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.

Thesis (MScAgric)--Stellenbosch University, 1964. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (PhD(Agric) (Viticulture and Oenology))--University of Stellenbosch, 2006. / The winemaking process involves different complex chemical and biochemical reactions, which include those of oxygen (O2). Oxygen can come into contact with the wine through various winemaking procedures and can be used by the winemaker to enhance the quality of red wine. In wine, the main substrates for oxidation are phenolic molecules, which form quinones. These can influence the sensory characteristics of the wine. O2 can be used in fresh must to remove oxidisable phenolic molecules through a process called hyper-oxidation and can also be added to fermenting must to enhance the fermentation performance of yeast. Controlled O2 additions during ageing can lead to the wine’s colour being increased and the astringency of the wine decreased. This is due to the formation of acetaldehyde from the oxidation of ethanol, which induces the polymerisation of tannin and anthocyanin molecules. The addition of too much O2 to wine can, however, lead to unwanted over-oxidation, with certain off-odours being formed. It can also enhance the growth of unwanted spoilage microorganisms, such as Brettanomyces and acetic acid bacteria. Although research on O2 in wine was started many years ago, many questions still remain. These include the general effect of O2 on the sensory and phenolic profile of red wine especially and the microbiology of wine during ageing. An effective way of measuring oxidation, especially in red wine must also be developed. In the first part of this study, the effects of O2 and sulfur dioxide (SO2) additions on a strain of Brettanomyces bruxellensis (also known as Dekkera bruxellensis) and Acetobacter pasteurianus were investigated. Epifluorescence microscopy and plating revealed that the A. pasteurianus strain went into a viable but non-culturable state in the wine after prolonged storage under relative anaerobic conditions. This state, however, could be negated with successive increases in culturability by the addition of O2, as would happen during the transfer of wine when air is introduced. The A. pasteurianus strain was also relatively resistant to SO2, but the B. bruxellensis strain was more sensitive to SO2. A short exposure time to molecular SO2 drastically decreased the culturability of the B. bruxellensis strain, but bound SO2 had no effect on the culturability or viability of either of the two types of microorganisms. Oxygen addition to the B. bruxellensis strain also led to a drastic increase in viability and culturability. It is thus clear that SO2 and O2 management in the cellar is of critical importance for the winemaker to produce wines that have not been spoiled by Brettanomyces or acetic acid bacteria. This study should contribute to the understanding of the factors responsible for the growth and survival of Brettanomyces and acetic acid bacteria in wine, but it should be kept in mind that only one strain of each microorganism was used. This should be expanded in future to include more strains that occur in wine. The second part of this study investigated the effect of micro-oxygenation on four different South African red wines. It was found that the micro-oxygenation led to an increase in the colour density and SO2 resistant pigments of the two wines in which micro-oxygenation was started just after the completion of malolactic fermentation. In one of these wines, a tasting panel preferred the micro-oxygenation treated wines to the control. In the other two red wines, in which the micro-oxygenation was started seven months after the completion of malolactic fermentation, very little colour increase was observed. One of these two wines was also matured in an oak barrel, where the change in phenolic composition was on par with the treated wines. A prolonged period of micro-oxygenation, however, led to this wine obtaining an oxidised, over-aged character. Micro-oxygenation and maturation in an oak barrel also enhanced the survival of acetic acid bacteria and Brettanomyces in this wine. Micro-oxygenation can hence be used by the wine producer on young red wines to enhance the quality of the wine, but should be applied with care in older red wines. Future research into micro-oxygenation should focus on whether it can simulate an oak barrel. More research into the effect of micro-oxygenation on the sensory profile of the wine is needed. As mentioned, the addition of O2 can lead to oxidative degradation of wine. The brown colour in wine is often used as an indication of oxidation, but oxidative aromas can be perceived before a drastic increase in the brown colour has been observed in red wine. The third part of this study was to assess the possible use of Fourier Transform Infrared Spectroscopy (FTIR) to measure the progression of oxidation in Pinotage red wines. Three wines were used in this study and clear separation between the control and aerated wines was observed by using Principle Component Analysis (PCA). Sensory analysis of these wines confirmed this observation, with a reduction especially in berry fruit and coffee characters and an increase first in potato skin and then acetaldehyde aroma characters as the oxidation progressed. PCA analysis also revealed that in certain wines the visible spectrum of light did not indicate the progression of oxidation as sensitively as with the use of FTIR. This also correlated with the inability of the panel to observe a drastic colour change. FTIR should be further investigated as a possible means of monitoring oxidation in wine and this study should be expanded to wines made from other cultivars as well.

Thesis (PhD(Agric) Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2009. / The main goal of this project was to elucidate the underlying genetic factors responsible for the different fermentation phenotypes and physiological adaptations of industrial wine yeast strains. To address this problem an ‘omic’ approach was pursued: Five industrial wine yeast strains, namely VIN13, EC1118, BM45, 285 and DV10, were subjected to transcriptional, proteomic and exometabolomic profiling during alcoholic fermentation in simulated wine-making conditions. The aim was to evaluate and integrate the various layers of data in order to obtain a clearer picture of the genetic regulation and metabolism of wine yeast strains under anaerobic fermentative conditions. The five strains were also characterized in terms of their adhesion/flocculation phenotypes, tolerance to various stresses and survival under conditions of nutrient starvation. Transcriptional profiles for the entire yeast genome were obtained for three crucial stages during fermentation, namely the exponential growth phase (day 2), early stationary phase (day 5) and late stationary phase (day 14). Analysis of changes in gene expression profiles during the course of fermentation provided valuable insights into the genetic changes that occur as the yeast adapt to changing conditions during fermentation. Comparison of differentially expressed transcripts between strains also enabled the identification of genetic factors responsible for differences in the metabolism of these strains, and paved the way for genetic engineering of strains with directed modifications in key areas. In particular, the integration of exo-metabolite profiles and gene expression data for the strains enabled the construction of statistical models with a strong predictive capability which was validated experimentally. Proteomic analysis enabled correlations to be made between relative transcript abundance and protein levels for approximately 450 gene and protein pairs per analysis. The alignment of transcriptome and proteome data was very accurate for interstrain comparisons. For intrastrain comparisons, there was almost no correlation between trends in protein and transcript levels, except in certain functional categories such as metabolism. The data also provide interesting insights into molecular evolutionary mechanisms that underlie the phenotypic diversity of wine yeast strains. Overall, the systems biology approach to the study of yeast metabolism during alcoholic fermentation opened up new avenues for hypothesis-driven research and targeted engineering strategies for the genetic enhancement/ modification of wine yeast for commercial applications.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Yeasts produce a broad range of aroma-active volatile esters and higher alcohols during alcoholic fermentation. Some of these esters and higher alcohols are important for the fruity flavors and therefore the final quality of wine and other fermented beverages. Esters are produced and hydrolyzed by alcohol acetyltransferases and esterases, respectively. In yeast, ester-synthesizing activities are represented by two alcohol acetyltransferases encoded by the ATFI and ATF2 genes, and by an ethanol hexanoyl transferase encoded by the EHTI gene. Atfl p and Atf2p appear responsible for the production of ethyl acetate and isoamyl acetate, while Ehtl p synthesizes ethyl hexanoate from ethanol and hexanoyl-CoA. Although a fair amount of information is available regarding the ATF 1 gene, limited information is available on the remaining alcohol acetyltransferases. Only two genes that code for esterases have been identified in yeast, namely lAHI and TIPI. It has also been shown that the balance between alcohol acetyltransferases and esterases is important for the net rate of ester accumulation. Higher alcohols are synthesized from the a-keto-acids in the branched-chain amino acid metabolic pathway by decarboxylation and reduction. The transamination of the amino acid to the respective a-keto-acid is catalyzed by mitochondrial and cytosolic branched-chain amino acid transferases, which are encoded by the BATI and BAT2 genes, respectively. In recent years, a strong scientific and industrial interest in the metabolism of flavoractive compounds has emerged, but information regarding the roles of specific enzymes and the physiological relevance of their metabolism remains limited. The aim of this project was to investigate the physiological and metabolic consequences of changes in the expression levels of some of the key enzymes involved in aroma compound production. The consequences of these changes on the chemical composition and the fermentation bouquet of wines and distillates were also investigated. The first part of the section on the results in this dissertation reports on the role and relative importance of the Saccharomyces cerevisiae enzymes involved in ester metabolism, namely Atflp, Atf2p, Ehtlp, Iahlp and Tiplp. The corresponding genes were overexpressed in a laboratory strain of S. cerevisiae, BY4742, and in a widely used commercial wine yeast strain, VIN13. Table wine and base wines for distillation were prepared with these VIN13 transformed strains. The ester concentrations and aroma profiles of the wines and distillates were analyzed and compared. The data indicated that the overexpression of ATF 1 and ATF2 increased the concentrations of ethyl acetate, isoamyl acetate, 2-pheylethyl acetate and ethyl caproate, while the overexpression of JAHI resulted in a significant decrease in the concentrations of ethyl acetate, isoamyl acetate, hexyl acetate and 2-phenylethyl acetate. The overexpression of EHTI resulted in a marked increase in the concentrations of ethyl caproate, ethyl caprylate and ethyl caprate, while the overexpression of TJP1 did not decrease the concentrations of any of the esters. In most cases, there was a correlation between the increase in esters and the decrease in higher alcohols. The data suggest that yeast balances the amount of different esters produced through alcohol acetyltransferases and esterases, and that, in some cases, these enzymes appear to overlap in function and/or influence each other's activity. In the second part of the results section, the consequences of the deletion and the overexpression of two genes, BATl and BAT2, which encode transaminases that contribute to the metabolism of higher alcohols, were investigated. The genes were both disrupted in a S. cerevisiae BY4742, and overexpressed in both this laboratory strain and in the VIN13 wine yeast strain. The effects of these modifications on the general physiology of the corresponding yeast strains and on higher alcohol metabolism were assessed in a range of growth conditions, including aerobic and anaerobic growth conditions, in the presence of glucose or raffinose as sole carbon source and growth in the presence of various concentrations of amino acids. Table wine and base wines for distillation were prepared with the modified industrial strains and the concentrations of the higher alcohols and the aroma profiles of the wine and distillates were analyzed and compared. Batl deletion seemed to be lethal under the conditions that were created, and therefore only the bat2!:!.strain, together with the BATI and BAT2 overexpression strains, were investigated. These modifications did not appear to significantly affect the general physiology of the strains. The results obtained indicated that the overexpression of BATI increased the concentrations of isoamyl alcohol and isoamyl acetate, and, to a lesser extent, the concentrations of isobutanol and isobutyric acid. The overexpression of the BAT2 gene resulted in a substantial increase in the levels of isobutanol, isobutyric acid and propionic acid production, and a modest increase in the level of propanol and isovaleric acid. Interestingly, the overexpression of BAT2 led to a decrease in isoamyl alcohol and isoamyl acetate concentrations. Sensory analyses indicated that the wines and distillates produced with the strains in which the BATl and BAT2 genes were overexpressed had more fruity characteristics (peach and apricot aromas) than the wines produced by the wild-type strains. This study offers new prospects for the development of wine yeast starter strains with optimized ester and higher alcohol-producing capability that could assist winemakers in their efforts to consistently produce wine to definable specifications and styles and a predetermined flavor profile. / AFRIKAANSE OPSOMMING: Gedurende fermentasie produseer giste 'n wye verskeidenheid vlugtige aromatiese esters en hoër alkohole. Sommige van hierdie esters en hoër alkohole is belangrik vir die vrugtige geure en dra dus by tot die finale kwaliteit van wyn en ander gefermenteerde drankies. Esters word onderskeidelik deur alkoholasetieltranferases en esterases geproduseer en gehidroliseer. In giste word die ester-sintetiserende aktiwiteite deur twee alkoholasetieltransferases verteenwoordig wat deur die ATFI-en ATF2-gene, asook 'n etanolheksanoïeltransferase wat deur die EHTl-geen, gekodeer word. Dit blyk dat ATFlp en ATF2p verantwoordelik is vir die produksie van etielasetaat en isoamielasetaat, terwyl Ehtl p-etielheksanoaat vanaf etanol en heksanoïel-CoA sintetiseer. Alhoewel daar 'n redelike hoeveelheid inligting t.o.v die ATF I-geen beskikbaar is, is daar weinig inligting oor die res van die aloholasetieltransferases. Slegs twee gene wat vir esterases kodeer, is in gis geïdentifiseer, naamlik IAHI en TIPI. Daar is ook bewys dat 'n balans tussen die alkoholasetieltransferases en esterases baie belangrik is vir die netto-tempo van ester-akkumulasie. Hoër alkohole word gesintetiseer vanaf a-keto sure in die vertakte-ketting aminosuur metaboliese pad deur dekarboksilasie en reduksie. Die transaminasie van die aminosuur na die onderkeidelike a-ketosuur word deur vertakte-ketting aminosuur transferases, geleë in die mitochondrion en sitosol, en gekodeer deur BATl- en BAT2-gene, gekataliseer. In die laaste paar jare het daar 'n sterk wetenskaplike, asook industrïele, belangstelling in die metabolisme van aroma-aktiewe komponente te voorskyn gekom, maar inligting in verband met die rol van spesifieke ensieme en die fisiologiese belangrikheid van hul metabolisme is egter beperk. Die doel van hierdie projek was om die fisiologiese en metaboliese gevolge van veranderinge in die ekspressievlakke van sommige sleutelensieme betrokke by aromakomponent-produksie te ondersoek. Die gevolge van hierdie veranderinge op chemiese vlakke, asook hoe die fermentasie-aroma van die wyne en distillate beïnvloed word, is ook bestudeer. Die eerste gedeelte van die resultate rapporteer oor die rol en relatiewe belangrikheid van die Saccharomyces cerevisiae-ensieme betrokke by estermetabolisme, naamlik Atfl p, Atf2p, Ehtlp, Iahlp en Tiplp. Die gene was ooruitgedruk in 'n laboratoriurnras van S. cerevisiae, BY4742, asook in 'n kommersïele wyngisras, VIN13. Tafelwyne en basiswyne vir distillasie is gemaak met die getransformeerde VIN13-rasse. Die esterkonsentrasies en aromaprofiele van die wyne en distillate is ontleed en vergelyk. Die data het gewys dat die ooruitdrukking van ATFI- en ATF2-gene 'n verhoging in etielasetaat, isoamielasetaat, 2-fenieletielasetaat en etielkaproaat veroorsaak het, terwyl ooruitdrukking van !AHI 'n betekenisvolle afname in etielasetaat-, isoamielasetaat-, heksielasetaat- en 2-fenieletielasetaat-konsentrasies veroorsaak het. Die ooruitdrukking van EHTI het 'n duidelike verhoging in etielkaproaat, etielkaprilaat en etielkapraat veroorsaak en die ooruitdrukking van TIPIhet geen van die esterkonsentrasies verander nie. In die meeste gevalle was daar nie 'n korrelasie tussen die toename in esters en afname in hoër alkohole nie. Die data stelook voor dat die gis 'n balans tussen die verskillende esters handhaaf deur middel van die alkoholasetieltrasferases en esterases, en in sommige gevalle blyk dit dat die ensieme dieselfde funksies het en/of mekaar se aktiwiteit beïnvloed. In die tweede gedeelte van die resultate is die oorsake van delesie en ooruitdrukking van twee gene, BAT1 en BAT2, wat kodeer vir transaminases wat tot hoër alkohol metabolisme bydra, bestudeer. Die gene is uitgeslaan in S. cerevisiae BY4742 en ooruitgedruk in BY4742 en in die wyngisras VIN13. Die effekte van hierdie modifikasies op die algemene fisiologie van die verskillende gisrasse en op hoëralkoholmetabolisme is onder 'n verskeidenheid kondisies bestudeer, naamlik aërobies en anaërobiese groeikondisies, in die teenwoordigheid van glukose of raffinose as die enigste koolstofbron, asook in die teenwoordigheid van 'n verskeidenheid konsentrasies aminosure. Tafelwyne en basiswyne vir distillasie is gemaak met die gemodifiseerde industrïele rasse en die konsentrasies van die hoër alkohole en aromaprofiele van die wyne en distillate is ontleed en vergelyk. Bat1-delesie was dodelik onder die kondisies, daarom is slegs die batlts-tes tesame met die BAT1 en BAT2 wat in die rasse ooruitgedruk is, bestudeer. Die modifikasies het nie 'n beduidende effek op die algemene fisiologie van die rasse getoon nie. Die data het wel getoon dat die ooruitdrukking van BAT1 'n verhoging in isoamielalkohol- en isoamielasetaatkonsentrasies, en tot 'n mindere mate isobutielalkohol- en isobottersuur-konsentrasies, veroorsaak het. Die ooruitdrukking van BAT2 het 'n beduidende toename in isobutanol-, isobottersuur- en propioonsuurkonsentrasies en 'n kleinere toename in propanol- en isovaleriaansuur veroorsaak. Die ooruitdrukking van BAT2 het ook gelei tot 'n afname in isoamielalkohol- en isoamielasetaatkonsentrasies. Sensoriese analises het getoon dat die wyne en distillate wat geproduseer is met die rasse waarin die BAT1 en BAT2 gene ooruitgedruk is meer vrugtige eienskappe (perske- en appelkoos-aromas) getoon het as die wyne wat deur die wildetipe rasse geproduseer is. Die studie lewer nuwe vooruitsigte vir die ontwikkeling van wyngiste met geoptimiseerde ester en hoër alkohol produserende eienskappe wat die wynmakers in staat kan stelom wyne te produseer met gedefinieerde spesifikasies en style en 'n voorafbepaalde aromaprofiel.

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.

Thesis (DScAgric)--Stellenbosch University, 1958. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: During wine fermentation, numerous grape must constituents serve as nutrients to wine yeast (Saccharomyces cerevisiae), which enable their growth and successful completion of alcoholic fermentation. Many of these nutritional factors, in particular nitrogen, also act as precursors for yeastderived flavour compounds such as higher alcohols, esters and volatile fatty acids. Yeast nitrogen metabolism thus plays a determining role in wine aroma and quality. Not only is the nitrogen source, concentration and supplementation timing important, but various environmental factors and the genetic constitution of the yeast strain used for fermentation will also contribute to fermentation outcomes. The main goal of this work was to explore the complex interactions between a number of contributing factors; namely nitrogen source, timing of addition, yeast strain and fermentation matrix. Broadly, this study assessed the impact of seven different nitrogen combinations, added either to the initial grape must or after the onset of fermentation, on fermentation performance and aroma compound production by nine commercial wine yeast strains. Fermentations were done in synthetic grape must, and validated for a subset of parameters in real grape must. The nitrogen treatments were designed according to the generally established order of preference of S. cerevisiae for individual amino acids as source of nitrogen under fermentative conditions, and the potential of certain amino acids to participate in metabolic pathways that produce specific aroma compounds. The results reveal that different nitrogen combinations can lead to unexpected aroma outcomes, depending strongly on the genetic background of individual yeast strains and the timing of nitrogen addition. Certain nitrogen treatments consistently resulted in significant increases or decreases in specific aroma compound concentrations in comparison to the treatment fermented on ammonium as only nitrogen source, for multiple yeast strains. These compounds were classified as nitrogen treatment dependent. Other aroma compounds were produced similarly for all nitrogen treatments and were designated as nitrogen treatment independent. The presence of specific amino acid groups (for example the branched-chain and aromatic amino acids) could be correlated to significantly altered production patterns of related (such as higher alcohols) or unrelated (diethyl succinate) aroma compounds relative to the other nitrogen treatments. Taken together, a number of interesting and novel hypotheses regarding the metabolic pathways involved could be derived from the data. Ultimately, this initial assessment of interactive effects during fermentation will contribute to practical guidelines for winemakers to allow matching grape must constituents (such as nutrients) with the intrinsic aroma production capabilities of specific yeast strains in order to modulate wine aroma, style and quality. / AFRIKAANSE OPSOMMING: Tydens wynfermentasie dien talle druiwemosbestanddele as voedingstowwe vir wyngis (Saccharomyces cerevisiae) wat hul groei bevorder en hul in staat stel om alkoholiese fermentasie suksesvol te voltooi. Baie van hierdie voedingstowwe, veral stikstof, dien ook as voorlopers vir geurkomponente afkomstig van gismetabolisme, soos hoër alkohole, esters en vlugtige vetsure. Die stikstofmetabolisme van gis speel dus ‘n bepalende rol in wynaroma en -kwaliteit. Nie net is die stikstofbron, konsentrasie en tydsberekening van stikstof toevoeging belangrik nie, maar verskeie omgewingsfaktore, asook die genetiese samestelling van die gisras aangewend vir fermentasie, sal bydra tot die fermentasie uitkomste. Die hoofdoel van hierdie werk was om die komplekse interaksies tussen ‘n aantal bydraende faktore te ondersoek; naamlik die stikstofbron, tyd van stikstof toevoeging, gisras en fermentasiematriks. Breedweg het hierdie studie die impak van sewe verskillende stikstofkombinasies, toegedien tot die druiwemos voor of na die aanvang van fermentasie, op die suksesvolle verloop van fermentasie en die produksie van aromakomponente deur nege kommersiële wyngisrasse bepaal. Fermentasies is in sintetiese druiwemos uitgevoer, en ‘n deelversameling van die fermentasies in regte druiwesap te herhaal. Die stikstofbehandelings is ontwerp in ooreenstemming met die algemeen vasgestelde voorkeurvolgorde van S. cerevisiae vir individuele aminosure as stikstofbron onder fermentatiewe kondisies, en die potensiaal van sekere aminosure om mee te doen in metaboliese paaie wat spesifieke aromaverbindings produseer. Die resultate toon dat verskillende stikstofkombinasies tot onverwagte aroma-uitkomste kan lei wat sterk afhanklik is van die genetiese agtergrond van individuele gisrasse en die tyd van stikstof byvoeging. Sekere stikstofbehandelings het konsekwent, vir veelvuldige gisrasse, tot beduidende toenames of afnames in die konsentrasies van spesifieke aromakomponente gelei in vergelyking met die behandeling wat ammonium as enigste stikstofbron bevat het. Hierdie verbindings is as stikstofbehandeling afhanklik geklassifiseer. Ander aromaverbindings is soortgelyk vir alle stikstofbehandelings geproduseer en is aangewys as stikstofbehandeling onafhanklik. Die teenwoordigheid van spesifieke aminosuurgroepe (byvoorbeeld die vertakte-ketting en aromatiese aminosure) kon gekorreleer word met beduidende veranderings in produksiepatrone van verwante (soos hoër alkohole) of onverwante (dietielsuksinaat) aromakomponente relatief tot die ander stikstofbehandelings. Alles inaggenome kon ‘n aantal interessante en nuwe hipoteses rakende die betrokke metabolise padweë van die data afgelei word. Uiteindelik sal hierdie aanvaklike bepaling van interaktiewe effekte tydens fermentasie bydra tot praktiese riglyne vir wynmakers, wat hulle in staat sal stel om druiwesapbestanddele (soos nutriënte) te strook met die intrinsieke aromaproduksie kapasiteite van spesifieke gisrasse, en sodoende wynaroma, styl en kwaliteit te moduleer. / Oenobrands and THRIP for funding this project

Thesis (PhD(Agric))-- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Brandy producers in South Africa can produce three categories of brandy, and within those categories, varies styles in order to cater for diverse consumer needs. Thus they have divergent opinions as to what comprises a good base wine and distillate for their individual end-product style in mind. Due to the fact that brandy is the largest locally produced spirit in South Africa, it is crucial to investigate the factors that influence the production of brandy as better understanding and control of these processes leads to the production of a brandy that is more consistent in quality and in style. The factors known to influence the quality of brandy are the grape cultivar, vinification techniques, distillation and the oak maturation process; however limited research has been done on the factors contributing to the style of brandies. Understanding and identifying the factors that contribute to the style of brandy, will allow for better control and manipulation of the process to ultimately produce a spirit product with a desired style classification. In order to do so, one must distinguish as to what differentiates (chemical and sensory analyses) the two most divergent styles of brandy (in this study referred to as class one and class five three-year barrel matured brandy). Over 104 three-year old barrel matured brandy samples were collected and analysed using GC-FID and HPLC analysis over a three year period. Of these samples, only 7 were classified as a class one three-year barrel matured brandy and 23 were found to be classified as class five three-year barrel matured brandy. The results obtained showed that the class one samples were found to contain a higher concentration of total higher alcohols, higher ratio of higher alcohols vs. esters, higher alcohols vs. acids and aldehydes vs. esters, but a lower level of total esters and acids. The class five samples contained a higher concentration of total esters, furans, lactones and acids, but a lower level of total higher alcohols and ratio of higher alcohols vs. esters. The factors investigated that possibly influence the style of brandy were: the base wine prior to distillation, yeast strain, fermentation temperature, condenser water temperature and barrel age. Results of the base wine analysed prior to distillation show that those samples that scored a sensory score of one could produce a class one three-year barrel matured brandy, and base wines that scored a sensory score of five would yield a class five three-year barrel matured brandy. Alchemy 1 yeast was found to produce elevated levels of total esters and could by default result in a class five three-year barrel matured brandy. Similarly if the wine was fermented at 24⁰C it would result in the increased production of higher alcohols and total acids and in-turn could yield a class one three-year barrel matured brandy. The results obtained show that the different condenser water temperatures do not necessarily influence the concentration of esters and higher alcohols. However, if a lower condenser water temperature (8⁰C) was employed, it could yield a class one barrel matured brandy sample. These distillates are associated with a higher concentration of total higher alcohols and even though they may be positively associated with higher levels of esters, the esters could be removed during the head fraction in the distillation process. The results also show that during the maturation process that the use of 18 year old barrels for the maturation of three-year barrel matured brandy samples could possibly produce a class one three-year barrel matured brandy and the use of new barrels could yield a class five three-year barrel matured brandy sample. It is recommended that analysing the base wine prior to distillation using GC-FID to identify the chemical composition is the most important step in determining the outcome of the style of brandy. / AFRIKAANSE OPSOMMING: Brandewyn produsente in Suid-Afrika kan drie kategorieë brandewyn produseer, en binne hierdie kategorieë sekere style om voorsiening te maak vir die diverse behoeftes van die mark, en dus het hulle uiteenlopende menings oor wat 'n goeie basis wyn en distillaat behels vir hul individuele eindproduk se spesifieke styl. As gevolg van die feit dat brandewyn die belangrikste spiritus produk is wat deur die Suid-Afrikaanse bevolking verbruik word, is dit noodsaaklik dat dié faktore wat die produksie van brandewyn beïenvloed ondersoek word om 'n beter begrip van, en beheer oor hierdie prosesse verkry kan. Dit sal lei tot die produksie van 'n brandewyn van konstante in qualitiet en in style. Die faktore wat bekend is om die gehalte van brandewyn te beïnvloed, is die druifkultivar, wynbereidingstegnieke, distillasie en die hout verouderings proses, maar daar is beperkte navorsing oor die faktore wat bydra tot die styl van n brandewyn. Om die faktore wat bydra tot die spesifieke styl van n brandewyn te identifiseer en te verstaan, kan dit lei tot 'n beter beheer en manipulasie van die prosess om uiteindelik n brandewyn met 'n gewenste styl te produseer. Ten einde dit te kan doen, moet 'n mens kan bepaal wat die twee uiterste style van brandewyn (wat in die studie sal bekend wees as klas een en klas vyf drie-jaar vat veroude brandewyn) van mekaar onderskei (chemiese en sensoriese analise). Meer as 104 drie-jaar vat verouderde brandewyn monsters is ingesamel en ontleed met behulp van GC-FID en HPLC analyliese oor 'n tydperk van drie jaar. Van die 104 monsters, is slegs 7 as 'n klas een drie-jaar vat verourde brandewyn geklassifiseer en 23 as klas vyf drie-jaar vat verourde brandewyn geklassifiseer. Die resultate het getoon dat die klas een monsters 'n hoër konsentrasie van die totale hoër alkohole, 'n hoër verhouding van hoër alkohole teenoor esters het, hoër alkohole teenoor sure en aldehiede teenoor esters, maar 'n laer vlak van totale esters en sure. Die klas vyf monsters het 'n hoër konsentrasie van die totale esters, furanen, laktone en sure, maar 'n laer vlak van totale hoer alkohol en verhouding van hoër alkohole teenoor esters. Die faktore wat ondersoek was wat moontlike ‘n invloed op die styl van brandewyn kon hê, was die basis wyn voor distillasie, die gisras, die fermentasie temperatuur, die kondensor water temperatuur en die vat ouderdom. Die ontledings van die basis wyn voor distillasie het gewys dat die monsters wat 'n sensorise telling van een behaal het, moontlik kan lei tot 'n klas een drie-jaar vat verouderde brandewyn, en basis wyne wat 'n sensorise telling van vyf gekry het weer ‘n klas vyf drie-jaar vat verouderde brandewyn sou oplewer. Alchemie 1 gis ras het ‘n verhoogde vlak van totale esters geproduseer wat tot 'n klas vyf drie-jaar vat verouder brandewyn gelei het As die basis wyn gefermenteer is teen 24⁰C sal dit lei tot die verhoogde produksie van hoër alkohole en totale sure wat 'n klas een drie-jaar vat verouderde brandewyn kan oplewer. Die resultate verkry, toon dat die verskillende kondensor water temperature nie noodwendig die konsentrasie van esters en hoër alkohole beïnvloed het nie, maar dit wil voorkom dat indien 'n laer kondensor water temperatuur (8⁰C) gebruik is, kan dit 'n klas een vat verouderde brandewyn oplewer. Dit hou verband met 'n hoër konsentrasie van die totale hoër alkohole en selfs al word die distillate positief geassosieer met hoër vlakke van esters, kan die esters verwyder word tydens die verwydering van die voorloop in die distillasie proses. Die resultate toon ook dat die gebruik van 18 jaar oue vate vir die veroudering van brandewyn moontlik 'n klas een drie-jaar vat verouderde brandewyn kan oplewer en die gebruik van nuwe vate kan 'n klas vyf drie-jaar vat verouderde brandewyn lewer. Dit word egter aanbeveel dat die basis wyn voor distillasie met GC-FID chemies ontleed word om die samestelling van die wyn te identifiseer Die resultate bly die beste aanduiding van die styl van die brandewyn.

Proefskrif (MScAgric)--Stellenbosch University, 1972. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming