Dissertation (PhD)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Brandy production is a multi-step process that involves grape harvesting, base wine
fermentation, distillation, wood maturation and blending. Within each of these production
process steps there are a number of factors that can influence the composition and
resultant quality of the base wine, unaged and wood matured distillates. These factors
include geographic and climatic features of the origin of grapes used, viticultural practices,
grape maturity, grape variety, vintage variation, vinification techniques, storage of the base
wine prior to distillation, distillation technique, age and origin of oak wood used for
maturation and barrel toasting levels.
The composition of flavour is extremely complex in wine and distilled beverages such
as brandy. A multitude of compounds can take part in the formation of flavour, and it is
rare that a particular compound, that is solely responsible for nuances of a specific flavour,
is identified. Thus, taking brandy production factors and the nature of aroma and flavour
into account, it is clear that thorough understanding of the complexities affecting the
perception of quality in brandy is difficult.
In commercial brandy production, standard operating procedures do not allow for the
separate distillation of brandy base wines from different producers and mixing of base
wines from different regions and producers thus occurs. This makes it difficult to determine
whether the quality determination of the base wine is in fact an indication of the quality of
the resultant distillate after the required period of wood maturation. Therefore, the aim of
this study is to determine whether there is any merit in storing and distilling brandy base
wines from different producers and regions separately. This was done by firstly
determining the demographic and production factors that influence brandy base wine
composition. Secondly, the influence of brandy base wine composition on the quality of the
respective unaged potstill distillates as well as the ultimate style and quality of the threeyear
old wood matured potstill distillates was determined.
For this purpose, four potstills with a capacity of 2000 L each were isolated and used
for commercial scale distillations of 33 and 25 brandy base wines in 1999 and 2000,
respectively, at the DisteIl distillery in Worcester. The experimental outlay used in the
study closely emulated Distell's standard operating procedures for commercial brandy
production.
Chenin blanc and Colombar are the two most popular grape varietals used in the
making of brandy base wine in South Africa. Due to the complexity of the brandy
production process, the first part of the study only focussed on South African young
Chenin blanc wines, with a predominantly fermentation derived aroma. The concentration
of iso-amyl acetate, hexyl acetate, ethyl caprylate, ethyl caprate, 2-phenethyl acetate and
octanoic acid was significantly higher in wines awarded gold and silver medals and
decreased significantly with subsequent decreases in quality categories. Ethyl lactate
exhibited the opposite pattern. A quality predictor model based on the behaviour of 21 volatile compounds quantified in these wines had a resonable prediction accuracy when
having to predict the quality of wines made in the same vintages as it had been trained on.
It was significantly poorer when tested on a completely different vintage of wines to the
ones it had been trained on. The number of vintages, number of wines per vintage and the
number of compounds quantified for the model influence its prediction accuracy.
Twenty-seven volatile compounds were quantified in 33 and 25 brandy base wines,
their unaged and three year old distillates from 1999 and 2000, respectively. ANOVA and
CART analysis showed that vintage, region, harvest time, choice of cultivar and yeast
strain can have a significant influence on the volatile compound composition of brandy
base wines, their unaged and three year old distillates. These factors as well as the
volatile compound composition were also found to influence the sensory quality of these
products. Base wines, unaged and three year old distillates originating from the De Dooms
region, which predominantly cultivates table grapes, were of significantly lower quality than
those from the remaining regions. Products made from grapes harvested early in the
season were of significantly higher quality. The volatile aroma compound composition was
found to differ significantly between the 1999 and 2000 base wines and distillates,
irrespective of the exclusion of those samples that had undergone partial or complete
malolactic fermentation. Consequently, quality indicating compounds may vary from
vintage to vintage. The relationship between the quality of brandy base wines and the
concentration of n-butanol, iso-amyl acetate, ethyl lactate, ethyl caprylate, octanoic- and
decanoic acid was the same as that reported in young Chen in blanc wines in this study. In
unaged distillates, increased levels of ethyl lactate also exert a negative influence on
distillate quality. Iso-amyl acetate, hexyl acetate, ethyl caproate, ethyl caprylate, n-butanol,
octanoic acid, ethyl caprate and decanoic acid showed some positive correlation, whilst
iso-butanol, ethyl lactate, acetic acid, acetaldehyde and ethyl acetate showed a significant
negative correlation to three-year old distillate quality.
Sensory descriptive analysis on selected good, average and poor quality distillates
using the South African brandy aroma wheel showed that there are small differences in
profile between the good and average distillates, there were however significant
differences between the good and poor quality distillate profiles throughout maturation.
After three years of wood maturation, the aroma profile of poor quality distillates can be
characterised by prominent herbaceous and woody aromas, which are more intense than
the fruity aromas. Good quality distillates contained characteristically intense fruity aromas.
Volatile compound concentration differences were noted during the course of and after
three years of wood maturation and in barrels of varying ages. Distillates matured in new
block barrels exhibited significant differences in volatile and wood compound composition
after three years when compared to remaining barrels used. The style classification of the
three-year old potstill distillate was influenced by demographic and production factors and
volatile compound composition, but not by the sensory quality of the distillates.
In summary, vintage, region, cultivar, harvest time and choice of yeast strain have a
significant influence on the volatile composition of brandy base wines, their unaged and three year old potstill distillates, which in turn affects the sensory quality of these products.
These effects cannot be viewed in isolation as they jointly exert an influence on the
composition and quality of these products. From a commercial perspective, this study has
provided a valuable indication as to which production and demographic factors can
influence the quality and style of potstill brandy. Thus, future brandy base wine intake
should, as far as possible, take place in such a manner to allow base wines originating
from the same cultivar or region or harvest time or combination thereof (and to a lesser
extent yeast strain) to be received simultaneously at the distillery for distillation. / AFRIKAANSE OPSOMMING: Brandewyn produksie is 'n veelvoudige proses wat die volgende insluit: pars van druiwe,
basiswyn fermentasie, verstoking, houtveroudering en versnyding. Binne hierdie stappe is
verskeie faktore wat 'n invloed op die samestelling en resultate van die basiswyn,
onverouderde en verouderde distillaat kan hê. Hierdie faktore sluit die volgende in:
geografiese ligging, klimaat toestande van die streek van herkoms, wingerdboupraktyke,
graad van rypheid, druifvarieteit, wynoes variasie, wynbou tegnieke, opberging van
basiswyn voor distillasie, distillasie tegnieke, ouderdom en oorsprong van akkerhout vir die
veroudering, asook tot watter mate die vat gerooster is.
Die samestelling van geur in wyn en gedistilleerde produkte soos brandewyn is uiters
kompleks. 'n Menigte samestellings kan deel vorm van die inhoud van die geur, en dit is
raar dat 'n bepaalde verbinding alleenlik verantwoordelik is vir 'n kenmerkende geur.
Weens die verskeidenheid van produksie faktore, aroma en smaak is volledige kennis van
brandewyn ingewikkeld en kompliseerd om te verstaan.
In kommersiële brandewynproduksie, maak standaard werksprosedures nie
voorsiening vir aparte distillasie van basiswyn van verskillende produsente nie, en die
vermenging van basiswyn van verskillende streke en produsente kom voor. Dit maak dit
moeilik om te bepaal of die kwaliteit van die basiswyn of die distillaat na die neergelegde
periode van houtveroudering, in werklikheid 'n beslissende indikasie op die kwaliteit van
die verouderde produk is. Daarom is een van die doele van hierdie studie om te bepaal of
daar meriete in is om brandewyn basiswyn van die verskillende produsente en streke
apart te berg en te verstook. Dit is gedoen deur eerstens, die effek van demografiese en
produksie faktore op die samestelling van brandewyn basiswyn te bepaal. Daarna, om die
invloed van brandewyn basiswynsamestelling op die kwaliteit van onderskeidelik die
onverouderde distillate sowel as die uiteindelike styl en kwaliteit van die 3 jaar oue
houtverouderde potketel distillate, te bepaal.
Vir hierdie doel, is vier potketels met 'n kapasiteit van 2000 liters elk geïsoleer en vir
kommersiële skaal distillasies van 33 en 25 brandewyn basiswyne in 1999 en 2000,
ondeskeidelik, by DisteIl Distillerdery, Worcester verstook. Die eksperimentele uitleg wat
in hierdie studie gebruik is, ewenaar DisteIl se standaard verstokingsprosedures vir
kommersiële brandewynproduksie.
Chenin blanc en Colombar is die twee mees populêre druifvarieteite vir die maak van
brandewyn basiswyn in Suid-Afrika. As gevolg van die kompleksiteit van die brandewyn
produksieproses, is die eerste gedeelte van die studie gefokus op die Suid-Afrikaanse jong
Chenin blanc wyne, met 'n oorheersende fermentasie geur. Die konsentrasie van iso-amyl
asetaat, heksiel asetaat, etiel kaprilaat, etiel kapraat, 2-phenetiel asetaat en oktanoë suur
was aansienlik hoër in wyne wat met goud en silwer medaljes bekroon is en neem
aansienlik af met afname in kwaliteit kategorieë. Etiel laktaat vertoon die teenoorgestelde
patroon. 'n Kwaliteit voorspellersmodel, gebaseer op die gedrag van 21 vlugtige komponente was opgestel. Die model het redelike akkuraatheid getoon op wyne van
dieselfde oesjaar as waarop oorspronklik opgelei. Die model se voorspellingsakkuraatheid
was aansienlik swakker toe dit vergelyk getoets is met wyne van 'n nuwe oesjaar. Die
hoeveelheid oesjare, hoeveelheid wyne per oesjaar en die hoeveelheid verbindings
gebruik in hierdie model sal die voorspellingsakkuraatheid beïnvloed.
Sewe-en-twintig vlugtige komponente was gekwantifiseer in 33 en 25 brandewyn
basiswyne, die onverouderde en 3 jaar oue distillate vanaf 1999 en 2000, onderskeidelik.
Variasie ontledings (ANOVA) en klassifikasie en regressie ontledings (CART) ontledings
wys dat oesjaar, streek, parstyd, keuse van kultivar en gisrasse In aansienlike invloed op
die vlugtige samestelling van brandewyn basiswyne asook hul onverouderde en 3 jaar
distillate het. Hierdie faktore, sowel as die vlugtige verbinding samestellings, beinvloed
ook bevind die sensoriese kwaliteit van hierdie produkte. Basiswyne, onverouderde en 3
jaar oue distillate wat vanuit die De Doorns streek, wat hoofsaaklik tafeldruif kultivars is, is
van In swakker kwaliteit as die ander streke. Produkte wat gemaak is van druiwe wat
vroeg in die seisoen gepars is, was van beter kwaliteit. Die vlugtige
geurkomponentsamestellings het tussen die basiswyne en distillate van die 1999 en 2000
oesjare verskil, ongeag of party van die monsters gedeeltelike of volledige
appelmelksuurgisting ondergaan het. Gevolglik, die konsentrasie van kwaliteitaanwysende
komponente mag van seisoen tot seisoen verskil. Die verhouding tussen die kwaliteit van
die brandewyn basiswyne en die konsentrasie van n-butanol, iso-amiel asetaat, etiel
laktaat, etiel kaprilaat, oktanoë- en dekanoë suur was dieselfde soos gerapporteer oor die
jong Chenin blanc wyne. In onverouderde distillate, het verhoogde vlakke van etiel
laktaat In negatiewe invloed op distillaat kwaliteit veroorsaak. Iso-amiel asetaat, heksiel
asetaat, etiel kaproaat, etiel kaprilaat, n-butanol, oktanoë suur, etiel kapraat en dekanoë
suur In positiewe korrelasie, terwyl iso-butanol, etiel laktaat, asynsuur, asetaldehied en
etiel asetaat betekenisvolle negatiewe korrelasie met 3jaar oue distillaat kwaliteit bewys.
Beskrywende sensoriewe analises op geselekteerde, middelmatige en swak kwaliteit
distillate (gedoen deur gebruik making van die Suid-Afrikaanse Brandewyn Aromawiel)
wys dat daar klein verskille tussen die profiele van goeie en middelmatige distillate is.
Daar is egter aansienlike verskille tussen goeie en swak kwaliteit distillataat profiele
regdeur die drie jaar verouderingsperiode. Na 3 jaar van houtveroudering kan die geur
profiel van swak kwaliteit distillate uitgeken word aan kruid- en houtagtige geure, wat meer
intens as die vrugagtige geure is. Goeie kwaliteit distillate het intense vrugagtige-aroma
eienskappe.
Vlugtige verbinding konsentrasie verskille is waargeneem gedurende en na die 3jaar
houtverouderingsperiode in vate wat van ouderdomme verskil. Distillate wat in nuwe
blokkies vate verouder is, vertoon aansienlike verskille in vlugtige en houtkomponent
samestellings na 3 jaar wanneer dit met die, wat in die oorblywende ouer vate verouder is,
vergelyk word. Die styl klassifikasie van die 3 jaar oue potketeldistillaat was deur
demografiese en produksie faktore sowel as vlugtige verbinding samestellings beïnvloed,
maar nie met die sensoriese kwaliteit van die distillate nie. In opsomming, oesjaar, streek, kultivar, parstyd en keuse van gisrasse het 'n
aansienlike invloed op die vlugtige komponent samestelling van die brandewyn basiswyne,
onverouderde en 3 jaar oue potketel distillate, wat weer op hul beurt die sensoriese
kwaliteit van die onderskeidelike produkte beïnvloed. Die effek van hierdie faktore kan nie
in isolasie gemeet word nie, aangesien dit gesamentlik die kwaliteit van die produkte
beïnvloed. Van 'n kommersiële perspektief het hierdie studie 'n waardevolle indikasie
gelewer van hoe produksie en demografiese faktore die kwaliteit en styl van
potketelbrandewyn kan beïnvloed. Daarom word voorgestel dat toekomstige brandewyn
basiswyn innames, sover as moontlik, voorsiening moet maak om wyne van dieselfde
kultivar, uit dieselfde streek, parsseisoen inaggeneem, of kombinasie daarvan, met 'n
mindermate die gisrasse in aanmerking geneem, gelyktydig vir verstoking by die
distilleerderye ontvang word sodat hierdie wyne apart van wyne met ander bogenoemde
variasies verstook en verouder kan word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53770 |
| Date | 03 1900 |
| Creators | Snyman, Caroline Lucie Charlotte |
| Contributors | Lambrechts, M. G., Du Toit, M., Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and 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 | 290 p. : ill. |
| Rights | Stellenbosch University |
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