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Regional Wine Reputation: How It Influences Trade and Consumer Purchasing BehaviorOstrander, Joseph Bernard 01 December 2015 (has links) (PDF)
ABSTRACT
Regional Wine Reputation: How It Influences Trade
and Consumer Purchasing Behavior
Joseph Bernard Ostrander
What are wine trade buyers and wine consumers willing to pay for a bottle of wine based on the reputation of the grape growing region apart from existing corporate branding reputation, variety popularity, or accolades from industry periodicals and celebrity wine critics? Results from a previous study discovered how attitudes about place-of-origin influenced consumer perceptions regarding the quality associated with the wines from that region. Related research also looked at how wine prices depended on the quality associated with a wine region’s reputation when linked to older, and better known wine regions from different countries. The purpose of this research was to examine the attitudes of wine trade buyers and wine consumers to determine how much of an influence American Viticulture Areas (AVAs) have on their purchasing decisions.
A trade survey was conducted during November and December 2014 and sent via email to 1,778 wine trade contacts that were provided by a well-known winery in San Luis Obispo County. Final responses numbered 152 (8.5%) from trade businesses located in the U.S. The majority of participants were from Florida (24%) and California (22%), with 71% being on-premise sales channels while 29% were retail off-premise outlets.
Respondents to the trade survey were asked to rank eight different desirability factors about the wines they selected for resale. The two most desirable features indicated were: 1) Quality product; and 2) Reputation of wine region. However, the choice of wine From a well-known AVA, was only a somewhat to very desirable trait. This could suggest that the wine trade is either unaware or unsure of what an AVA is. Of the 152 wine trade respondents that were asked how often they make a decision to purchase one wine versus another based on where it was produced, 43% indicated they always, or very often do so. Moreover, 81% of the trade respondents indicated that a wine’s place-of-origin did influence their purchasing decision at least somewhat often.
A related survey involving 302 wine consumers was conducted in San Luis Obispo County during October 2014 and February 2015. Responses were collected outside selected grocery stores using the personal interview method. The survey demographics of those consumers that participated in the study were similar to the MRI+ statistics of domestic wine consumers, although there was a higher proportion of younger respondents in the current sample.
Wine consumers were also asked to rate six different features by desirability when making a decision to purchase wine. The two most desirable features indicated by respondents were: 1) Good value for quality; and 2) Varietal. However, wine selected From a respected region, was considered only a somewhat desirable trait. These findings were not surprising since 16% of the total consumers also indicated they did not know the place-of-origin of the wines they purchased. Likewise, 60% of consumers always, or very often Read the label to learn where the wine was produced, while only 38% indicated they always, or very often Make a decision to purchase one wine versus another based on where the wine was produced.
Results suggest that for the typical wine consumer the grape growing region is not an important factor when making a purchasing decision. Conversely, wine trade decision makers do consider a wine’s place-of-origin an important factor when they select wines for their restaurants, wine bar menus, and outlet shelves. Consequently, wine regions should prioritize efforts toward educating the wine trade by highlighting the quality of their area’s winegrowing practices.
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Characterization and evaluation of glucose oxidase activity in recombinant Saccharomyces cerevisiae strainsMalherbe, Daniel Francois 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2010. / ENGLISH ABSTRACT: Popular wine styles prepared from fully-ripened, more mature grapes are characterized
by intense fruitiness and varietal flavors. However, lengthy maturation of
grapes in the vineyard does not only translate into higher flavor intensity but also
into higher sugar levels, which, in turn, leads to wines with higher concentrations of
alcohol. Excessive alcohol levels can compromise wine flavor and render wine unbalanced.
This, along with health issues and anti-social behavior linked to high-risk
alcohol consumption patterns, stricter legislation and increased tax rates associated
with high-alcohol wines, have increased demand for wines with reduced alcohol
concentrations, without loss of the intense fruity aromas. Although low-alcohol
wines can be made using physical post-fermentation processes, such approaches are
often expensive and can impact adversely on wine flavor. As an alternative strategy,
yeast strains are being developed by several research groups to convert some of the
grape sugars into metabolites other than ethanol.
Based on promising results from previous preliminary work, this study focused
on the development of an industrial Saccharomyces cerevisiae wine strain producing
glucose oxidase (GOX; b-D-glucose:oxygen oxidoreductase, EC 1.1.3.4).
GOX oxidizes b-D-glucose to D-glucono-d-lactone and gluconic acid (GA) extracellularly,
thus preventing its entry into glycolysis, thereby diverting a portion of the sugar carbon away from ethanol. The GOX-encoding gene from the foodgrade
fungus, Aspergillus niger was used to construct three cassettes (GOX1, GOX2
and GOX2LOX). In these gene cassettes, the A. niger GOX gene was placed under
the regulation of the S. cerevisiae phosphoglycerate-kinase-1 gene promoter
(PGK1P) and terminator (PGK1T ). To facilitate secretion, in GOX1 the yeast mating
pheromone-factor a secretion signal (MFa1S) was fused to the GOX gene, and
in GOX2 the native A. niger secretion signal of GOX was used. These gene cassettes
were each integrated into the genome of two laboratory yeast strains (BY4742 and
S1278b) and one industrial wine yeast strain (VIN13). An additional integration
cassette, designated GOX2LOX, was constructed to knock out the IME1 gene in S.
cerevisiae. In GOX2LOX, GOX2 was fused to a loxP cassette. VIN13-D1 was obtained
by integrating a single copy of GOX2LOX into the IME1 locus. To generate
an asporogenic, GOX-producing wine yeast, VIN13-D2 was created by sporulation,
micromanipulation and re-diploidisation of VIN13-D1. Comparative analysis indicated
that (i) GOX2 resulted in higher levels of extracellular glucose oxidase activity
than GOX1; and that (ii) the levels of secreted glucose oxidase activity in the wine
yeast transformants were sufficiently high to conduct follow-up small-scale wine
fermentation trials.
The wine yeast transformant, VIN13-D1 was evaluated under red and white experimental
winemaking conditions. Results from this work indicated that glucose
oxidase was produced and secreted by VIN13-D1 that dominated the fermentation
to the end, but also that the enzyme was not highly active under the evaluated winemaking
conditions. Consequently, no significant decrease in ethanol concentrations
was observed in the wine made from VIN13-D1 when compared to that from
VIN13. Wine samples were analyzed by Fourier transform-middle infrared spectrometry
(FT-MIR) to determine the chemical composition and Gas chromatography
with a flame ionization detector (GC-FID) to evaluate the concentrations of
aroma compounds. The levels of gluconic acid were determined by enzymatic assays.
Multivariate data analysis (PCA and PLS1-discrim) was applied to highlight
significant differences between the wines made by VIN13 (wild-type) and VIN13-
D1. Chemometric projections of the score plots for all results allowed insight into
all significant variation up to three principal components (PCA) or PLS components,
which showed very clearly that GA is a key factor in evaluating the effect of
GOX in VIN13-D1 fermentation with regard to VIN13 fermentations. The VIN13-
D1 effect manifestations were best shown on PLS1-discrim score plots that revealed that, of the restricted variable subsets the FT-MIR-compounds and GC-compounds
yielded better results, with the GC-compounds displaying greater discriminability
between cultivars and VIN13 / VIN13-D1. It can be concluded from these results
that the greatest influence of VIN13-D1 produced wines could be observed in the
aroma components, but, because there were also discriminability effects discernable
in the FT-MIR-compounds, thus the flavor components were also affected.
The activity of GOX in grape juice was further investigated in controlled small
scale fermentations performed in a bio-reactor. It was confirmed that GOX is active
under aerobic conditions, inactive under anaerobic conditions, and can be activated
instantly when an anaerobic culture is switched to aerobic conditions (simulated
micro-oxygenation). These fermentations showed that glucose oxidase is active in
grape juice, and that oxygen play a key-role in the enzyme’s activation. Finally, it
was shown with the help of a simplified model, that under ideal conditions, GOX
secreted from VIN13-D1, can be employed to reduce the ethanol by a predefined
concentration for the production of low alcohol wines.
This work gives more insight into how to employ a GOX-producing wine yeast
during winemaking and strongly suggests the use of micro-oxygenation to activate
the enzyme in order to reduce available glucose, thereby diverting a portion of the
sugar carbon away from ethanol production. / AFRIKAANSE OPSOMMING: Gewilde wynstyle word dikwels gemaak van volryp, goed ontwikkelde druiwe,
gekarakteriseer deur intense aromas en smaakkomponente wat direk met spesifike
kultivars geassosieer word. ’n Nadelige gevolg om druiwe te lank aan die wingerdstok
te laat bly hang sodat meer intense geurkomponente kan ontwikkel, is die
toename in suikerinhoud. Hierdie addisionele suiker lei tot wyne met hoër alkoholvlakke.
Te hoë alkoholvlakke kan wyn ongebalanseerd laat voorkom en die
smaak nadelig beïnvloed. Dit, tesame met gesondheidsredes en anti-sosiale gedrag
wat gekoppel kan word aan die inname van te veel alkohol, strenger wetgewing
aangaande dronkbestuur en die toename in belasting op wyne met ’n hoër alkoholinhoud,
het aanleiding gegee tot ’n aanvraag vir wyn met ’n verlaagte alkoholinhoud,
sonder dat aroma- en geurkomponente ingeboet word. Alhoewel daar sekere
fisiese/gemeganiseerde prosesse beskikbaar is om die alkohol in wyn te verwyder of
te verminder, is ’n nadeel dat hierdie prosesse baie duur en arbeidsintensief is, en dat
dit deur sommige wynpuriste as te ingrypend in die ‘natuurlike’ proses van wynmaak
beskou word. Sommige van hierdie alkoholverwyderingsprosesse kan ook die wyn se geur- en aromakomponente nadelig beïnvloed. As alternatief tot hierdie
fisies-chemiese prosesse word wyngiste reg oor die wêreld deur verskillende
navorsingsgroepe ontwikkel sodat van die druifsuikers nie na alkohol omgeskakel
word nie, maar eerder ander metaboliete.
Belowende navorsingsresultate in ’n voorafgaande studie het aanleiding gegee
tot hierdie navorsingsprojek. In hierdie studie word daar klem gelê op die ontwikkeling,
deur middel van genetiese manipulering, van ’n industriële wynras van
Saccharomyces cerevisiae sodat dit in staat sal wees om glukose-oksidase (GOX;
b-D-glukose:suurstof oksidoreduktase, EC 1.1.3.4) te produseer. GOX kan reeds
b-D-glukose in die medium oksideer na glukoonsuur (GA), wat sodoende verhoed
dat dit verder gemetaboliseer word via glukolise, en dit het tot gevolg dat
’n gedeelte van die beskikbare suiker nie omgeskakel word na alkohol nie. Die
strukturele glukose-oksidase-geen (GOX) van die voedsel-gegradiëerde fungus, Aspergillus
niger is gebruik tydens die konstruksie van drie kassette (GOX1, GOX2 en
GOX2LOX). Binne hiedie geenkassette is A. niger se GOX-geen se transkripsieinisiëring
en -terminering onafhanklik deur die fosfogliseraat-kinase-1-promotor
(PGK1P) en termineerder (PGK1T ) bewerkstellig. Om uitskeiding van GOX uit die
gis te bewerkstellig, is daar van die a-spesifieke gisferomoon-a-faktor (MFa1S)
in GOX1 gebruik gemaak, en in GOX2, van A. niger se eie natuurlike sekresiesein.
Hierdie geenkassette is binne-in die genoom van twee labaratoriumgisrasse
van S. cerevisiae (BY4742 en S1278b) asook een industriële wyngisras (VIN13)
geintegreer. ’n Addisionele integreringskasset (die sogenaamde GOX2LOX-kasset)
is gemaak om die IME1-geen van S. cerevisiae te elimineer. Binne die GOX2LOXkasset
is GOX2 aan ’n loxP-kasset gekoppel. Die nuwe wyngis VIN13-D1 is verkry
deur ’n genomiese integrasie van GOX2LOX binne-in die IME1-lokus. Om die niesporulerende
GOX-produserende wyngis VIN13-D2 te verkry, is VIN13-D1 gesporuleer,
onderwerp aan mikromanipulasie en toegelaat om te herdiploidiseer. Ontledings
het aangedui dat (i) GOX2 aanleiding gegee het tot hoër vlakke van ekstrasellulêre
glukose-oksidase aktiwiteit in vergelyking met GOX1; en (ii) dat die
vlakke van uitgeskeide biologies-aktiewe glukose-oksidase vir die wyngisrasse aansienlik
hoër was. Dit het verdere kleinskaalse wynfermentasies geregverdig.
Die getransformeerde wyngis VIN13-D1 is op eksperimentele skaal in die maak
van rooi- en witwyn geëvalueer. Ontledings van hierdie eksperimentele wyne het
daarop gedui dat glukose-oksidase deur die VIN13-D1-gisselle geproduseer en suksesvol
uitgeskei tydens die wynmaakproses is, en dat VIN13-D1 die fermentasie gedomineer het en die alkoholiese gisting voltooi het. Resultate het egter ook aangedui
dat die geproduseerde glukose-oksidase nie baie aktief was onder die wynmaaktoestande
wat in hierdie eksperimentele wynmaakproses gegeld het nie, en gevolglik
was daar nie ’n drastiese verlaging in die alkoholvlakke sigbaar toe VIN13-D1
se wyne met VIN13 se wyne vergelyk is nie. Wynmonsters is deur middel van
Fourier-transformasie-mid-infrarooispektroskopie (FT-MIR) ontleed ten einde die
chemiese samestelling te bepaal, en gaschromatografie-massaspektrometrie (GCMS)
is aangewend om die wynaromakomponente te bepaal. Die vlakke van glukoonsuur
is deur middel van ensiematiese reaksies bepaal. Multiveranderlike data-analise
[hoofkomponentanalise (PCA) en parsiële kleinte kwadrate (PLS1) diskriminantanalise]
is op die data van die verskeie analitiese tegnieke toegepas om onderliggende
veskille tussen die wyne van VIN13 (wilde-tipe) en VIN13-D1 uit te wys. Chemometriese
projeksies het aangetoon dat daar wel beduidende variasies sigbaar was tot en
met drie hoofkomponente en/of PLS-komponente wat duidelik aandui dat glukoonsuur
’n sleutelfaktor was ten opsigte van die uitwerking wat GOX op VIN13-D1-
fermentasies in vergelyking met VIN13-fermentasies. VIN13-D1 effek manifestasies
is die beste waargeneem op grafieke wat PLS1-diskriminantanalise-data bevat.
Verder het PLS1-diskriminantanalise ook aangetoon dat van die ‘groepe’ wat
gebruik was tydens die analise, die FT-MIR-komponente en die GC-komponente
beter resultate gelewer het. Die GC-komponente het hulle verder daartoe geleen
om tussen die verskillende kultivars en VIN13/VIN13-D1-fermentasies te diskrimineer.
Daar kan dus met sekerheid gesê word dat die grootste invloed in VIN13-D1
wyne sigbaar is in die aromakomponent, maar omdat daar wel ook variasies sigbaar
was in die MIR-komponente, dat die smaakkomponente ook beïnvloed was.
Die aktiwiteit van GOX in druiwesap is verder ondersoek deur gebruik te maak
van kleinskaalse fermentasies in bioreaktors. Daar is bevestig dat die VIN13-D1-
geproduseerde GOX biologies-aktief was tydens aerobiese kondisies, onaktief was
tydens anaerobiese kondisies, en onmiddelik geaktiveer kon word wanneer ’n anaerobiese
fermentasie aerobies gemaak word (gesimuleerde mikro-oksigenasie). Hierdie
verskillende fermentasies dui daarop dat glukose-oksidase inderdaat aktief is in
druiwesap, en dat suurstof ’n sleutelfaktor is tydens die aktivering van die ensiem.
Met behulp van ’n vereenvoudigde model kon aangetoon word dat tydens ideale
toestande dit wel moontlik is om die alkoholvlakke te verlaag na ’n voorafbepaalde
konsentrasie vir die bereiding van lae-alkohol wyne.
Hierdie studie verskaf verdere insig hoe om ’n GOX-produserende wyngis gedurende die wynmaakproses vir die verlaging van die alkoholvlakke te benut. Verder
is dit duidelik dat suurstof van kardinale belang is vir die aktivering van die glukoseoksidase-
ensiem en dat ’n tegniek soos mikro-oksigenasie ’n belangrike rol in hierdie
verband tydens die wynmaakproses sou kon speel.
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Analysis of endo-polygalacturonase activity in a recombinant yeast containing a reconstituted PGU1 geneVan Wyk, Herine 03 1900 (has links)
Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2009. / The PGU1 gene encodes an endo-polygalacturonase, an enzyme that degrades pectin. Although the presence and function of this gene is well characterized in Saccharomyces cerevisiae, its regulation is very complex and not yet fully understood. Yeast producing a highly active polygalacturonase (PG) during alcoholic fermentation could potentially improve filtration and turbidity and also enhance extraction of certain aroma compounds. This could replace the addition of expensive commercial enzyme preparations that often contain unwanted enzymes.
The first objective of this study was to evaluate PGU1 expression in recombinant strains of S. cerevisiae that originally lacked the PGU1 gene. A functional PGU1 gene and its promoter were successfully re-introduced into their native position in the genomes of five wine strains. Three of these strains recovered PG activity while two did not transcribe the gene and subsequently lacked activity. The three strains that recovered activity were used in microvinification experiments to determine the effect of PG-producing yeast on the aroma profile of the wine. No significant differences were observed in the volatile compounds production between the recombinants and their respective wild types, but some tendencies arose, especially for the monoterpene geraniol.
The second objective of this study was to analyze the PGU1 gene and promoter from Saccharomyces paradoxus RO88 (a strain that exhibits high PG activity) and to compare it to those of S. cerevisiae S288C in order to identify differences that could potentially be responsible for the difference in their PG activities. Comparison of the gene sequences revealed several amino acid differences, one of which was in the peptide secretion signal. Analyses of the promoters also indicated some potentially important differences. Furthermore, S. cerevisiae strain VIN13, RO88 as well as two interspecies hybrids (all displaying varying PG activities) were compared under winemaking conditions. Clear differences were observed for the production of certain compounds. RO88 and the hybrids produced higher concentrations of certain volatile compounds, although they were not strong fermenters. Two recombinants, each containing a PGU1-overexpressing plasmid (one with the PGU1 gene from S. paradoxus and the other from S. cerevisiae), were also used in vinification to determine the effects of the different PGU1 gene on the aroma profile of the wine. Unfortunately, the plasmids were unstable and lost during the fermentation. Nevertheless, some tendencies were observed that indicated possible higher production of certain compounds by the recombinants compared to their wild types.
This study identified that regulation of the PGU1 gene differs between strains with different genetic backgrounds. Certain differences were observed in the PGU1 gene and promoter
sequences between S. cerevisiae and S. paradoxus that could potentially be the reason for the difference in their PG activities. From an oenological point of view, the presence of PGU1 in the genome of a fermenting strain tends to increase the aromatic potential of wine. These results provide a good platform for further studies on the PGU1 gene.
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Co-expression of aroma liberating enzymes in a wine yeast strainDe Klerk, Daniel 03 1900 (has links)
Thesis (Msc (Viticulture and Oenology. Institute for Wine Biotechnology))--University of Stellenbosch, 2009. / Monoterpenes are important aroma compounds in certain grape varieties such as Muscat, Gewürztraminer and Riesling and are present as either odourless, glycosidically bound complexes or as free aromatic monoterpenes. These complexes occur as monoglucosides or, when present as diglycosides, most commonly as 6-O-α-L-arabinofuranosyl-β-D-glucopyranosides of mainly linalool, geraniol, nerol and citronellol.
The release of monoterpenes from non-volatile glycosidically bound precursors occurs either by acid hydrolysis or enzymatic hydrolysis. High temperature acid hydrolysis causes a rearrangement of the monoterpene aglycones and a decrease in the aroma and changes in the aromatic characteristics of monoterpenes and is therefore not suitable. Enzymatic hydrolysis does not modify the monoterpene aglycones and can be an efficent method to release potentially volatile monoterpenes.
α-L-arabinofuranosidase and β-glucosidase are important enzymes responsible for the liberation of monoterpene alcohols from their glycosides. Glycosidases from Vitis vinifera and Saccharomyces cerevisiae are severely inhibited by winemaking conditions and this leads to unutilized aroma potential, while commercial preparations of aroma liberating enzymes are crude extracts that often have unwanted and unpredictable side effects. It is therefore of interest to investigate alternative measures to release glycosidically bound monoterpenes to increase the floral aroma of wine without side activities that impact negatively on wine.
Heterologous α-L-arabinofuranosidases and β-glucosidases have previously been expressed in S. cerevisiae and these studies have evaluated and found increased glycosidic activities against both natural and synthetic substrates.
In this study, we expressed the Aspergillus awamori α-L-arabinofuranosidase (AwAbfB) in combination with either the β-glucosidases Bgl2 from Saccharomycopsis fibuligera or the BglA from Aspergillus kawachii in the industrial yeast strain S. cerevisiae VIN13 to facilitate the sequential enzymatic hydrolysis of monoterpene diglycosides. Enzyme assays and GC-FID (Gas Chromatography with a Flame Ionization Detector) results show a significant increase in the amount of free monoterpene concentrations under winemaking conditions in the strain co-expressing the AwAbfB and the Bgl2. The increases in free monoterpene levels obtained were similar to those obtained with a commercial enzyme preparation, LAFAZYM AROM. Sensorial evaluation confirmed the improvement in the wine aroma profile, particularly the floral character. This yeast strain permits a single culture fermentation which improves the sensorial quality and complexity of wine. Further investigations on the factors influencing the stability and reactivity of monoterpenes during alcoholic fermentation are needed.
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Screening and characterisation of wine related enzymes produced by wine associated lactic acid bacteriaMtshali, Phillip Senzo 03 1900 (has links)
Thesis (Msc (Viticulture and Oenology))--University of Stellenbosch, 2007. / Among the factors contributing to wine complexity and quality, wine aroma is one of the
most important factors. Wine aroma is the outcome of interaction among different
compounds produced from the grapes, during fermentation as well as during the ageing
process. Apart from its origin from grapes, fungi and yeasts, wine aroma can also be
derived from the metabolic activity of wine lactic acid bacteria (LAB). These
microorganisms are usually associated with malolactic fermentation (MLF) which normally
occurs after alcoholic fermentation. MLF is beneficial to wine due to its contribution to
deacidification, microbiological stabilisation and wine aroma formation, with the latter being
the most important area of interest in our study. The production of volatile aromatic
components in wine can, in part, be achieved through the hydrolytic action of enzymes
produced by LAB associated with wine. These enzymes include β-glucosidase, protease,
esterase, lipase and glucanase. Most of the work done on bacterial enzymes has been on
LAB from food sources other than wine, in which these enzymes contribute to the flavour
development of some cheeses, yoghurt and other fermented foods. The activity of these
enzymes during wine fermentation has mostly been concerned with β-glucosidase from
Oenococcus oeni. Only in recent years has there been a renewed interest in evaluating
the activity of β-glucosidase in other genera of wine LAB.
The overriding goal of this study was to screen and characterise wine-related enzymes
produced by LAB associated with wine. All the LAB isolates tested in this study were
obtained from IWBT culture collection and were previously isolated from five different
wineries situated in the Western Cape region, South Africa. We first screened isolates
using classical methods. The isolates were grown on agar medium supplemented with
appropriate substrate analogues in order to evaluate the activity of enzymes (i.e. β-
glucosidase, glucanase, lipase and esterase). The colonies exhibiting enzymatic activity ...
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Authentication of Sauvignon blanc wine in terms of added flavouringsTreurnicht, Jeanne 03 1900 (has links)
Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: The varietal character of Sauvignon blanc wine is mostly defined by the balance between
tropical and green vegetative flavour nuances. Grape derived methoxypyrazines are the main
aroma contributors towards green vegetative flavours. Methoxypyrazines are heat and light
sensitive. Due to warm climatic conditions in South Africa, methoxypyrazine levels decrease
during grape ripening.
The addition of food flavourings to Sauvignon blanc wine, a practice known as spiking, has
occurred in the past to improve the green character of the wines. Adding flavourings to wine and
selling the wine as natural certified wine is illegal in South Africa. Currently, adulterated
Sauvignon blanc wines are identified using gas chromatography–mass spectrometry (GC-MS)
and liquid chromatography–mass spectrometry (LC-MS) methods to quantify methoxypyrazines
and compare levels to an established database. Although of high sensitivity, GC-MS and LCMS methods are costly and time consuming, therefore not optimal for routine screening of
wines. Hence the need for the development of a fast and cost effective method for routine
screening of large amounts of wines to identify adulteration.
Small scale vinification practices were used to prepare experimental Sauvignon blanc wine.
Flavourings were added to Sauvignon blanc grape juice before fermentation, during the
preparation of experimental spiked wines. Control wines, containing no flavouring, were also
prepared. Commercial wines were spiked after fermentation and bottling. Each wine was only
spiked with a single flavouring. The flavourings added were the juice of homogenised fresh
green peppers and commercially available flavourings for wine. The following commercial
flavourings were used: green pepper, asparagus, grassy and tropical.
The above mentioned wines were analyzed using Fourier transform infrared (FT-IR)
spectroscopy, GC-MS, LC-MS and descriptive sensory analysis. The FT-IR techniques used
were Fourier transform mid infrared (FT-MIR) transmission, FT-MIR attenuated reflection and
Fourier transform near infrared (FT-NIR) reflection spectroscopy. The data was interpreted
using the following multivariate statistical techniques: principal component analysis (PCA),
partial least squares discrimination (PLS-D) and conformity testing.
Multivariate models constructed from FT-MIR and FT-NIR data were able to discriminate
between spiked and control wines. Sensory analysis results clearly showed differences between
non-spiked wines and spiked wines with 3-isobutyl-2-methoxypyrazine concentrations 10 times
higher than naturally occurring in wine. Differences between control and spiked wines with
concentrations of 3-isobutyl-2-methoxypyrazine similar to concentrations naturally occurring in
wines could not be detected to prove adulteration conducting sensory analysis. However,
differences between control and spiked wines with levels of 3-isobutyl-2-methoxypyrazine
similar to levels naturally occurring in wines could be detected using FT-IR data in conjunction
with multivariate statistics.
This study showed that, FT-IR spectroscopy in conjunction with multivariate statistical methods
can be a possibility for the screening and identification of wines suspected of adulteration in
terms of added flavourings. Descriptive sensory analysis also proved to be a potentially useful
tool. However screening and training of potential panel members are time consuming. / AFRIKAANSE OPSOMMING: Die variëteitskarakter van Sauvignon blanc wyn word grotendeels gedefinieer deur die balans
tussen tropiese en groen vegetatiewe aromas. Metoksipirasiene is die hoof aroma verbindings
wat verantwoordelik is vir groen vegetatiewe aromas. Metoksipirasien is hitte- en ligsensitief.
Warm klimaatsomstandighede in Suid-Afrika het tot gevolg dat metoksipirasien konsentrasies
daal tydens druif rypwording.
Sauvignon blanc wyne is in die verlede vervals deur middel van die byvoeging van vars groen
soetrissies om die groen vegetatiewe karaktereienskappe van die wyne te bevorder. Die
byvoeging van geurmiddels of plantekstrakte by wyn en verkoop van daardie wyn as
gesertifiseerde natuurlike wyn is onwettig in Suid-Afrika. Tans word vervalsde wyne met behulp
van gaschromatografie-massaspektrometrie (GC-MS) en vloeistofchromatografie-massaspektrometrie (LC-MS) opgespoor. Kwantifisering van metoksiepirasien konsentrasies in wyne
en druiwesappe word vergelyk met konsentrasies in ‘n bestaande databasis. Alhoewel GC-MS
en LC-MS hoë sensitiwiteitsmetodes is, is dit duur en tydrowende metodes, dus nie optimaal vir
roetine sifting nie. Dus word ‘n koste- en tydseffektiewe roetine metode benodig om vervalsing
van wyne op te spoor.
Eksperimentele wyne is op klein skaal berei. Geurmiddels is voor fermentasie by die druiwesap
gevoeg. Kontrole wyne waarby geen geurmiddels gevoeg is nie, is ook berei. Kommersiële
wyne is gegeur na fermentasie en bottelering. Elke wyn is met ‘n enkele geurmiddel gegeur.
Gehomogeniseerde vars groen soetrissie asook kommersieel beskikbare geursels vir wyn is
gebruik. Die volgende kommersiële geursels is gebruik: groen soetrissie, aspersie, gras en
tropiese geursel.
Die volgende analitiese tegnieke is gebruik vir analisering van bogenoemde wyne: Fourier
transformasie infrarooi (FT-IR) spektroskopie, GC-MS, LC-MS en beskrywende sensoriese
analise. Die spesifieke FT-IR tegnieke wat gebruik is, is: Fourier transformasie mid-infrarooi
(FT-MIR) transmissie, FT-MIR verswakte weerskaatsing en Fourier transformasie naby-infrarooi
(FT-NIR) reflektansie. Die volgende multiveranderlike statistiese tegnieke is gebruik ter
interpretasie van data: hoof komponent analise (PCA), parsiële kleinste kwadraat diskriminant
analise (PLS-D) en gelykvormigheidstoetsing.
Multiveranderlike modelle, bereken met behulp van FT-MIR en FT-NIR data, kon diskrimineer
tussen gegeurde en kontrole wyne. Resultate wat verkry is tydens sensoriese analises het
duidelike verskille uitgewys tussen gegeurde en kontrole wyne met betrekking tot 3-isobutiel-2-
metoksipirasien konsetrasies waar 3-isobutiel-2-metoksipirasien konsentrasies 10 keer hoër
was as wat natuurlik voorkom in wyn. Geen beduidende verskille kon waargeneem word in
gevalle waar wyne vervals is met laer konsentrasies van geurmiddels deur sensoriese data te
ontleed nie. Nietemin, statisitiese verskille tussen kontrole en vervalsde wyne kon waargeneem
word vir lae-konsentrasie-geurmiddel vervalsde wyne deur FT-IR data met behulp van
multiveranderlike statisitiese metodes te ontleed.
Hierdie studie het gewys dat FT-IR in kombinasie met multiveranderlike statistiese tegnieke
spesifiek hoof komponent analise (PCA) en parsiële kleinste kwadraat diskriminant analise
(PLS-D) asook gelykvormigheidstoetsing bruikbare tegnieke is om te onderskei tussen kontrole
(egte natuurlike) en vervalsde wyne ten opsigte van die byvoeging van geurmiddels.
Beskrywende sensoriese analise kan ook nuttig gebruik word, alhoewel keuring en opleiding
van paneellede tydrowend is.
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Optimization and evaluation of heterologous lysozyme production in saccharomyces cerevisiaeWilcox, Dale Adrian 03 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Hen egg white lysozyme (HEWL; muramidase; EC 3:2:1:17) is an enzyme
present in high concentrations in chicken (Gallus gallus) egg whites. It hydrolyses
the link between N-acetylmuramic acid and N-acetylglucosamine in Gram positive
bacterial cell walls, resulting in cell death. It is thus active against lactic acid
bacteria (LAB), which may be present in grape juices and musts. These bacteria
are responsible for malolactic fermentation of wines although many species, particularly
of the genera Lactobacillus and Pediococcus, are considered spoilage organisms.
The growth of LAB is therefore closely monitored and controlled during
winemaking. The most common means of control is growth inhibition by chemical
treatment (usually with SO2). Lysozyme is a commonly used wine processing aid,
complementing the antimicrobial activity of SO2 . It allows for lower doses of SO2
to be used, thus improving the wholesomeness of wine. The OIV (Organisation
Internationale de la Vigne et du Vin) approved its use in quantities up to 500 mg per
liter of wine in 1997.
This study evaluated the effect of different secretion signals on the secretion of
lysozyme by the haploid auxotroph Saccharomyces cerevisiae strain FY23. Secretion
by an industrial strain (VIN13) transformed with a single copy of the HEWL gene with the MF-a secretion signal under the control of the PGK1 (phosphoglycerate
kinase 1) prompter and terminator was also evaluated. In the case of FY23 four
secretion signals were used, namely the native lysozyme signal and the S. cerevisiae
mating factor-a signal as well as mutants of these signals. These mutants incorporated
two additional arginines at the N-terminus of the signals immediately downstream
of the terminal methionine. The effect of these mutations was to increase the
positive charge of the secretion signal N-terminals. The secretion signal-lysozyme
fusions were placed under the regulation of the S. cerevisae PGK1 gene’s promoter
and terminator. The resulting expression cassettes were cloned into integrating vectors
YIpLac211 and pDMPOF1b and episomal vector pHVX2. These were used to
transform FY23 and VIN13.
FY23 as well as VIN13 transformants were evaluated in an artificial medium
designed to reflect the nutrient content of grape juice, with particular attention being
paid to assiminable nitrogen. Three hexose concentrations were tested in order to
determine the effect thereof on lysozyme secretion titer.
Lysozyme secreted under all tested growth conditions was found to be too low
for detection by either enzymatic assay or HPLC-FLD. For this reason secreted
lysozyme was isolated and concentrated 10x by means of cation-exchange. Subsequently,
lysozyme concentrations in the concentrates was determined by means of
the aforementioned techniques. SDS-PAGE analysis of lysozyme concentrates was
also performed.
No significant differences were found between native or MF-a secretion signals
and their mutated counterparts in terms of secretion titer or proteolytic maturation.
Lysozyme secreted with the MF-a signal was found to be misprocessed in all cases,
with both an authentically processed and a larger form, in which the secretion signal
was not completely removed, being present. Lysozyme secreted with the native
signal appeared to be correctly processed in all cases. Secretion titer from high
copy number episomal FY23 tranformants was similar to that of integrants containing
a single copy of the gene. Sugar concentration affected lysozyme production,
with higher quantities of the enzyme being secreted when higher initial sugar concentrations
were used. Lysozyme titers were extremely low (< 0:25 mg/L) with
all expression cassettes under all the tested conditions with both FY23 and VIN13.
In the case of the VIN13’s a lower final biomass was found for the secretor strain
tested in comparrison to the VIN13 wild-type. / AFRIKAANSE OPSOMMING: Hoendereierwitlisosiem (HEWL; muramidase, EG 3:2:1:17) is ´n ensiem teenwoordig
in hoë konsentrasies in hoender (Gallus gallus) eierwitte. Dit hidroliseer
die binding tussen N-asetielmuramiensuur en N-asetielglukosamien in Gram positiewe
bakteriese selwande, wat tot seldood lei. Dit is dus aktief teen melksuurbakterieë
(MSB), wat in druiwesap en mos teenwoordig kan wees. Hierdie bakterieë
is verantwoordelik vir appelmelksuurgisting van wyne, hoewel baie spesies, veral
van die genera Lactobacillus en Pediococcus, ook as bederforganismes beskou
word. Die groei van MSB word dus noukeurig tydens wynbereiding gemoniteer en
beheer. Die algemeenste wyse van beheer is groei-inhibisie deur chemiese behandeling
(gewoonlik SO2). Lisosiem is ´n algemeen gebruikte wyntoevoegingsmiddel
en vul die antimikrobiese aktiwiteit van SO2 aan. Met lisosiem kan ´n laer dosis
van SO2 gebruik word, wat lei tot ´n verbetering van die heilsaamheid van die wyn.
Die OIV (Organisasie Internationale de la Vigne et du Vin) het die gebruik daarvan
goedgekeur tot en met 500 mg per liter wyn vanaf 1997. Hierdie studie het
die effek van verskillende sekresieseine op die uitskeiding van lisosiem deur die haploïede ouksotrofe Saccharomyces cerevisiae stam, FY23, geëvalueer. Uitskeiding
deur ´n industriële stam (VIN13), wat getransformeer is met ´n enkelkopie van die
HEWL-gene met die MF-a sekresiesein onder die beheer van die PGK1 (Fosfogliseraat
kinase 1) promotor en termineerder, is ook geëvalueer. In die geval van FY23
is vier sekresieseine gebruik, naamlik die inheemse lisosiemsein, S. cerevisiae MF-
a sein, asook mutante van hierdie seine. Hierdie mutante het twee bykomende
arginienresidu’s by die N-terminus van die seine direk stroom-af van die terminale
metionien. Die effek van hierdie mutasies was om die positiewe lading van die
uitskeidingsein N-terminale te verhoog. Die gevolglike uitdrukkingskassette is in
die integrasievektor YIpLac211 en pDMPOF1b, en die episomale vektor pHVX2,
gekloneer. Dit is gebruik om VIN13 en FY23 te transformeer. FY23, sowel as
VIN13-transformante, is geëvalueer in ´n kunsmatige medium wat ontwerp is om
die voedingsinhoud van druiwesap te weerspieël, met besondere aandag aan assimileerbare
stikstof. Drie heksose konsentrasies is getoets om te bepaal wat die
uitwerking daarvan op die lisosiemsekresietiter is. Onder alle groeitoestande was
die isosiem wat uitgeskei is, te laag om deur ensimatiese toetse of HPLC-FLD
bepaal te word. Om hierdie rede is uitgeskeide lisosiem geïsoleer en 10x gekonsentreer
deur middel van katioon-uitruiling. Daarna is lisosiemkonsentrasies bepaal
deur middel van bogenoemde tegnieke. SDS-PAGE-ontleding van lisosiemkonsentraat
is ook uitgevoer. In terme van sekresietiter of proteolitiese maturasie, is geen
beduidende verskille gevind tussen inheemse of MF-a sekresieseine en hul gemuteerde
eweknieë nie. Lisosiem wat deur die MF-a sein uitgeskei is, is in alle gevalle
foutief geprosesseer, met ´n teenwoordigheid van beide die regte produk en ´n groter
produk, waarin die uitskeidingsein nie heeltemal verwyder word nie. Lisosiem wat
met die inheemse sein uitgeskei is, blyk in alle gevalle korrek verwerk te wees.
Sekresietiter van ´n aantal hoë-kopie episomale FY23-transformante was soortgelyk
aan dié van integrante met ´n enkelkopie van die geen. Suikerkonsentrasie beïnvloed
lisosiemproduksie, met ´n hoër hoeveelheid van die ensiem wat uitgeskei word wanneer
die aanvanklike suiker in hoër konsentrasies gebruik is. Lisosiemtiters was
baie laag (< 0:25 mg/L), met al die kassette onder al die getoetste toestande vir
beide FY23 en VIN13. In die geval van die VIN13’s, is ´n laer finale biomassa vir
die uitskeidingstam in vergelyking met die VIN13 wilde-tipe gevind.
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Screening, identification and characterisation of bacteriocins produced by the wine isolated LABNdlovu, Joseph Buyani 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Lactic acid bacteria (LAB) play a vital role in reducing wine acidity and also contributing to its
aroma and flavour. However, they can also be responsible for many wine spoilage problems that
compromise the quality and value of wine. While Oenococcus oeni contributes positive characteristics to
the sensory properties of wine, certain species of the genera, Lactobacillus and Pediococcus can affect the
wholesomeness of wine by producing undesirable compounds, such as biogenic amines and ethyl
carbamate.
Chemical preservatives like sulphur dioxide (SO2) are used to prevent the growth of spoilage
micro-organisms during the winemaking process. SO2 also acts as a reducing agent and maintains the
benefits of antioxidant properties of the polyphenols of wine. However, there is a worldwide demand to
reduce SO2 levels due to the increasing health related risks and other factors.
All these considerations have increased the interest in research to look for new preservation
strategies, and LAB-produced bacteriocins seem to be a potential alternative that has been explored in the
last decade. Various types of bacteriocins have been identified and characterized. However, there are few
reports on bacteriocins produced by LAB of oenological origin or on bacteriocins present in the finished
wine.
The present study screened 155 LAB isolates from the IWBT culture collection for bacteriocin
production. The isolates originated from South African red wines undergoing spontenous malolactic
fermentation (MLF). Eight strains (5%) were identified to be producers, as evidenced by strong inhibition
zones formed against sensitive organisms on agar plates. The producers demonstrated a broad spectrum of
antimicrobial activity by inhibiting Lactobacillus spp., Leuconostoc mesenteroides, Listeria
monocytogenes and Pediococcus pentosaceus strains. Some of these bacterial genera are important in
winemaking since they are potential wine spoilage bacteria. Hence these strains and/or the bacteriocins
they produce could possibly find application in the food fermentation industry. The physiological results, biochemical tests and sugar fermentation profiles all gave the same
results for the seven isolates, which were indicative of enterococci. The identification through 16S rRNA
gene sequencing revealed that the seven tested isolates were all Enterococccus faecium. RAPD-PCR
fingerprinting gave the same profile for the seven strains confirming that they were all identical on
genetic level. Determining the molecular weight using SDS-PAGE showed the peptides to be below
4.6 kDa in size. PCR amplification of the enterocin P gene, sequencing and BLAST search results
confirmed that all eight strains contained the enterocin P gene from Ent. faecium.
The enterocin tested in this study was heat stable at 100°C (30 min), but lost 50% of its activity at
121°C (15 min). Factors such as bacteriocin production and heat resistance are among many that enable
enterococci to be dominant in fermented products such as dairy foods or meat. Therefore, enterococci
producing bacteriocins have potential applications in various foods and fermented products. The pH tests
showed enterocin to be active over a broad pH range (2-10). Enterocin activity over a wide pH range make them potentially more suitable as natural preservatives of foods and fermented products where
products are acidified or pH decreases due to natural LAB present. They also have potential applications
in oenological process where pH levels are as low as 3 and 4.
Proteolytic enzyme treatments with lysozyme, lipase, lyticase and catalase could not inhibit
enterocin activity. This indicated that their antimicrobial activity was independent of lipid or carbohydrate
moieties or hydrogen peroxide. α-Chymotrypsin and proteinase K inactivated enterocin, which indicated
that the compound was proteinaceous in nature.
Bacteriocin production tested in two of the isolates, #16.3 and 128.1, coincided with the
exponential growth phase which occurred after 6 hours of incubation at 30°C, which was an indication of
primary metabolite kinetics. The highest production of 400 AU/ml was observed after eight hours and
was maintained for several hours (46 hours) in the stationery phase. The bactericidal effect of the cell free
supernatants from #16.3 and 128.1 against the sensitive culture of Lactobacillus pentosus DSM 20314
was clearly demonstrated by complete inhibition of growth for most of the experimental period, while the
control increased exponentially throughout the experiment.
In conclusion, this study has confirmed the isolation and identification of Ent. faecium strains
from wine, a genus that is rarely found in the wine environment. Although one can speculate on the origin
of this bacterium in the wine e.g. human handling and contaminated water, these bacterial isolates
produced enterocin P which have antimicrobial action against wine-related LAB genera and therefore
have a potential role in wine spoilage control. / AFRIKAANSE OPSOMMING: Melksuurbakterieë (MSB) speel ‘n belangrike rol in die redusering van die suurgehalte van wyn
en dra ook by tot die aroma en smaak daarvan. Hulle kan egter ook verantwoordelik wees vir vele
wynbederfprobleme wat die gehalte en waarde van wyn negatief beïnvloed. Hoewel Oenococcus oeni
positiewe karaktertrekke aan die sensoriese eienskappe van wyn verleen, kan sekere spesies van die
genus, Lactobacillus en Pediococcus, die heilsaamheid van wyn beïnvloed deur ongewenste verbindings,
soos biogeniese amienes en etielkarbamaat, te produseer.
Chemiese preserveermiddels, soos swaweldioksied (SO₂), word gebruik om die groei van
bederfmikro-organismes tydens die wynbereidingsproses te voorkom. SO₂ fungeer ook as ‘n
reduseermiddel en onderhou die voordele van die antioksidant eienskappe van die poli-fenole van wyn.
Daar is egter ‘n wêreldwye vraag na die redusering van SO₂-vlakke as gevolg van die toename in
gesondheidsverwante risiko’s en ander faktore.
Al hierdie oorwegings het belangstelling in die navorsing van nuwe preserveringstrategieë laat
toeneem en MSB-geproduseerde bakteriosiene lyk na ‘n potensiële alternatief wat in die laaste dekade
ondersoek word. Verskeie tipes bakteriosiene is geïdentifiseer en getipeer. Daar is egter nog weinig
gerapporteer oor bakteriosiene wat deur MSB van wynkundige oorsprong geproduseer is of oor
bakteriosiene wat in afgeronde wyn teenwoordig is.
Die huidige studie het 155 MSB isolate van die Instituut vir Wynbiotegnologie se
kultuurversameling vir bakteriosien-produsering gegradeer. Agt stamme (5%) is as produseerders
geïdentifiseer, soos gestaaf is deur sterk inhibisiesones wat teen sensitiewe organismes op agarplate
gevorm het. Die produseerders het ‘n breë spektrum van antimikrobiese aktiwiteit by inhiberende
Lactobacillus spp., Leuconostoc mesenteroides, Listeria monocytogenes en Pediococcus pentosaceus
stamme gedemonstreer. Sommige van hierdie bakteriese genera is belangrik in wynbereiding, omdat dit
potensiële wynbederfbakterieë is. Hierdie isolate en/of die bakteriosiene wat dit produseer, kan dus moontlik toepassing in die voedselfermentasiebedryf vind.
Die fisiologiese resultate, biochemiese toetse en suikerfermentasieprofiele het almal dieselfde
resultate vir die sewe isolate, wat indikatief van enterococci was, gelewer. Die identifisering deur 16S
rRNA-basispaaropeenvolging het onthul dat die sewe getoetste isolate almal Enterococccus faecium was.
RAPD-PKR-vingerafdrukke het dieselfde profiel vir die sewe rasse gelewer, wat bevestig dat die
rasse almal identies op genetiese vlak was. Deur die molekulêre gewig vas te stel deur middel van SDSPAGE,
het dit getoon dat die peptiede kleiner as 4.6 kDa in grootte is. PKR-amplifikasie van die
enterosien-P geen, die bepaling van basispaaropeenvolging en BLAST-soekresultate het bevestig dat al
agt rasse die enterosien-Pgeen van Ent. faecium bevat.
Die enterosien wat in hierdie studie getoets is, was hitte-stabiel teen 100°C (30 min), maar het
50% van sy aktiwiteit teen 121°C (15 min) verloor. Faktore soos bakteriosienproduksie en
hittebestandheid, is van die vele faktore wat enterococci in staat stel om dominant in gefermenteerde produkte, soos suiwelprodukte of vleis te wees. Enterococci wat bakteriosiene produseer het dus
potensiële toepassings in verskeie kossoorte en gefermenteerde produkte. Die pH-toetse het getoon dat
enterosien-P oor ‘n breë pH spektrum (2-10) aktief was. Enterosienaktiwiteit oor ‘n wye pH spektrum
maak dit potensieel meer geskik as natuurlike preserveermiddels vir kossoorte en gefermenteerde
produkte waar produkte versuur word of die pH afneem as gevolg van natuurlike MSB wat teenwoordig
is. Dit het ook potensiële toepassings in enologiese prosessering waar pH-vlakke so laag as 3 en 4 is.
Proteolitiese ensiembehandelings met lisosiem, lipase, litikase en katalase kon nie
enterosienaktiwiteit inhibeer nie. Daar is getoon dat hul antimikrobiese aktiwiteit onafhanklik was van
lipiede, koolhidraatdele óf waterstofperoksied. α-Chymotripsien en proteïenase-K het enterosien onaktief
gemaak, wat getoon het dat die samestelling proteïenagtig van nature is.
Bakteriosienproduksie wat in twee van die stamme #16.3 en 128.1 getoets is, het ooreengestem
met die eksponensiële groeifase wat na 6 ure van inkubasie teen 30°C plaasgevind het, en wat ‘n
aanduiding is van primêre metabolitiese kinetika. Die hoogste produksie van 400 AU/ml is na agt ure
waargeneem en is vir etlike ure (46 uur) in die stasionêre fase gehandhaaf. Die bakterie-dodende effek
van die selvrye supernatant van #16.3 en 128.1 teenoor die sensitiewe kultuur van Lactobacillus pentosus
DSM 20314 is duidelik gedemonstreer deur totale inhibisie van groei vir die grootste deel van die
eksperimentele periode, terwyl die kontrole eksponensieel deur die hele eksperiment toegeneem het.
Hierdie studie het dus die isolering en identifisering van Ent. faecium-stamme, ‘n genus wat baie
selde gevind word in ‘n wynomgewing, vanuit wyn bevestig. Alhoewel daar gespekuleer kan word oor
die oorsprong van hierdie bakterie in wyn bv. menslike hantering en besmette water, het hierdie rasse wel
enterosien geproduseer en daarom die potensiaal om ‘n rol te speel in beheer teen verskeie bederf-MSB-genera. / TIA, NRF and THRIP
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Mannoprotein production and wine haze reduction by wine yeast strainsNdlovu, Thulile 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Wine protein haze formation is a major challenge for wine makers, and several wine clarifying agents such as bentonite are used in the industry to protect wine from this occurrence. However, clarifying agents may have an undesirable impact on wine quality. Yeast mannoproteins have been shown to possess haze-protective properties, while also positively impacting on the sensorial properties of the product. However, while such mannoproteins are released into the wine during the wine making process, the amounts are low and therefore of limited oenological significance. However, and although commercial wine yeast strains display significant genotypic and phenotypic diversity, no broader assessment of haze protective activity and of mannoproteins release by different wine yeast strains has been undertaken.
In this study, several yeast strains were screened for their impact on wine haze formation in Chardonnay must and in a grape juice model system. The data show that strains of the species Saccharomyces paradoxus possess better haze protective properties than the common Saccharomyces cerevisiae wine yeast strains. Differences in the nature of the proteins released by these two species were investigated, and indicated that several mannoproteins were released at significantly higher levels by S. paradoxus, and that some of these proteins might indeed contribute to the haze-protective activity. A further exploration of yeast cell wall properties indicated that the cell walls of haze-protective S. paradoxus strains contained higher levels of chitin than non-haze protective strains. Grape chitinases are likely to be primarily responsible for wine haze formation, and the data clearly demonstrate that these enzymes are able to bind to the yeast cell walls, and that strains with higher amounts of chitin in the cell wall will bind more chitinases. This finding suggests that the haze-protective nature of the strains is at least in part linked to the chitin levels of the strains.
Furthermore, the impact of some genetic modifications in two wine strains (namely S. cerevisiae VIN13 and S. paradoxus RO88) suggests that several proteins contribute to wine haze protection. However, none of the mannoprotein-encoding flocculation genes, FLO1, FLO5, and FLO11 showed any impact on this property.
Further studies are required to assess the full impact of the S. paradoxus strains on haze protection. In particular, the possible use of such strains as starter cultures or the use of S. paradoxus yeast hulls as clarifying agent needs to be further explored. / AFRIKAANSE OPSOMMING: Wyn proteïen-waas vorming is 'n groot uitdaging vir wynmakers en verskeie wyn verhelderings agente soos bentoniet word in die wynbedryf gebruik om wyn te beskerm teen die vorming van waas. Hierdie verheldering agente het egter 'n ongewenste impak op wynkwaliteit. Gis mannoproteïene is uitgewys as proteïene met moontlike waas-beskermende eienskappe wat ook 'n positiewe uitwerking op die sensoriese eienskappe van die produk het. Al word hierdie mannoproteïene egter vrygestel in die wyn tydens die wynmaak proses, is die hoeveelhede oor die algemeen te laag om van wynkundige belang te wees. Verder, ten spyte van die beduidende genotipiese en fenotipiese diversiteit van kommersiële wyngisrasse is daar nog geen breër assessering van die waas beskermende aktiwiteit van mannoproteïene, vrygestel deur verskillende rasse, tot dusver onderneem nie.
In hierdie studie is verskeie gisrasse gekeur vir hul impak op wyn waas-vorming in Chardonnay mos en ook in 'n model druiwesap. Die data wys dat rasse van die spesie Saccharomyces paradoxus besit beter waas beskermende eienskappe as die algemene Saccharomyces cerevisiae wyngisrasse. Verskille in die aard van die proteïene wat vrygestel is deur hierdie twee spesies is ondersoek, en dit is aangedui aangedui dat verskeie mannoproteins vrygestel aan aansienlik hoër vlakke deur S. Paradoxus. Dit is ook aangedui dat sommige van hierdie proteïene wel bydra tot die waas-beskermende aktiwiteit.
'n Verdere verkenning van gis selwand eienskappe het aangedui dat die selwande van waas-beskermende rasse van S. paradoxus hoër vlakke chitien as nie-waas beskermende stamme bevat. Druiwe chitinases is waarskynlik hoofsaaklik verantwoordelik vir wyn waas vorming, en die data toon duidelik dat hierdie ensieme in staat is om te bind aan die gis selwande, en dat die stamme met hoër vlakke chitien in die selwand meer chitinases sal bind. Hierdie bevinding dui daarop dat die waas-beskermende aard van die stamme ten minste gedeeltelik gekoppel is aan die chitien vlakke van die stamme. Die impak van sekere genetiese modifikasies in twee verskillende gisrasse, naamlik die S. cerevisiae ras VIN13 en die S. paradoxus ras RO88, dui verder daarop dat verskeie proteïene dra by tot die beskerming teen wyn waas. Geeneen van die mannoprotein-koderende flokkulasie gene, FLO1, FLO5 en FLO11 het egter 'n impak op hierdie eienskap nie.
Verdere studies is nodig om die volle impak van die S. paradoxus rasse op waas beskerming te assesseer. In die besonder, die moontlike gebruik van sulke rasse as 'n inkolasie kultuur of die gebruik van S. paradoxus gis doppe as verheldering agent moet verder ondersoek word.
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Modelling structural and policy changes in the world wine market into the 21st centuryBerger, Nicholas. January 2000 (has links) (PDF)
Includes bibliographical references. Addresses the question of what an economic model of the world wine market suggests will happen to wine production, consumption, trade and prices in various regions in the early 21st century. A subsidiary issue is what difference would global or European regional wine liberalisation make to that outlook, according to such a model. Accompanying CD-ROM comprises spreadsheet written by Nick Berger, November 2000, for the Windows and Office97 versions of Excel; a seven region world wine model (WWM7) - base version projecting the world wine market 1996-2005 as a non-linear Armington model. System requirements for accompanying CD-ROM: IBM compatible computer ; Microsoft Excel 97 or later.
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