Dissertation (PhD (Agric))--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (MScAgric)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Ferdinand de Lesseps grapes have a distinctive fruity varietal character and were often used judiciously by wine-makers to enhance the fruity bouquet of some white table wines. Ferdinand de Lesseps grape juice was investigated to identify the main contributing compounds responsible for its unique and intense aroma. The juice was recovered from grapes under anaerobic conditions and extracted using Freon 11. The concentrated extract was analysed using a combination of capillary gas chromatography-mass spectrometry and gas chromatography-sniffing techniques. Thirty-two compounds were reported. With the aid of GC-sniffing, it was concluded that the hybrid note of the Ferdinand de Lesseps grape was most likely attributed to the presence of 2,5-dimethyl-3(2H)-furanone and 0- aminoacetophenone. Esters, which featured prominently in the juice, consisted mainly of ethyl butanoate, ethyl- and methyl- 3-hydroxy butanoate, and to a lesser extent, ethyl 3- hydroxy hexanoate and ethyl-3-hydroxy propanoate. These esters are most likely responsible for the sweetish pineapple aroma. According to EEC regulations, the use of non- Vinifera grapes in the production of commercial wines is prohibited. The presence of 2,5-dimethyl- 3(2H)-furanone in wine could therefore be interpreted as a labrusca indicator should it be suspected that Ferdinand de Lesseps grapes were used in the blend. The quality of some South African Kerner table wines often is rated inferior owing to an unwanted odour described as "Elastoplast" or "medicinal". This odour is encountered occasionally in wines from other cultivars such as Gewurztraminer, Weisser Riesling, Muscat de Frontignan and Chenin blanc. The identification of the compounds responsible for the offodour was investigated, as well as possible relationships between its occurrence and viniviticultural practices. The compound responsible for the "medicinal" off- odour was identified as p-vinyl guaiacol. It is formed via decarboxylation of ferulic acid by yeast during alcoholic fermentation. lts concentration is directly related to the concentration of ferulic acid and the yeast strain. Other factors affecting p-vinyl guaiacol formation in Kerner wines are region, microclimate, exposure of grapes to sunlight and grape maturity. Wines made from grapes harvested from the warmer climatic regions and exposed to direct sunlight and increased maturity contained higher levels of p-vinyl guaiacol. Viticultural practices that can be applied to limit the formation of the p-vinyl guaiacol precursor in grapes are the use of a canopy manipulation to protect the grapes from direct sunlight and an earlier harvesting date. Various winemaking techniques can be used to lower p-vinyl guaiacol levels in wine. Careful consideration must be given to the choice of yeast, as different yeast strains differ considerably with their ability to form p-vinyl guaiacol. Fining oxidised grape juice with phenol adsorbing agents such as activated charcoal, polyvinylpolypirrollidone, casein, gelatin (particularly in combination with bentonite and "kieselsol") led to decreases in the p-vinyl guaiacol levels. Although fining with activated charcoal was the most effective must treatment for reducing the "medicinal" aroma of Kerner wines, it stripped the wines of colour and character. Excessive oxidation of must followed by fining involves extra costs and time for the winemaker and would not be used in making the reductive style of wines. / AFRIKAANSE OPSOMMING: Ferdinand de Lesseps druiwe en wyne vertoon unieke vrugtige varieteitskarakter en is dikwels deur wynmakers in versnitte gebruik om die geur van sekere wit tafelwyne te verbeter. In hierdie studie is Ferdinand de Lesseps druiwe ondersoek om die belangrikste komponente wat verantwoordelik is vir die prominente, unieke aroma daarvan te identifiseer. Die sap is onder anaerobe toestande herwin en met Freon 11 ekstraheer. Die gekonsentreerde ekstrakte is met behulp van 'n kombinasie van kapillêre gaschromatografie-massaspektrometrie en gaschromatografie-snuif tegnieke analiseer. Twee-en-dertig komponente is gerapporteer. Met die behulp van GC-snuiftegnieke is bevestig dat die hibried karakter in Ferdinand de Lesseps druiwe hoofsaaklik aan die teenwoordigheid van o-amino-asetofenoon en 2,5-dimetiel-3(2H)- furanoon toegeskyf kan word. Die vernaamste esters in die sap was etielbutanoaat, etiel- en metiel-3-hidroksibutanoaat en in 'n mindere mate etiel-3-hidroksiheksanoaat en etiel-3- hidroksipropanoaat. Dié esters is waarskynlik verantwoordelik vir die soet pynappel aroma. Volgens EEG regulasies word die gebruik van nie- Vinifera druiwe vir die produksie van komersiéle wyne verbied. Die teenwoordigheid van 2,5-dimetiel-3(2H)-furanoon in wyn kan dus interpreteer word as 'n labrusca indikator in gevalle waar gebruik van Ferdinand de Lesseps druiwe vermoed word. Die kwaliteit van sommige Suid-Afrikaanse Kerner wyne word dikwels verlaag vanweë die teenwoordigheid van 'n geur wat beskryf word as "Elastoplast" of "medisinaal". Dié reuk word soms waargeneem in wyne van ander kutivars soos Gewurztraminer, Weisser Riesling, Muskaat de Frontignan en Chenin blanc. Die identiteit van die komponent wat vir dié ongewenste reuk verantwoordelik is, asook moontlike verwantskappe met wingerd- en wynkundige praktyke is ondersoek. Die komponent wat vir die medisinale karakter verantwoordelik is, is geïdentifiseer as para-vinielguajakol. Dit word deur dekarboksilasie van feruliensuur deur gisselle tydens alkoholiese gisting gevorm. Die konsentrasie van paravinielguajacol in wyn is direk verwant aan die konsentrasie feruliensuur en die gisras. Ander faktore wat para-vinielguajacol-vorming in Kerner wyn affekteer is streek, mikroklimaat, blootstelling van druiwe aan direkte sonlig en die rypheidsgraad van die druiwe. Wyne wat berei is van ryper druiwe uit warmer streke en wat direk aan sonlig blootgestel was, het hoër konsentrasies para-vinielguajacol bevat. Lowerbestuurspraktyke met behulp waarvan druiwe teen direkte sonligblootstelling beskerm word, is van die vernaamste wingerdkundige praktyke wat aangewend kan word om die vorming van die voorlopers van paravinielguajacol in druiwe te verlaag. Verskeie wynbereidingstegnieke kan gebruik word om die para-vinielguajacol vlakke in wyn te verlaag. Gisraskeuse is van besondere belang omdat gisrasse grootliks verskil in hul vermoë om para-vinielguajacol te vorm. Breibehandelings van geoksideerde sap met middels soos geaktiveerde koolstof, PVPP, kasseïen, gelatien (veral in kombinasie met bentoniet en "kieselsol") het die vlakke van para-vinielguajacol in wyne verlaag. Hoewel geaktiveerde koolstof die doeltreffendste breimiddel vir die verlaging van para-vinielguajacol was, het dit te veel kleur en geur uit die wyn verwyder. Oormatige oksidasie van mos gevolg deur breibehandelings sal meer geld en tyd verg en word nie aanbeveel vir wyne wat in 'n reduktiewe styl berei word nie.

An objective method to blend wines for standardizing flavor quality was developed. Aroma volatiles of varietal and white stock wines were analyzed at 6°C and 37°C by headspace gas chromatography with cryofocussing. Pattern similarity constants of the chromatographic profiles were entered into the simplex optimization program which determined the best blending ratios of wines to simulate the target wine. Thirteen and 23 vertices were required to give the optimum response for trials 1 and 2, respectively. For both trials the computer optimized blends could not be differentiated from the target wines by a sensory taste panel consisting of both untrained and expert judges. / Land and Food Systems, Faculty of / Graduate

This is a study of wine in antiquity. An attempt to describe the spatial diffusion of winemaking in ancient times and to acknowledge the principal factors which spurred that diffusion has produced a study which is simple in structure, but wide-ranging in temporal and geographical compass as well as in its topical diversity. Basically, it consists of two sections, corresponding to the dual preoccupation of diffusion and function. Part I traces winemaking's diffusion from its likely beginnings to the end of the Roman Empire. Although casual Palaeolithic fermentation was probably practised, organised winemaking awaited the systematic viticulture which arrived with the Neolithic, From a generally agreed origin in Armenia, winemaking's story is followed through a series of lands: Babylonia and Assyria, Egypt, Anatolia, Persia, the Levant, Greece, Italy, and the Roman Empire in Africa and Europe. The oenological variety of these lands is made apparent. Major patterns of wine trading and their influence or lack of it on winemaking's spread are studied. What emerges from this account is the startling vigour of this diffusion story, indicative of the high esteem in which ancient man held wine. Part II attempts to identify the reasons for such esteem in order to understand the diffusion momentum of winemaking. The utility of wine to the ancients is examined systematically in some detail. The following themes are treated: wine for the body, that is, wine as liquid, wine as food, wine as medicine (and aphrodisiac); wine for recreational drinking--its value to the individual and its role in society; wine for religious observance and man's existential well-being. An endeavour is made to avoid mere cataloguing of examples in favour of assessing wine's role in these various domains. At every turn, the great importance of the beverage in ancient life becomes apparent. A wide range of writing—ancient and modern, primary and interpretative—has been culled for information, including materials drawn from the biological, medical, and social sciences, technology, archaeology and epigraphy, art history, classical literature, linguistics, comparative religion, and Biblical exegesis. Even so, it would be unwise to consider the present examination more than an introduction to a rich and complex theme in the history of Western man. / Arts, Faculty of / Geography, Department of / Graduate

Thesis (MTech (Food Technology))--Cape Peninsula University of Technology, 2018. / Port is a wine style that comes from Portugal. It is a sweet fortified dessert wine that is made in red and white styles. The taste is a balanced and complex combination of berry fruit, acidity, sweetness, alcohol and tannins. The taste should be sweet, smooth, complex, with some spiciness and a dry finish, but not astringent (Anon., 2009). There are a variety of port types in terms of flavour intensity, aroma and sweetness levels. Young immature ports can be fruity, simple, coarse, spicy and astringent. The sweetness results from the natural grape sugar in the wine, while wine spirits is added to fortify and ensure microbiological stability during aging (Anon., 2009). In this study the work was done on the ruby port style wine, ruby port wine is well known for its characteristic of being bright red in colour and therefore also very difficult to preserve in terms of colour stability in general. Colour is one of the principle parameters of the quality of not only port wine but also red wine in general, since it is the first characteristic to be perceived by the consumer in the glass. The colour of port wine also gives an indication of possible defects, the body, age and the evolution of the wine during storage. Colour, therefore, has an important influence on the overall acceptability of the product to the consumer. During aging, the wine colour changes, mainly due to progressive structural changes of anthocyanins. These changes are often perceived as undesirable by port consumers. As a result, the Cape Port Producers Association (CAPPA) requested this type of research to be done on port wine to improve the port wine making process in order to also give port wine a more stable colour. Therefore the objective of this study was to manipulate some of the parameters in port wine making, such as type of spirit used to fortify, storage temperature and also storage time in order to improve optimum stability of port wine colour. From the first part of the study it was evident that the type of fortifying spirits, storage time and temperature had a significant effect on the colour of the port wine samples. The 96.5% (v.v-1) fortifying spirits, shorter storage time and storage temperature below 25oC resulted in a more stable ruby port colour as well as the lowest change over time. As the study progressed the design variables differed in terms of two types of cultivars used the spirits used to fortify the port wine samples with, addition of a pectolytic enzyme to some of the port wine samples, as well as storage time of 12 months and only two storage temperatures. It could be concluded that at the end of this part of the study, that port wine colour stability was affected by the interaction of the design variables in each treatment and less so by individual design variables in the study. It could also be concluded in this study that higher levels of acetaldehyde present in the spirits used to fortify port wine, did have a significant impact on ruby port wine and colour stability. The application of pectolytic enzyme preparation does not necessarily have a significant effect on its own but depends on the type of cultivar used. Storage time and temperature should also be kept to a minimum to ensure the desirable bright red colour of a ruby port wine.

Thesis (M.S. in food science)--Washington State University, August 2008. / Includes bibliographical references (p. 80-88).

Thesis (M.Ec.(Rsch.))--University of Adelaide, Dept. of Economics, 2001. / Includes bibliographical references.

Low nitrogen Chardonnay juice from an Oregon winery was fermented with a series of nutrient supplements, including diammonium phosphate (DAP), Fermaid K, Superfood, yeast extract, yeast hulls and thiamine. These treatments were evaluated for their contribution to the yeast assimilable nitrogen content (YANC) of the juice, which consists of the ammonium ion and α-amino acid content by NOPA (nitrogen by ophthaldialdehyde). The fermentation characteristics and the nutritional and chemical status of the finished wines were compared. Diammonium phosphate added 25 mg N/L from ammonia for every pound/1000 gallons (12.5 g/hL) used. Commercial yeast nutrient preparations were found to contribute around 10 mg N/L from ammonium ion per pound/1000 gallons (12.5 g/hL). NOPA and HPLC analysis of Superfood and Fermaid K indicated that they contributed only a small amount of amino acids. NOPA analysis of PL-50 yeast extract indicated that it may have added some nitrogen from amino acids. Nitrogenous compounds were taken up within the first few days of fermentation. Ammonium ion was depleted very quickly and did not reappear later in fermentation. Alpha-amino acids reached a low within approximately ten days of fermentation, then leveled out or increased towards the end of fermentation. Treatments containing high amounts of ammonia were observed to produce the most vigorous fermentations. These treatments were found to have the highest apparent levels of amino acids at the end of fermentation. The Control treatment, which had the lowest YANC content, appeared to utilize proline during fermentation. Sensory analysis was not conducted on the finished wines due to replication differences in reduced sulfur aroma found in preliminary screening. GC-MS analysis showed that the higher nitrogen treatments had levels of reduced sulfide compounds that were above sensory threshold, whereas moderate nitrogen treatments did not. Ethyl carbamate was not found in any of the finished wines. These data suggest that moderate levels of supplementation had a positive effect on both fermentation and finished wine quality. Higher levels of nutrient addition were effective at increasing fermentation rates but negatively affected the sulfide profile of finished wines. / Graduation date: 2001