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Regional groupings, competitiveness and the potential for clusters in the wine industrySussman, Wayne January 2013 (has links)
Before 1994 the South African wine industry was largely isolated from the global market. Access to markets after 1994 meant that South Africa had to adapt its product quality, style and operating procedures to compete internationally. In recent years, labour unrest and trade regulations have hampered both the reputation and the ability of South African wine producers to penetrate the export market. Using the theoretical framework of cluster theory and generic marketing this inquiry investigates whether regional groupings and clusters could result in the South African wine industry becoming more competitive.
This inquiry examines the role of regional identity, generic marketing, research and development, policy, and leadership in driving competitiveness in the wine industry and whether the potential for clusters exists through wine routes in South Africa. The study employs an exploratory research model which utilised semi structured interviews.
The findings suggest that the research and development component of South Africa’s wine industry lags behind other New World wine producing nations, and that none of the three tiers of government are in the process of creating conditions which would be conducive for the formation of clusters. The results also indicate that wine routes have a positive effect on regional identity, and that generic marketing complements the activities of boutique wine farmers. / Dissertation (MBA)--University of Pretoria, 2013. / lmgibs2014 / Gordon Institute of Business Science (GIBS) / MBA / Unrestricted
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Chemical composition and color attributes of Foch and deChaunac wines at various agesScaman, Christine H. January 1987 (has links)
Phenolic and color parameters of Marechal Foch and deChaunac wines of 1980 through 1983 vintages were analysed to determine variety and aging effects. Centroid Mapping Optimization together with the Simultaneous Factor Shift algorithm were used to determine the HPLC operating conditions which resolved the maximum number of phenolic components of whole red wine. A ternary gradient system using 1 % acetic acid : methanol : acetonitrile was changed from 100:0:0 to 4.8:82.8:12.4 in 130.6 minutes. A flow rate of 1.1 mL/min and a temperature of 32.9 °C were used. The HPLC system was used to separate at least 50 components from each injection of wine and of an ethyl acetate extract of wine. Foch wines were found to have more catechin and epicatechin than deChaunac wines. Peak areas for the ethyl acetate extracts common to all wines, and areas of peaks in the chromatograms of the whole wine, not present in the neutral extract, were used to form a data set for multivariate analyses.
Strong linear correlations were found between tristimulus and spectrophotometry measurements for each wine. The color of Foch wines was more stable and contained more brown and yellow hues than deChaunac wines, as determined by tristimulus measurements.
Total pigment levels of each wine and various fractions of the total, including ionized, un-ionized, polymeric and sulfur dioxide-bound anthocyanins, were determined spectro-photometrically. Total anthocyanin levels (un-ionized and ionized) in deChaunac wines decreased significantly with increasing age but remained constant in Foch wines. Tannin levels as determined by absorbance readings at 280 nm and by the Folin-Coicalteu reagent method were highly correlated. Foch had more flavonoid and less nonflavonoids than deChaunac wines.
The different color parameters, pigment and tannin fractions, as well as titratable acidity, pH and individual organic acids were used as a second data set of analytical parameters for multivariate analyses. A third data set composed of the combination of the analytical data and the HPLC peak areas was also used. Differences between the four vintages of wines, the two varieties, and between old and young wines within varieties were found using stepwise discriminant analysis (SDA). Discrimination of variety differences was more successful (100% correct classification by the jackknife procedure) and required fewer variables than classification by age. Cluster analyses, performed with variables chosen by SDA, gave similar results to the SDA. / Land and Food Systems, Faculty of / Graduate
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The Ohio Wine and Wine Grape IndustriesSiffrit, Susan K. January 1976 (has links)
No description available.
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The colour and phenolic content of Robertson Red grape cultivars : distribution, correlation with wines and analysesVan der Merwe, Hanneli 03 1900 (has links)
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
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Bioprocess monitoring and chemometric modelling of wine fermentationsGarlick, Jessica Louise 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Wine fermentation is a continuously changing biological process whereby the raw product,
grape juice is transformed into a high value product wine. In an ideal situation the fermentation
kinetics of batch fermentations should follow the same trend over time. This however is not the
case in industrial wine fermentations where significant batch-to-batch variation is present. The
time trajectories of fermentation processes are therefore often unpredictable in absolute terms.
The monitoring of substrate (sugar) and product concentrations (ethanol) as well as other
quality parameters during a wine fermentation, is therefore of extreme importance to ensure
effective control and management of wine fermentation processes. Conventional methods for
fermentation monitoring are however costly, time consuming and often unreliable. For these
reasons the modern wine industry requires rapid, reliable, non-destructive monitoring
techniques which would meet the criteria of providing critical real-time process information that
is displayed in easily interpretable graphical format, in order to ensure the highest quality and
continuous consistency throughout all the stages of a process. This research study in particular, addressed the current need for alternative fermentation
monitoring strategies that meet these criteria, by evaluating the potential use of spectroscopy as
an analytical technique for fermentation monitoring. The overall objective of this study was to
use chemometric modelling of information obtained by Fourier transform mid-infrared (FT-MIR)
and near-infrared (FT-NIR) spectroscopy, to quantitatively and qualitatively monitor both
alcoholic (AF) and malolactic fermentation (MLF) processes. Towards this objective 11 batch
fermentations elaborated with Oenococcus oeni and Lactobacillus plantarum strains in
respectively a co-inoculation and sequential inoculation scenario, were sampled and analysed
at regular time intervals with FT-MIR and FT-NIR spectroscopy and enzymatic reference
methods during 2011.
Samples were also analysed by gas chromatography flame ionisation detection (GC-FID)
and mass spectrometry (GC-MS) at two critical stages during fermentation, namely 50%
completion of MLF and 100% completion of MLF, in order to obtain a profile of the evolution of
the aroma compounds associated with each inoculation scenario.
Three clearly defined research objectives were set for this project. The first objective
involved the expansion of the existing quantitative platform for fermentation monitoring.
Towards the outcomes of this objective, partial least squares (PLS) calibration models for
prediction of malic acid and lactic acid in fermenting must and wines elaborated in our study,
were established, based on the MIR and NIR spectra. The models showed excellent predictive
abilities in independent test set validation. This outcome made a significant contribution to our
existing PLS calibration capacity, particularly towards monitoring of MLF. Quantitative data
obtained with the PLS models were also used to graphically project the rate of AF in the different batches, by non-linear fitted regression plots that easily visualised the overall patterns
of sugar and ethanol metabolism in the different fermentations.
The second research objective involved the qualitative monitoring of fermentations. This
approach used FT-MIR and FT-NIR spectra together with chemometrics to identify trends
between the different fermentation treatments. Principal component analysis (PCA) clearly
projected the time trend from the onset of fermentation, through AF and MLF. No unique
bacterial trend was however observed with spectroscopy. These results illustrate the potential
of these techniques to be used for modelling of fermentations in industrial situations, through
providing critical information about the evolution of the process. Furthermore, these techniques
provide tools for identifying problematic and deviating fermentations. A spectral conformity test
based on simple calculations of the standard deviation between the absorbance at each
recorded wavenumber in the spectra, further confirmed identification of the critical fermentation
stages. This technique by-passes the need for spectral interpretation and is a very useful
addition, particularly from the industry perspective, to the portfolio of methods established in this
study.
The third research objective adressed the need to evaluate the possibility to discriminate
between the different process stages and LAB treatments using univariate (ANOVA) and
multivariate chemometric techniques such as PCA, PLS discriminant analysis (PLS-DA) and
Soft Independent Modelling of Class Analogy (SIMCA) for possible future interpretative and
classification purposes. The exploratory tool of PCA was used to investigate the similarities and
differences between the chemical footprints of the different treatments. PCA showed clear
differentiation between the two process stages using chemical quantified data. Differentiation
between the LAB treatments was visible with PCA, showing a more prominent separation at
50% completion of MLF. Furthermore the ability of spectroscopy for potential classification was
shown using PLS-DA and SIMCA. This profiling study can be seen as a preliminary study
setting the ground work for further in-depth research into the profiling of different LAB
treatments and inoculation strategies. / AFRIKAANSE OPSOMMING: Wyngisting is ‘n voortdurend veranderende biologiese proses waarvolgens die rou produk,
druiwesap, in ‘n produk van hoë waarde, naamlik wyn, verander word. Onder ideale
omstandighede sou die gistingskinetika van lotgistings dieselfde tendens oor tyd volg. Dit is
egter nie die geval in industriële wyngistings nie, waar noemenswaardige wisseling van lot tot
lot teenwoordig is. Die tydsbaan van gistingsprosesse is dus in baie gevalle in absolute terme
onvoorspelbaar. Die monitering van substraat- (suiker) en produkkonsentrasies (etanol), sowel
as ander kwaliteitsparameters tydens ‘n wyngisting, is van die uiterste belang om doeltreffende
beheer en bestuur van wyngistingsprosesse te verseker. Konvensionele metodes vir die
monitering van gisting is egter duur, tydrowend en ook soms onbetroubaar. Om hierdie redes
vereis die moderne wynbedryf vinnige, betroubare en nie-destruktiewe moniteringstegnieke wat
aan die kriteria sou voldoen vir die verskaffing van kritiese, intydse prosesinligting wat in ‘n
maklik interpreteerbare grafiese formaat vertoon word om die hoogste kwaliteit en voortdurende
konsekwentheid tydens al die stadia van ‘n proses te verseker. Hierdie navorsingstudie het in besonder die huidige behoefte aan alternatiewe
gistingsmoniteringstrategieë wat aan hierdie kriteria voldoen, aangespreek deur die potensiële
gebruik van spektroskopie as ‘n analitiese tegniek vir die monitering van gisting te evalueer. Die
oorhoofse doelwit van hierdie studie was die chemometriese modellering van inligting wat met
behulp van Fourier transform middel-infrarooi (FT-MIR) en naby-infrarooi (FT-NIR)
spektroskopie verkry is om die prosesse van alkoholiese en appelmelksuurgisting (AMG)
kwantitatief en kwalitatief te monitor. Ten einde hierdie doelwit te bereik, is 11 lotgistings met
Oenococcus oeni en Lactobacillus plantarum rasse uitgevoer in scenario’s van ‘n gesamentlike
inokulasie en opeenvolgende inokulasie onderskeidelik. Monsters van hierdie gistings is met
gereelde tydintervalle in 2011 geneem en analises is met FT-MIR en FT-NIR spektroskopie en
ensiematiese verwysingsmetodes gedoen.
Monsters is ook met gaschromatografiese vlam ionisasie-opsporing (GC-FID) en
massaspektrometrie (GC-MS) op twee kritiese stadia tydens gisting geanaliseer, naamlik toe
AMG 50% en 100% voltooid was, om ‘n profiel te verkry van die evolusie van die
aromaverbindings wat met elke inokulasie-scenario verband hou.
Drie duidelik gedefinieerde navorsingsdoelwitte is vir hierdie studie bepaal. Die eerste
doelwit het die uitbreiding van die bestaande kwantitatiewe platform vir gistingsmonitering
behels. Hiervoor is gedeeltelike kleinstekwadraat [partial least squares (PLS)] kalibrasiemodelle
vir die voorspelling van appelsuur en melksuur in die gistende mos en wyne in ons studie op die
basis van MIR- en NIR-spektra bepaal. Die modelle het in onafhanklike geldigheidsbepaling van
die toetsstel uitstekende voorspellingsvermoëns getoon. Hierdie uitkoms het ‘n
noemenswaardige bydrae gemaak tot ons bestaande PLS kalibrasiekapasiteit, veral om AMG
te monitor. Die kwantitatiewe data wat met die PLS-modelle verkry is, is ook gebruik om die tempo van alkoholiese gisting in die verskillende lotte grafies uit te beeld deur middel van
kromlynige passing van regressiepersele, waarmee dit maklik was om die algehele patrone van
suiker- en etanolmetabolisme in die verskillende gistings te visualiseer.
Die tweede navorsingsdoelwit het die kwalitatiewe monitering van gistings behels. Hierdie
benadering het FT-MIR en FT-NIR spektra tesame met chemometrie gebruik om tendense
tussen die verskillende gistingsbehandelings te identifiseer. Hoofkomponentanalise [principal
component analysis (PCA)] het duidelik die tydtendens vanaf die aanvang van gisting, deur
alkoholiese gisting en AMG, geprojekteer. Geen unieke bakteriese tendens is egter met
spektroskopie waargeneem nie. Hierdie uitslae illustreer die potensiaal van hierdie tegnieke om
vir die modellering van gistings in industriële situasies gebruik te word deur kritiese inligting oor
die evolusie van die proses te verskaf. Verder verskaf hierdie tegnieke gereedskap vir die
identifikasie van problematiese en afwykende gistings. ‘n Spektrale gelykvormigheidstoets
gebaseer op eenvoudige berekeninge van die standaardafwyking tussen die absorbansie by
elke aangetekende golfgetal in die spektra het ook die identifikasie van die kritiese gistingstadia
bevestig. Hierdie tegniek omloop die noodsaak vir spektrale interpretasie en is ‘n baie nuttige
byvoeging tot die portefeulje van metodes wat in hierdie studie bepaal is, veral vanuit ‘n
bedryfsperspektief.
Die derde navorsingsdoelwit het die behoefte aangespreek om tussen die verskillende
prosesstadia en melksuurbakterie-behandelings te onderskei deur gebruik te maak van
eenvariant- (ANOVA) en meervariant- chemometriese tegnieke soos PCA, PLSdiskriminantanalise
en sagte onafhanklike modellering van klasanalogie [soft independent
modelling of class analogy (SIMCA)] vir moontlike toekomstige verklarende en
klassifikasiedoeleindes. Die ondersoekende gereedskap van PCA is gebruik om ooreenkomste
en verskille tussen die chemiese voetspore van die verskillende behandelings te ondersoek.
PCA het duidelike differensiasie tussen die twee prosesstadia getoon op grond van chemies
gekwantifiseerde data. Differensiasie tussen die melksuurbakterie-behandelings was met PCA
sigbaar, met ‘n meer prominente skeiding teen 50% voltooide AMG. Verder is die vermoë van
spektroskopie vir potensiële klassifikasie met PLS-diskriminantanalise en SIMCA getoon. Die
profielsamestelling in hierdie studie kan beskou word as ‘n voorlopige studie vir verdere
diepgaande navorsing oor die profielsamestelling van verskillende melksuurbakteriebehandelings
en inokulasiestrategieë. / The National Research Foundation and Winetech
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The effect of a creosote stockyard on the environment, vines and winesVan Zyl, Annette 03 1900 (has links)
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
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A case study of source-sink relationships using shoot girdling and berry classification (Vitis vinifera L. cv. Cabernet Sauvignon)Joubert, Chandre 03 1900 (has links)
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
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Investigating the impact of sulphur dioxide on Brettanomyces bruxellensis at a molecular and cellular levelDuckitt, Edward 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The yeast Brettanomyces was isolated from beer in 1904 and associated with wine thereafter. A
sporulating form, Dekkera, was discovered later. Brettanomyces bruxellensis produces high
levels of volatile phenol off-flavours in wine. Sulphur dioxide (SO2) is the most widely used
chemical preservative in wine. Yeasts have several mechanisms to cope with the SO2, namely
Ssu1p, a membrane bound SO2 transporter; sulphite reduction, sulphite oxidation and
acetaldehyde production. In unfavourable environmental conditions, certain yeasts can enter a
viable-but-non-culturable (VBNC) state which is characterised by reduced metabolic rate,
inability to reproduce on solid media and a reduction of cell size. VBNC can be triggered by
chemical stress such as high SO2 levels. The objectives of this study were to examine the SO2
tolerance of B. bruxellensis and Saccharomyces cerevisiae, to quantify their rates of SO2
accumulation and efflux, determine the effect of SO2 on their energy metabolism and investigate
if B. bruxellensis possesses an orthologue to S. cerevisiae SSU1.
In this study, the identity of a number of Brettanomyces/Dekkera strains was confirmed using
5.8S rDNA-ITS RFLP analysis and DNA sequencing. Sporulation assays were used to confirm
whether these strains belonged to the Dekkera or Brettanomyces genus. A method to
accurately quantify SO2 in laboratory conditions was optimised. Molecular SO2 tolerance was
tested by spotting fresh yeast cultures on media with SO2 and/or ethanol. Tolerance to SO2
and/or ethanol showed highly strain dependent results with S. cerevisiae showing the highest
tolerance levels while B. bruxellensis tolerated SO2 and ethanol poorly but certain strains grew
well with only SO2. The SO2 accumulation and efflux rates of 3 S. cerevisiae strains and 3 B.
bruxellensis strains were determined. It was shown that the S. cerevisiae strains followed the
same trends as previously found in literature whereas B. bruxellensis strains showed similar
trends but displayed highly variable strain-dependent results. B. bruxellensis CB63 and S. cerevisiae VIN13 were investigated for their response to SO2 in two
different media, TA and SWM, over a 48-hour and 32-day period respectively. Acetic acid,
acetaldehyde, D-glucose, D-fructose (only in SWM) and ethanol (only in TA) were regularly
monitored over the time course of each experiment. SO2 had the greatest impact on
B. bruxellensis with decreased rates of glucose consumption and ethanol production as well as
increased acetic acid. Acetaldehyde peaked shortly after SO2 addition with the subsequent
restarting of sugar consumption for certain samples. This suggests that sufficient acetaldehyde
was produced to bind free SO2 to reduce SO2 stress. Volatile phenols were quantified for day 32
of the SWM experiment. An increase of 4-ethyl guaiacol was correlated to higher molecular SO2
levels. SO2 negatively affected both yeasts energy metabolism, forcing the yeasts metabolism
to adapt to ensure survival.
In general, SO2 was shown to have a negative impact on all aspects of a yeasts growth and
metabolism and that SO2 tolerance is highly strain dependent and a far more complicated
characteristic than currently understood. / AFRIKAANSE OPSOMMING: Die gis Brettanomyces is in 1904 uit bier geïsoleer en daarna met wyn geassosieer. 'n
sporulerende vorm, Dekkera, is later ontdek. Brettanomyces bruxellensis produseer hoë vlakke
van vlugtige fenol afgeure in wyn. Swaweldioksied (SO2) is die mees gebruikte chemiese
preserveermiddel in wyn. Giste het verskeie meganismes om SO2 te hanteer, naamlik Ssu1p, 'n
membraan-gebonde SO2 transporter, sulfietvermindering, sulfiet-oksidasie en
asetaldehiedproduksie. In ongunstige omgewingstoestande kan sekere giste 'n lewensvatbare,
maar nie-kultiveerbare (LMNK)-toestand aanneem wat gekenmerk word deur verlaagde
metaboliese tempo, onvermoë om voort te plant op soliede media en 'n vermindering van die
selgrootte. LMNK kan veroorsaak word deur chemiese stres, soos hoë SO2-vlak. Die doelwitte
van hierdie studie was om die SO2 -bestandheid van B. bruxellensis en Saccharomyces
cerevisiae te ondersoek, hul spoed van SO2 -opneming/akkumulasie en -uitskeiding te
kwantifiseer, die invloed van SO2 op energiemetabolisme te bepaal en te ondersoek of B.
bruxellensis oor ‘n soortgelyke geen as die S. cerevisiae SSU1 beskik.
In hierdie studie is die identiteit van 'n aantal Brettanomyces/Dekkera-stamme bevestig deur
5.8S rDNA-ITS RFLP-analise en DNA-opeenvolging te gebruik. Sporulasietoetse is gebruik om
te bevestig of hierdie stamme aan die genus Dekkera of Brettanomyces behoort. 'n Metode om
SO2 onder laboratoriumtoestande akkuraat te kwantifiseer, is geoptimiseer. Molekulêre SO2-
bestandheid is getoets deur vars giskulture op media met SO2 en/of etanol te groei.
Bestandheid teen SO2 en/of etanol het stam-afhanklike resultate getoon, S. cerevisiae wat die
hoogste toleransievlakke getoon het, terwyl B. bruxellensis SO2 en etanol swak tolereer, maar
sekere stamme het goed gegroei met slegs SO2. Die SO2-akkumulasie en -uitskeidingtempo
van 3 S. cerevisiae-rasse en 3 B. bruxellensis-stamme is bepaal. Daar is gevind dat die S.
cerevisiae-rasse dieselfde tendens soos voorheen in die literatuur beskryf, gevolg het, terwyl B.
bruxellensis-stamme soortgelyke tendense getoon het,maar hoogs veranderlike stamafhanklike
resultate vertoon. B. bruxellensis CB63 en S. cerevisiae VIN13 is ondersoek vir hul reaksie tot SO2 in twee
verskillende media, TA en SWM, oor 'n tydperk van 48-uur en 32-dae onderskeidelik. Asynsuur,
asetaldehied, D-glukose, D-fruktose (slegs in SWM) en etanol (slegs in TA) is gereeld
gemoniteer oor die verloop van elke eksperiment. SO2 het die grootste impak op B. bruxellensis
met ‘n verlaagde tempo van glukoseverbruik en etanolproduksie, sowel as verhoogde asynsuur.
‘n Asetaldehiedhoogtepunt is bereik kort na die SO2-byvoeging met die daaropvolgende
hervatting van suiker wat vir sekere monsters gebruik is. Dit dui daarop dat voldoende
asetaldehied geproduseer is om vry SO2 te bind om SO2-stres te verminder. Vlugtige fenole is
op dag 32 van die SWM-eksperiment gekwantifiseer. 'n Toename van 4-etiel-guajakol korreleer
met hoër molekulêre SO2-vlakke. SO2 het beide giste se energiemetabolisme negatief
beïnvloed, wat die gis dwing om sy metabolisme aan te pas om oorlewing te verseker. Oor die algemeen het SO2 'n negatiewe impak op alle aspekte van giste se groei en
metabolisme, en SO2-bestandheid is hoogs stam–afhanklik. Dit is ook 'n baie meer
ingewikkelde kenmerk as wat tans verstaan word.
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Characterization of Chenin Blanc wines produced by natural fermentation and skin contact : focus on application of rapid sensory profiling methodsWeightman, Jayne 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Producers of South African (SA) dry and semi-dry Chenin blanc table wines are currently
experimenting with winemaking techniques to modulate the flavours of the predominantly fruity
styles of this genre. An important stage during wine style development is sensory profiling
paired with consumer acceptance testing, before wine is produced on industrial scale. With
those aforementioned goals in mind, this study was conducted in partnership with two
commercial SA wine cellars.
The main focus of the study was an investigation into the treatment effects of two winemaking
techniques, respectively grape skin contact and natural fermentation, on the sensory profiles of
experimentally produced Chenin blanc wines. Results obtained with descriptive sensory
analysis (DA) of the wines were compared to those obtained by two rapid sensory profiling
methods, namely projective mapping (PM) and frequency of attribute citation (FC). A consumer
preference study was also done on the wines. In order to understand the treatment effects
better, the dominant non-Saccharomyces yeasts that were present during the natural
fermentations were identified using polymerase chain reaction (PCR), while the major volatile
chemical compounds were identified with chromatography and mass spectrometry.
The sensory and chemical profiles of the naturally fermented wines were significantly different
from those of the inoculated wines. PCR analysis identified some of the yeasts present during
alcoholic fermentation. In comparison to the inoculated fermented wines, the naturally
fermented wines were generally perceived to have more intense and riper tropical fruity aromas,
with enhanced sweetness and reduced intensities of sourness, bitterness and astringency.
The wines fermented on the skins (FoS) had lower ester and volatile thiol concentrations than
the control wines (with no skin contact) and limited skin contact wines. Sensory attributes linked
to the FoS wines included aromas of dried fruit, dried grass and a vegetative character, with an
increased sour and bitter taste and astringent mouthfeel. In contrast, the wines that were
produced with limited skin contact (12 hours) retained their tropical fruity aromas better than the
FoS wines. Limited skin contact seemed to have had a less harsh effect on the taste and
mouthfeel than the FoS wines. A consumer study was done to establish a Generation Y
consumer group’s (18-35 years) preference for the different treated wines. Overall, the naturally
fermented wines, which were described as having a strong tropical fruit character, were
preferred. The FoS wines were generally disliked by the consumers. Results obtained from the three sensory analysis methods, respectively DA, PM and FC, were
similar, thereby confirming the suitability of the rapid methods PM and FC, to extract qualitative
information from the sensory profiling of white wine.
The results of this study made a significant contribution towards validation of rapid sensory
methods for wine evaluation, which are particularly valuable in the context of sustainability and
technology transfer to research and industry alike. The knowledge gained on the chemical
profiles of SA Chenin blanc is novel and this is one of the first reports on the volatile thiol
content of SA Chenin blanc wine. / AFRIKAANSE OPSOMMING: Produsente van Suid-Afrikaanse (SA) droë en semi-droë Chenin blanc tafelwyne
eksperimenteer tans met wynmaaktegnieke om die oorwegend vrugtige style van hierdie genre
te varieer. ‘n Belangrike fase van wynstylontwikkeling is sensoriese profilering van die produkte
met gepaardgaande verbruikersaanvaardingstoetse, voordat die wyne op industriële skaal
geproduseer word. Met dié bogenoemde doelwitte in gedagte, was hierdie studie in
vennootskap met twee kommersiële SA wynkelders gedoen.
Die hooffokus van die studie was om die invloed van twee wynmaaktegnieke, onderskeidelik
druifdopkontak en natuurlike fermentasie, op die sensoriese profiele van eksperimenteel
geproduseerde Chenin blanc wyne te ondersoek. Resultate wat met beskrywende sensoriese
analise (DA) van die wyne verkry is, is vergelyk met dié wat deur twee vinniger sensoriese
profileringsmetodes metodes, naamlik projektiewe kartering (PM) en frekwensie van
kenmerkaanhaling (FC) verkry is. 'n Verbruikervoorkeurstudie is ook op die wyne gedoen. Ten
einde die behandelingseffekte beter te verstaan, is die dominante nie-Saccharomyces giste wat
teenwoordig was tydens die natuurlike fermentasie geïdentifiseer met behulp van die
polimerasekettingreaksie (PCR), terwyl die vernaamste vlugtige chemiese verbindings
geïdentifiseer is met chromatografie en massaspektrometrie.
Die sensoriese en chemiese profiele van die natuurlike gefermenteerde wyne was beduidend
anders as dié van die geiinokuleerde wyne. PCR analise het sommige giste wat teenwoordig
was tydens alkoholies fermentasie geïdentifiseer. In vergelyking met die geiinokuleerde wyne,
het die natuurlik gefermenteerde wyne intenser en ryper tropiese vrugtige aromas getoon, met
‘n verhoogde perspesie van soetheid en laer intensiteite van suurheid, bitterheid en vrankheid. Die wyne wat berei is deur fermentasie op die druifdoppe (FoS) het laer konsentrasies van
esters en vlugtige swawelverbinding gehad, as die kontrole wyne (geen dopkontak) en beperkte
dopkontak wyne. Sensoriese eienskappe gekoppel aan die FoS wyne was geasssosieer met
gedroogde vrugte, gedroogde gras en 'n vegetatiewe aroma, met gepaardgaande verhoogde
suur en bitter smaakpersepsies en ‘n frank mondgevoel. In teenstelling, het die wyne wat
geproduseer is met 'n beperkte dopkontak (12 uur) hul tropiese vrugtige aroma beter behou as
die FoS wyne. Beperkte dopkontak het ook ‘n minder negatiewe uitwerking op die
smaakpersepies van bitterheid en vrankheid gehad. ‘n Verbruikerstudie is gedoen om 'n groep
jong Generasie Y verbruikers (18-35 jaar) se voorkeure vir die verskillende behandelings te
bepaal. Oor die algemeen is die natuurlike gefermenteerde wyne, wat beskryf is met 'n sterk
tropiese vrugtekarakter verkies, terwyl die groep nie van die FoS wyne gehou het nie. Resultate wat verkry is met drie sensoriese analise metodes, onderskeidelik DA, PM en FC,
was soortgelyk en die geskiktheid van die vinniger metodes, PM en FC, om kwalitatiewe
inligting van witwyn se sensoriese eienskappe te verkry, is bevestig.
Die resultate verkry met hierdie studie maak ‘n beduidende bydrae tot die validering van
vinniger sensoriese metodes vir wynevaluering, wat veral waardevol is in die konteks van
volhoubaarheid en tegnologieoordrag na navorsing en die industrie.
Die nuwe kennis wat in hierdie studie gegenereer is met die chemiese profilering van SA
Chenin blanc wyn is baie waardevol en hierdie is een van die eerste narvorsingsprojekte oor die
inhoud van vlugtige swawelverbings in SA Chenin blanc wyn.
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The non-sweet wine trade of England during the fourteenth and fifteenth centuriesJames, Margery Kirkbride January 1952 (has links)
No description available.
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