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

The overall purpose of this study was to develop sensory evaluation methodology whereby wine quality can be predicted from juice quality. Descriptive analysis was used by a trained panel to describe Pinot noir juice and wine from three sources. From each source, one wine and four juice samples (a control and three treatments) were prepared. The following three treatments were applied to the crushed grapes prior to pressing the juice: freezing and thawing; skin contact with 250 ppm Pectinol VR (a pectinase); and skin contact with 250 ppm Rohapect D5L (another pectinase). The trained panel developed descriptive terminology which differed between Pinot noir juice and Pinot noir wine. The juice treatments created subtle, if any, aroma differences. Treatment differences were evident in color, as measured by human perception and by instrumental measurement. Few characteristics of wine aroma and/or color correlated with juice aroma and/or color. Perceived color correlated well with Somer's color density measurement (the sum of the corrected absorbances at 420 and 520 nm.). Some of the same samples were evaluated by a wine industry panel. They appeared to disagree regarding the definition of varietal character. Further research utilizing grapes from many sources is necessary to determine whether Pinot noir wine quality can be predicted from Pinot noir juice quality. / Graduation date: 1987

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.

The determination of wine authenticity and the detection of adulteration are attracting an increasing amount of attention for wine producers, researchers and consumers. Wine authentication and classification based on geographical origin has been widely studied. Most of these studies have achieved successful classification results. However, these studies have involved complicated and expensive procedures. Visible and near infrared spectroscopy (Vis-NIR) is recognized as a rapid and non-destructive technique. In recent years, several studies have been conducted using Vis-NIR spectroscopy to analyze wine for both quantitative and qualitative purposes. The aim of this research was to investigate the geographical classification of wines using Vis-NIR spectroscopy. The effect of temperature and measurement mode (transmission and transflectance) on Vis-NIR spectra was investigated to identify optimal conditions for wine sample analysis. It was found the optimal temperature is between 30 to 35°C and the shorter pathlength measurement condition has better prediction ability. Classification by geographical origin using Vis-NIR spectroscopy was investigated for sixty-three Tempranillo wines from Spain and Australia, and fifty Riesling wines from Australia, New Zealand and Europe. Discriminant partial least square regression (DPLS) and linear discriminant analysis (LDA) based on PCA scores were used to perform classification. Over 90% of the Tempranillo wines were correctly classified according to their geographical region using both DPLS and LDA. A classification rate of 72% was achieved for the Riesling wines. Vis-NIR technique provides a similar degree of reliability on wine classification comparable to those obtained using chemical composition. The results of this study demonstrate potential for Vis-NIR spectroscopy combined with multivariate analysis as a rapid method for classifying wines by geographical origin. / Thesis (M.Eng.Sc.)--School of Chemical Engineering, 2006.

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

Thesis (MBusiness-Research)--University of South Australia, 2001.

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