie op ander kultivars. Die
toepaslikheid van mikrosatelliet merkers op sulke studies is bevestig; hierdie benadering kan
maklik aangepas word om enige aantal kultivars van nasionale en intemasionale belang in te
sluit. Die resultate van s6 'n ondersoek sal belangrike implikasies inhou vir beide die boerdery
en kommersiele industriee.
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Determinants of producers’ choice of wine grape cultivars in the South African wine industryMusango, Josephine Kaviti 12 1900 (has links)
Thesis (MAgricAdmin (Agricultural Economics))--University of Stellenbosch, 2005. / The wine industry is one of the oldest commercial activities in South Africa. The South African
wine grape industry annually produces more than a million tonnes of grapes, making the country
the ninth largest producer in the world. The total area under wine grape production is divided into
eight regions for administrative purposes. These boundaries are a legacy of the era of controlled
marketing and there is continued meaningfulness of having various classifications such as ‘wine of
origin’ scheme.
The purpose of this study is to identify the factors that determine the producers’ choice of wine
grape cultivars in the wine regions in South Africa. Time series data for the period 1990-2003 were
used to estimate the parameters of linear regression models. Two equations for each wine grape
cultivar in each region were postulated and estimated using Ordinary Least Squares as applied with
Eviews. Further, a stepwise regression as applied in STATISTICA was used to eliminate the
parameters that were not statistically significant at five percent significant level.
In identifying the factors that determine the choice of wine grape cultivars in the regions, the
results showed that each wine grape cultivar in each region has its own factors influencing the
producers’ choice of that specific wine grape cultivar. Same wine grape cultivars in different
regions similarly have its own factors determining the producers’ choice. The implication of this is
that there are differences in terms of the requirements and types of crops and wine grape cultivars
grown in each region. However, the most important result that emerged with regular frequency is
that, the factors determining the producers’ choice of a specific wine grape cultivar for each region
is price of other wine grape cultivars and competitive products in that wine region. The price of
specific wine grape cultivars only had an influence on few wine grape cultivars. The implication is
that the producers in South Africa appears to consider the prices of other wine grape cultivars and
competitive products before making a choice of whether to plant or uproot a specific wine grape
cultivar more than the price of the specific wine grape cultivar. This supports the theory that farm
prices play a key role in allocating resources and in rewarding efficient producers.
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