Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The winemaking process involves a complex microbial flora where the interaction of
yeasts, lactic acid bacteria and acetic acid bacteria play an important role in the
quality and wholesomeness of the final product. Yeasts are primarily responsible for
alcoholic fermentation. Malolactic fermentation follows alcoholic fermentation and is
conducted by lactic acid bacteria. These bacteria are important in winemaking and
can have a positive or negative effect on the wine quality. Biogenic amines are one
of the compounds produced by lactic acid bacteria, which affect the hygienic quality
and wholesomeness of the wine negatively and directly pose a health risk to the
consumer. The demand of consumers for higher quality and healthier foods has led
to renewed interest in studies on biogenic amines. Biogenic amines occur in a wide
variety of food products, such as cheese, dried sausage, sauerkraut, fishery
products, chocolates, wine and beer. This thesis focussed on the presence of
biogenic amines in wine.
The first objective of the study was to determine the ability of lactic acid bacteria
isolated from South African wine to produce biogenic amines, using a decarboxylase
screening plate method. The potential to produce the biogenic amines histamine,
tyramine, putrescine and cadaverine was investigated. The results obtained showed
that Lactobacillus species (Lactobacillus brevis and Lactobacillus hilgardil) might be
the lactic acid bacteria responsible for tyramine and putrescine production and that it
can contribute significantly to the overall biogenic amine content in wines. The
results also suggest that amine production is strain dependent and not species
specific. None of the lactic acid bacteria tested had the ability to produce histamine
or cadaverine. It is important to remember that the ability of the lactic acid bacteria to
produce biogenic amines has only been investigated in synthetic media and that it
does not necessarily imply similar behaviour in wine. Wine represents a complex
environment with a wide number of factors influencing microbial growth and
decarboxylase activity and, thus, further investigation is necessary to determine if
these amine-producing bacteria behave similarly in wine conditions.
In addition, the polymerase chain reaction (PCR) amplification method was
used for the identification of the tyrosine decarboxylase (TOe) gene in some of the
tyramine-producing lactic acid bacteria. This was followed by the sequencing of the
amplified products, which are partial TOe gene sequences, of two L. brevis strains
and of a L. hilgardii strain. Only one tdc gene sequence has been described for
bacteria (Enterococcus faecalis), while a partial TOC gene sequence from L. brevis
lOEB 9809 was described. An amino acid sequence alignment of the three TOe
gene fragments, obtained in this study, with the known TOe gene fragment of
L. brevis lOEB 9809 and the tdc gene of E. faecalis showed a high degree of
relatedness and conserved regions.
To meet consumer demands, procedures are necessary to prevent the
formation of amines in food products. One way of preventing the formation of biogenic amines is to relate amine production with certain lactic acid bacteria species
involved in the winemaking process. Another possible way would be to develop a
rapid detection method for bacteria carrying amino acid decarboxylase genes. The
results of this study provide knowledge about which lactic acid bacteria in the
winemaking process could contribute to the production of biogenic amines and the
sequencing of additional partial TOe genes could possibly assist in the development
of a rapid detection method for tyramine-producing lactic acid bacteria in food
products. / AFRIKAANSE OPSOMMING: Die wynmaakproses behels 'n komplekse mikrobiese flora waar die interaksie van
giste, melksuurbakterieë en asynsuurbakterieë 'n belangrike rol speel in die kwaliteit
en heilsaamheid van die finale produk. Giste is primêr verantwoordelik vir
alkoholiese fermentasie. Appelmelksuurgisting volg op alkoholiese fermentasie en
word deur melksuurbakterieë uitgevoer. Hierdie bakterieë is belangrik in die maak
van wyn en kan 'n positiewe of negatiewe uitwerking op die kwaliteit van wyn hê.
Biogeniese amiene is een van die komponente wat deur melksuurbakterieë
geproduseer kan word en wat die higiëniese kwaliteit en heilsaamheid van die wyn
benadeel. Dit hou ook 'n gesondheidsrisiko vir die verbruiker in. Die vereiste van
verbruikers vir hoër kwaliteit en gesonder voedselprodukte het nuwe belangstelling in
studies op biogeniese amiene ontlok. Biogeniese amiene kom in 'n wye
verskeidenheid voedselprodukte voor, soos kaas, droëwors, suurkool, vis, sjokolade,
wyn en bier. Hierdie tesis fokus op die teenwoordigheid van biogeniese amiene in
wyn.
Die eerste doelwit van die studie was om melksuurbakterieë, wat uit Suid-
Afrikaanse wyn geïsoleer is, se vermoë te bepaal om biogeniese amiene op
dekarboksilase-agarplate te produseer. Die potensiaal om die biogeniese amiene
histamien, tiramien, putresien en kadawerien te produseer, is bestudeer. Die
resultate wat verkry is, toon dat Lactobacillus-spesies (Lactobacillus brevis en
Lactobacillus hilgardit) vir tiramien- en putresienproduksie verantwoordelik is en dat
hulle 'n belangrike bydrae kan lewer tot die totale biogeniese amienkonsentrasie in
wyn. Die resultate dui ook daarop dat die produksie van amiene afhanklik is van die
ras, en nié 'n spesifieke spesie nie. Geen melksuurbakterieë wat getoets is, het die
vermoë getoon om histamien of kadawerien te produseer nie. Dit is belangrik om in
ag te neem dat die vermoë van die melksuurbakterieë om amiene te produseer slegs
in sintetiese media bestudeer is en dat dit nie noodwendig dieselfde gedrag in wyn
sal toon nie. Wyn is 'n komplekse omgewing met 'n wye verskeidenheid faktore wat
die mikrobiese groei en dekarboksilase-aktiwiteit kan beïnvloed, daarom is verdere
studie nodig om vas te stelof hierdie amien-produserende bakterieë dieselfde
gedrag in wyn sal toon.
Die polimerase-kettingreaksie (PKR) amplifikasie-metode is vir die identifikasie
van die tirosiendekarboksilase-geen (TDK) in sommige van die tiramienproduserende
melksuurbakterieë gebruik. Dit is gevolg deur die volgordebepaling
van die geamplifiseerde produkte, wat gedeeltelike TDK-geenvolgordes is, van twee
L. brevis- en van een L. hilgardii-ras. Slegs een tdk-geenvolgorde is al voorheen vir
bakterieë beskryf, nl. Enterococcus faecalis, asook 'n gedeeltelike TDK-geenvolgorde
vir L. brevis lOEB 9809. 'n Vergelyking van die aminosuurvolgordes van die drie
TDK-geenfragmente wat in die studie verkry is, het 'n hoë graad van ooreenkoms en
gekonserveerde areas met die bekende TDK-geenfragment van L. brevis lOEB 9809
en die tdk-geen van E. faecalis getoon. Om verbruikers se behoeftes te bevredig, is dit noodsaaklik dat die vorming van
amiene in voedselprodukte voorkom word. Een manier van voorkoming is om
amienproduksie aan sekere melksuurbakterieë wat in die wynmaakproses betrokke
is, te koppel. 'n Ander manier sal wees om 'n vinnige metode te ontwikkel vir die
opsporing van bakterieë wat aminosuurdekarboksilase-gene dra. Die resultate van
die studie verskaf kennis van watter melksuurbakterieë in die wynmaakproses tot die
produksie van biogeniese amiene kan bydra. Die volgordebepaling van addisionele
gedeeltelike TDK-gene kan moontlik tot die ontwikkeling van 'n vinnige
opsporingsmetode van tiramien-produserende melksuurbakterieë in voedselprodukte
bydra.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53328 |
| Date | 12 1900 |
| Creators | Downing, Lynn,1978- |
| Contributors | Du Toit, M., Pretorius, I. S., Lambrechts, M. G., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | [xiii], 59 p. : ill. |
| Rights | Stellenbosch University |
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