Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The presence and growth of lactic acid bacteria (LAB) in wine and their influence on wine
quality has received much attention in recent years. Lactic acid bacteria are responsible
for conducting malolactic fermentation (MLF) in wine. The benefits associated with
malolactic fermentation in terms of deacidification of wine and the contribution to wine
flavour and complexity have also recently been the topic of research. It is impossible to
describe malolactic fermentation as distinctly desirable or undesirable in terms of its
influence on the final quality of wine. The benefits and disadvantages are dependent upon
viticultural region, grape variety, wine composition, winemaking techniques and the style
and objectives of the winemaker.
Brandy production is a multi-stage process in which base wine production, distillation
technique and wood maturation all have a large influence on the final chemical profile and
organoleptic quality of the brandy. The volatile composition of the base wine, which
basically undergoes a concentration process during the subsequent double distillation
phase, is critical in determining the aroma and flavour quality of the final brandy product.
Thus, the brandy is only as good as the base wine it is distilled from.
The aims of this study were to determine the effect of lactic acid bacteria and
spontaneous malolactic fermentation on the quality of brandy base wine and the resulting
distillate, and to determine which LAB species had been responsible for the occurrence of
spontaneous MLF.
This study showed that LAB are present at high numbers and are able to conduct
spontaneous MLF of brandy base wines. It was shown that the incidence of spontaneous
MLF varied from year to year. In 1998, 50% of the commercially produced base wines had
undergone partial MLF prior to distillation. In 1999 and 2000 respectively, 34% and 45% of
the commercial base wines had undergone partial MLF prior to distillation. The occurrence
of spontaneous MLF had an influence on the chemical composition and the sensory
quality of the base wine and distillate. There was an increase in the concentrations of ethyl
lactate, acetic acid and diethyl succinate in samples that had undergone MLF. There was
also a decrease in the concentrations of esters, such as iso-amyl acetate, ethyl acetate,
ethyl caproate, hexyl acetate and 2-phenethyl acetate in these same samples. Sensory
evaluation of the base wines and distillates demonstrated that samples that had
undergone MLF differed significantly from samples that had not undergone MLF. It was
also shown that distillates that had not undergone MLF had a slightly better aroma profile
than those that had. Sweet aromas, like chocolate and caramel, as well as negative
aromas, like chemical or solvent, were more prominent in brandy distillates that had
undergone MLF. Herbaceous and fruity aromas were more intense in distillates not having
undergone MLF.
Fifty-four strains, all Gram-positive and catalase negative, were isolated at different
stages of brandy production. Seven strains were isolated from the grape juice, 15 strains were isolated from the base wine, 20 strains were isolated during MLF and 12 strains were
isolated from the base wine after MLF had been completed. Based on C02 production
from glucose and gluconate, 17 strains were classified as facultatively heterofermentative
and 37 strains as obligately heterofermentative. Fifteen of the 37 obligately
heterofermentative strains were rod-shaped and were regarded as lactobacilli. The
remaining 22 strains were oval or cocci-bacilli shaped. The isolates were identified to
species level by using numerical analysis of the total soluble cell protein patterns, 16S
rRNAsequencing and polymerase chain reaction (PCR) with species-specific primers.
The facultative heterofermentative lactobacilli were identified as Lactobacillus
paracasei and Lactobacillus p/antarum. The fifteen obligately heterofermentative
lactobacilli were identified as members of the species Lactobacillus brevis, Lactobacillus
verrniforme, Lactobacillus buchneri and Lactobacillus hi/gardii. The 22 obligate
heterofermentative isolates, with a coccoid morphology, could be grouped into two clusters
and were identified as Oenococcus oeni. O. oeni was the species responsible for the
occurrence of spontaneous MLF in most of the commercial base wines. Lb. brevis,
Lb. hi/gardii and Lb. paracasei were also isolated from commercial base wines that had
undergone spontaneous MLF. In nine out of 14 experimental base wine samples that had
undergone spontaneous MLF, O. oeni was again the predominant species. Lb. brevis,
Lb. hi/gardii and Lb. paracasei were identified in the remaining experimental base wine
samples. This is the first report of the presence of Lb. perecese! and Lb. vermiforme in
brandy base wine. It was shown that the occurrence of spontaneous MLF had a negative
effect on the quality of brandy base wine, but that was shown to be due to the different
species and strains performing MLF. In the non-preferred distillate samples, Lactobacillus
spp. had performed MLF or had developed after or during MLF. / AFRIKAANSE OPSOMMING: Die teenwoordigheid en die vermoë van melksuurbakterieë (MSB) om in wyn te groei, is 'n
onderwerp wat al heelwat nagevors is. Melksuurbakterieë is verantwoordelik vir die
uitvoering van appelmelksuurgisting (AMG) in wyn. Die voordele verbonde aan
appelmelksuurgisting, ten opsigte van die verlaging van die totale suurinhoud en die
bydrae tot die verbeterde geur en kompleksiteit van die wyn, is ook al goed bestudeer.
Wat die invloed op die finale wynkwaliteit betref, is dit byna onmoontlik om AMG as
uitsluitlik gewens óf ongewens te beskou. Die voordele en nadele van AMG is afhanklik
van verskeie faktore, nl. wingerdkundige streek, druifkultivar, wynsamestelling,
wynmaakpraktyke, asook die styl en doelwitte van die wynmaker.
Die produksie van brandewyn is 'n multistapproses waarin die bereidingsmetode van
die basiswyn, die distillasietegniek en houtveroudering 'n groot invloed op die finale
kwaliteit en chemiese samestelling van die brandewyn het. Die vlugtige verbindings van
die basiswyn, wat tydens die dubbele distillasieproses gekonsentreer word, is van
wesenlike belang in die bepaling van die aroma en geur van die finale brandewynproduk.
Brandewyn is dus inderdaad net so goed soos die basiswyn waarvan dit gestook is.
Die doelwitte van hierdie studie was om te bepaal wat die invloed van MSB en die
voorkoms van spontane AMG op die kwaliteit van die basiswyn en die distillaat is, asook
om die MSB wat vir die voorkoms van spontane AMG verantwoordelik was, te identifiseer.
Hierdie studie het bewys dat MSB in hoë getalle teenwoordig was en dat dit in staat is
om die spontane AMG van basiswyne uit te voer. Daar is bewys dat die voorkoms van
spontaneAMG moontlik van jaar tot jaar kan verskil. In 1998 het 50%, in 1999 het 34% en
in 2000 45% van die kommersieel-geproduseerde basiswyn gedeeltelike AMG spontaan
voor distillasie ondergaan. Daar is ook gevind dat spontane AMG 'n invloed op die
chemiese samestelling en sensoriese kwaliteit van die basiswyn en die distillaat gehad
het. Daar was 'n toename in die konsentrasies van etiellaktaat, asynsuur en
diëtielsuksinaat in monsters wat spontane AMG ondergaan het. In dieselfde monsters was
daar ook 'n afname in die konsentrasies van iso-amielasetaat, etielasetaat, etielkaproaat,
heksielasetaat en 2-fenielasetaat. Sensoriese evaluering van die basiswyne en distillate
het getoon dat daar betekenisvolle verskille was tussen die monsters wat AMG ondergaan
het en dié wat nie AMG ondergaan het nie. Daar is bewys dat die distillate wat nie AMG
ondergaan het nie, 'n beter aromaprofiel gehad het as dié wat AMG ondergaan het. Soet
geure, soos sjokolade en karamel, en negatiewe geure, soos "chemies" en "oplosmiddel",
was prominent in distillate wat AMG ondergaan het. Kruidagtige en vrugtige geure was
meer intensief in distillate wat nie AMG ondergaan het nie.
Vier-en-vyftig bakteriese rasse, almal Gram-positief en katalase-negatief, is gedurende
die verskillende stadia van brandewynproduksie geïsoleer. Sewe rasse is uit druiwesap,
15 rasse gedurende die alkoholiese fermentasie, 20 rasse gedurende AMG en 12 rasse
na voltooiing van AMG geïsoleer. Op die basis van koolstofdioksied (C02)-produksie vanaf glukose en glukonaat is 17 rasse as fakultatief heterofermentatief en 37 rasse as obligaat
heterofermentatief geklassifiseer. Vyftien van die 37 obligaat-heterofermentatiewe rasse
was staafvormig en is as lactobacilli geïdentifiseer. Die oorblywende 22 het ovaal of
kokkus-bacillusvormige selmorfologie getoon. Identifikasie tot op spesievlak is gedoen
deur van numeriese analise van die totale oplosbare selproteïenprofiele, 16S-rRNAvolgordebepalings
en spesie-spesifieke inleiers vir die polimerasekettingreaksie (PKR)
gebruik te maak.
Die fakultatief-heterofermentatiewe rasse is as Lactobacillus paracasei en
Lactobacillus p/antarum geklassifiseer. Die 15 obligaat heterofermentatiewe stafies is as
Lactobacillus brevis, Lactobacillus buchneri, Lactobacillus hi/gardii en Lactobacillus
vermiforme geïdentifiseer. Die 22 ovaal, obligaat heterofermentatiewe isolate kon in twee
groepe ingedeel word en is as Oenococcus oeni geïdentifiseer.
Daar is bevind dat O. oeni-isolate vir die voorkoms van spontane AMG in die meeste
van die kommersiêle basiswyne verantwoordelik was. Lb. brevis, Lb. hi/gardii en
Lb. paracasei is ook uit kommersiêle basiswyne wat spontane AMG ondergaan het,
geïsoleer. In nege uit 14 van die eksperimentele basiswyne wat spontane AMG ondergaan
het, was O. oeni die dominante spesie. In die oorblywende eksperimentele wyne is
Lb. brevis, Lb. hi/gardii en Lb. paracasei aangetref. Hierdie is die eerste vermelding van
die teenwoordigheid van Lb. paracasei and Lb. vermiforrne in brandewynbasiswyn. Daar is
gevind dat die voorkoms van spontane AMG "n negatiewe invloed op brandewynkwaliteit
het, maar dit is as gevolg van die verskeidenheid van MSB-spesies en rasse wat voorkom.
In die distillate wat deur die proepaneel afgekeur is, het Lactobacillus spesies die AMG
deurgevoer, of het dit tydens of na AMG ontwikkel.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53161 |
| Date | 12 1900 |
| Creators | Du Plessis, Heinrich Wilbur,1975- |
| Contributors | Lambrechts, M. G., Du Toit, M., Pretorius, I. S., Stellenbosch University. Faculty of AgriSciences. Dept. of Viticulture and Oenology and Institute for Wine Biotechnology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 89 p. : ill. |
| Rights | Stellenbosch University |
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