Thesis (MScAgric) -- Stellenbosch University, 2005. / ENGLISH ABSTRACT: Winemakers or producers are under constant pressure to reduce the
operational costs for the production of wine. The reason for this being
threefold: Firstly, the number of cellars and estates locally, and
internationally, has grown immensely. Thus, the competition on both the
national and international front has put producers under pressure to reduce
their production cost in order to survive the explosion of brand possibilities on
the consumer's horizons. Secondly, the exchange rate has been one of the
most unpredictable variables which highlight the importance of scenario
planning and sufficient financial planning in order to overcome significant
exchange rate fluctuations which may cause financial strain for the business.
Thirdly, the benefits of using expensive oak barrels for the maturation of
premium quality wines are undisputable. These benefits include the
clarification and decarbonation of wines, decrease in the astringency of
tannins ("softening of tannins"), the evolution of colour, providing
complementary oak aromas which increase the complexity and finesse of
these wines and stabilising the colloid structure of the maturing wine. The
greatest disadvantages remain nevertheless that it is a costly and labour
intensive operation. Oak is an essential part of the flavour profile of many
premium quality wines, and there is still a growing market demand for these
wines. The use of oak barrels for the maturation of premium red wines,
incorporates a specific flavour dimension to the wine (and adding value), has
been the traditional way of storing wines. Well known cellars and Estates all
over the world have build remarkable profiles and identities for their brands.
To alter any principles regarding the use of oak will alter the style of the wines
and will beyond any doubt influence their brand image negatively.
Chapter 1 gives an introduction and the main aims of the study. The
phenolic composition of grapes and oak are a complex mixture of different
molecules which are discussed in Chapter 2. These include those responsible
for the colour (anthocyanins), taste (mainly the tannins) and aroma of the
wine. The composition of the oak barrel can be influenced by its origin,
seasoning of the oak, toasting of the staves, age of the barrel etc. These
factors all affect the chemical composition of the oak (lactones, volatile
phenols, carbohydrate volatiles, hydrolysable tannins etc.) and ultimately, the
wine. The chemical reactions taking place in wine during ageing are also
complex, which makes maturation and research of wine in oak a complex
business.
The challenge, thus, developed to sustain the flavour profiles (oak
attributes) and to reduce the operational costs, without influencing the identity
or profile of the brand negatively. The use of oak derived products like chips, dust, blocks, staves, balls and even extracts was proposed, although it is
considered by-products of the cooperage profession. Some of the major
disadvantages of the use of oak derived products still remain the limited
control over the production process. This may lead to inconsistency in the
quality of these products. Nevertheless, the use of oak derived products and
the availability of these products have grown significantly and with it a need
for research on this field.
Chapter 3 address the results obtained from the maturation of Pinotage,
which is uniquely South African, and Shiraz wines, in different oak type barrels
(French vs. American vs. Russian), as well as treatments with various oak
derived products, and the influence of these oak products on the evolution of
colour, phenolic development and quality of the wines during ageing.
The results obtained in this project correlated with findings in the
literature. The colour density, percentage of red pigment colour and S02
resistant pigments increased, especially in the first three to six months during
ageing in barrels as a result of ellagic tannin extraction from the barrels and
polymerisation reactions, but decreased later as maturation progresses as a
result of precipitation. In some cases the use of oak increased the colour
density significantly with almost 40%. The colour density, total red pigment
colour and total phenolic composition decreased during bottle maturation as a
result of polymerisation. No significant colour differences between the barrel
types could, however, be detected. The use of oak derived products showed
the same tendencies for all colour dimensions, although no significant
differences could be detected between the treatments. The most significant
difference was that new oak barrels contributed more to the development of
colour compared to the oak treatments.
The Gelatine index gives an indication of the degree of polymerisation of
tannins; higher values will indicate tannins which are highly reactive and will
cause an astringent mouth feel. The values should decrease as maturation
progresses and tannins polymerise. Little differences between barrel types
(French vs. American vs. Russian) were found in the one Shiraz, but in the
two Pintage wines the index was the lowest in the wines matured in French
oak after 36 months bottle ageing.
Sensorial tests indicated little quality differences after 36 months between
the different oak types The American oak barrels had, in general, a more
"oaky bouquet", even after 36 months in the bottle. Pinotage matured with
different alternative oak products showed that chips added to barrels tended
to give a higher oak aroma, with a lower fruit compared to the other
treatments. The same wine matured in new barrels, as expected, also had a
very high oak aroma compared to the same wine matured in older barrels.
This led to a higher fruit perception in the latter wines.
Lees contact is a practice more commonly used in the production of white
wines, but may be a dangerous practice in the production of red wines.
Chapter 4 reports on the effect of lees contact during ageing of red wine on
the micro flora and colour after 12 month maturation. No significant
differences in microbial analysis were detected during of barrel maturation
between the wines matured in the lees and the filtered wines for acetic acid,
yeast and lactic acid bacteria. The initial pH differences during cold
maceration and fermentation, however, did influence these numbers, with
higher numbers being observed at higher pH values. However, colour
differences could be detected. The concentration of yellow brown pigments
(measured at 420 nm) was lower in the lees matured wines than in the filtered·
wines which underwent malolactic fermentation in the barrel. Other colour
differences that could be detected were higher colour density and total red
pigment colour in wines as a result of longer skin contact (due to slower
alcoholic fermentation rate).
Thus, manipulation of the skins during alcoholic fermentation, the use of
barrels and/or oak derived products in various stages of vinification and
maturation of wines and additional practices as maturation on lees may be
thus be used to set a certain style of wine which meet a specific market
demand, trend or style. Chapter 5 summarises the results obtained and future
research to be done on wood and wine. This study, however, clearly showed
that the origin and oak type does not influence the colour as much as the
aroma and taste of red wine under South African conditions. / AFRIKAANSE OPSOMMING; Wynmakers of produsente word onder gedurige druk geplaas om die
produksiekoste van wyn te verlaag. Die redes hiervoor is drieledig: Eerstens
het die getal kelders en landgoedere op nasionale en internasionale vlak
geweldig toegeneem. Dus, die kompetisie op beide nasionale en
internasionale gebied plaas produsente onder druk om die produksie koste
van die wyn te verminder om sodoende finansieel die ontploffing van nuwe
moontlike wyne op die horison van die verbruiker te oorleef. Tweedens, die
wisselkoers was altyd een van die meer onvoorspelbare veranderlikes wat die
belangrikheid van scenario-beplanning en weldeurdagte finansiele beplanning
beklemtoon om sodoende groat veranderinge in die wisselkoers, wat
moontlike finansiele druk in die besigheid mag veroorsaak, te oorkom.
Derdens, een van die grootste uitgawes in die produksie proses van is die
verouderingskomponent van kwaliteitswyn.
Die voordele van die gebruik van eikehout vate in die verouderingsproses
van rooiwyne is welbekend. Hierdie voordele sluit in die suiwering van die wyn
in terme van soliede partikels , dekarbonisering (C02-ontgasting}, afname in
die vrank smaak ("sagtheid van die tanniene), die ontwikkeling van die kleur
van die wyn, toevoeging van komplementere hout boeketstowwe wat bydrae
tot die kompleksiteit van die wyn, asook die stabilisering van die kollo"idale
struktuur van die wyn.
Die grootste nadeel bly, nieteenstaande, die geweldige koste verbonde
aan vate, asook die hantering en onderhoud daarvan. Eike hout verwante
boeketstowwe is 'n onmisbare komponent van die aroma profiel van baie
kwaliteitswyne. Daar is 'n groeiende mark vir hierdie tipe wyne. Die gebruik
van eikehout vate vir die veroudering van kwaliteitswyne, behalwe die bydrae
van belangrike geurstowwe (een waarde), was nog altyd 'n tradisionele stap in
die proses. Beroemde kelders reg oor die wereld het uitmuntende mark
identiteite vir hulle self geskep, asook 'n "spesifieke identiteit" vir hulle wyn.
Om enige beginsels aangaande die gebruik van eikehout te verander, sal
sander twyfel die wynstyl verander en moontlik 'n negatiewe effek op die
kelder se identiteit he.
Hoofstuk 1 gee 'n inleiding en die hoof doelstellings van die studie. Die
fenoliese samestelling van druiwe en eikehout bestaan uit 'n komplekse
mengsel van verskillende molekules wat in Hoofstuk 2 beskryf word. Hierdie
sluit in daardie verantwoordelik vir die kleur (antosianiene), die smaak
(hoofsaaklik tanniene) en die aroma van die wyn. Die samestelling van die
eikevat kan beinvloed deur die oorsprong, veroudering van die hout,
roostering, ouderdom van die vat ens. Hierdie faktore beinvloed almal die
samestelling van die houtvat (laktone, vlugtige fenole, hidroliseerbare tanniene ens.) en uiteindelik, die wyn. Die chemiese reaksies wat plaasvind
tydens die veroudering van wyn is ook kompleks, wat die veroudering en
navorsing van wyn in vate 'n komplekse proses kan maak. Die uitdaging,
dus, het ontstaan om die organoleptiese profiel van die wyn (eikehout
boeketstowwe) te behou en terselftertyd die produksiekoste van die wyn te
verlaag. Die gebruik van eikehout verwante produkte soos skaafsels,
blokkies, stawe en balke en selfs eikehout ekstrakte is aanbeveel, alhoewel
dit gesien word as afvalprodukte van die kuiperye Een van die grootste
nadele van eikehout alternatiewe produkte is egter die beperkte
kwaliteitskontrole oor die produksieproses. Dit mag lei tot wisselvalligheid in
die kwaliteit van hierdie produkte. Nieteenstaande het die gebruik van eike
houtverwante produkte en die beskikbaarheid van hierdie produkte geweldig
toegeneem en tesame daarmee die behoefte aan navorsing hieroor.
Hoofstuk 3 bespreek resultate van die gebruik van verskillende eikehout
tipe vate (Frans vs Russies vs Amerikaans), asook die gebruik van eikehout
verwante produkte, op die kleur ontwikkeling, fenoliese samestelling en
kwaliteit van Pinotage (eie aan Suid-Afrika) en Shiraz wyne gedurende vat en
bottel veroudering.
Die ontwikkeling van kleur het verskeie unieke dimensies en resultate
wat verkry is in hierdie projek stem ooreen met literatuur. Die kleurdigtheid,
persentasie rooi pigment en 802 weerstandbiedende pigmente het
toegeneem met veroudering in houtvate (veral in die eerste drie tot ses
maande) as gevolg van ellagitanniene wat geekstraeer word en
gepolimerisasie, maar het later gedurende veroudering afgeneem as gevolg
van presipitasie reaksies. In sekere gevalle het die kontak met hout die
kleurdigtheid met tot 40% vermeerder. Die kleurdighteid, totale rooi pigmente
en totale fenole het tydens bottelverouding afgeneem a.g.v. polimerisasie.
Geen merkwaardige verskille kon egter tussen die verskillende vattipes
gevind word nie. Verskille tussen die houtverwante produkte was ook klein en
het diesefde tendense getoon as die vate. Nuwe vate se impak op die
kleurprofiel en ontwikkeling van verouderde rooiwyne was egter meer
beduidenswaardig as die gebruik van gebruikte vate en behandelings met
eikehout verwante produkte.
Die gelatien indeks verwys na die toestand van polimerisasie van
tanniene. Hoer waardes kan verwag word in jong wyne en dui op hoogs
reaktiewe tanniene. Die waarde sal afneem soos tanniene polimere vorm met
veroudering en sal dus 'n veel minder vrank mondgevoel tot gevolg he. Klein
verskille tussen die vat tipes (Frans vs Amerikaans vs Russies) is opgemerk
in die een Shiraz, maar in die twee Pinotage wyne was die indeks die laagste
in die wyne verouder in Franse eikehout na 36 maande se bottelveroudering.
Sensoriese toetse het aangedui dat daar klein verskille gevind is tussen
die verskillende eiketipes. Die wyn verouder in Amerikaanse eik het, in die
algemeen, 'n sterker eikehoutkarakter gehad na 36 maande
bottelveroudering. Wyn verouder met verskillende alternatiewe houtprodukte
het aangetoon dat eikehouskaafels in vate 'n sterker eikehoutkarakter aan die
wyn gegee het met 'n laer vrugtige aroma in vergelyking met die ander
behandelings. Dieselfde wyn verouder in nuwe vate het oak, soos verwag, 'n
sterk hout boeket gehad in vergelyking met die verouder in ouer vate. Dit het
dan oak gelei dat laasgenoemde wyne 'n sterker vrug aroma gehad het.
Veroudering van wit wyne op moer is 'n algemene praktyk, alhoewel dit
minder toegepas word op rooiwyne as gevolg van verwante gevare. Hoofstuk
4 bespreek die effek van moerkontak op die mikrobiese en kleursamestelling
van rooiwyn tydens 12 maande se houtveroudering. Geen noemenswaardige
verskille is egter verkry tussen die wyne verouder op die moer en die filtreerde
wyne vir asynsuur-, melksuurbateriee en gisgetalle nie. Aanvanklike pH
verskille tydens koue masserasie en alkoholiese fermentasie het egter hierdie
getalle beinvloed, met hoer ·getalle verkry in die hoer pH wyn. Die wyne wat
appelmelksuurgisting in die vate ondergaan het en verouder is op die moer
het egter 'n laer konsentrasie geelbruin pigmente (gemeet by 420 nm) as die
gefiltreerde wyne. Ander kleurverskille sluit in hoer kleurdigtheid en totale rooi
pigmente as gevolg van langer dopkontak (stadiger alkoholiese fermentasie).
Manipulering van die doppe voor en tydens alkoholiese gisting, die
gebruik van eikehoutvate of eikehoutverwante produkte, of kombinasies
daarvan tydens verskillende produksie fases en ander praktyke soos moer
kontak, kan dus gebruik word am 'n sekere styl wyn op markversoek daar te
stel. Hoofstuk 5 som die resultate op, asook toekomstige
navorsingsmoontlikhede wat op die gebied van hout en wyn gedoen kan
word. Hierdie studie het egter duidelik aangedui dat die eikehout oorsprong
en tipe die kleur nie so baie beinvloed soos die aroma en smaak van die wyn
onder Suid-Afrikaanse kondisies nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50499 |
| Date | January 2005 |
| Creators | Fourie, Benjamin A. |
| Contributors | Du Toit, Wessel J., Stellenbosch University. Faculty of AgricSciences. Dept. of Viticulture & Oenology & Institute for Wine Biotechnology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 139 p. : ill. |
| Rights | Stellenbosch University |
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