Protein-induced wine haze is a major concern to the wine industry worldwide. While the presence of protein haze is unlikely to affect the sensory profile, consumers will generally reject wines containing hazes as they appear microbially spoiled. Consequently, an important step during commercial winemaking is to treat wines with bentonite, which removes heat unstable proteins by adsorption, and prevents haze formation. Whilst this process is effective, it is claimed to adversely affect the quality of the treated wine under certain conditions. Furthermore, 5-10% of the wine volume is typically occluded in bentonite lees. This wine is either lost or substantially diminished in quality and value during recovery. Therefore the development of alternative and economically viable process technologies that maintain wine quality and reduce costs would be highly desirable. This thesis is concerned with the development of alternative and innovative approaches to bentonite treatment of wine. Particular emphasis was placed on developing practical research outcomes that could be readily commercially adopted. Pursuant to this, fundamental research regarding the mechanics of protein adsorption onto bentonite was undertaken to gain an understanding of how bentonite properties relate to adsorption and settling behaviour in wine. The effect of bentonite heat treatment on protein adsorption performance and settling behaviour in a model wine was also investigated. In general, heating was found to increase the initial hindered settling velocity and reduce both protein adsorption capacity and the final volume of lees. Particle size, pH and cation exchangeability of bentonites and the changes that occur to these properties on heating are related to the nature of bonding between cations and the clay surface, as are protein adsorption performance and settling behaviour. Partial Least Squares (PLS) Analysis showed that the variance in individual cation exchangeability and the total cation exchange capacity was primarily responsible for the observed variance in protein adsorption performance and settling behaviour. PLS analysis was also used to develop correlations for the prediction of adsorption and settling behaviour, based on the physical and chemical properties of the bentonites tested. Qualitative comparison of the volume fraction of model wine occluded by each of the bentonites indicated that certain heat treatments may result in a combination of protein adsorption performance and settling behaviour which would produce a significant reduction in wine loss. The effect of different factors on adsorption of a purified grape protein (VVTL1) in a model wine was investigated using a factorial design approach with surface response analysis. Adsorption of VVTL1 by sodium bentonite was well characterised by the Langmuir adsorption isotherm. pH, temperature, potassium concentration ([K]), and the pH*[K]interaction were all found to have a significant effect (p < 0.05) on the adsorption capacity. Block effects appeared to correctly correlate with bentonite slurry age, suggesting that increasing slurry age may have a positive effect on adsorption capacity. Ethanol concentration, phenolic (caffeic acid and catechin) oncentration, sugar (glucose and fructose) concentration, as well as the pH*temperature and temperature*[K] interactions did not have a significant effect. The equilibrium constant was found to be independent of the factors studied. This may be explained by changes in protein structure and charge with pH, which affect electrostatic interaction with the bentonite surface. Variation in potassium concentration can cause similar effects and may also influence adsorption capacity by affecting bentonite swelling and zeta potential. This knowledge was applied to the development of in-line dosing of bentonite as an alternative process strategy for commercial use. Field tests of in-line dosing at a commercial winery were conducted on a Sultana wine and Gordo (Muscat of Alexandria) juice with Vitiben and SIHA-Aktiv-Bentonit G bentonites. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration were reduced in a similar manner upon fining. These reductions were achieved with a contact time of less than two minutes. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests did not detect any difference between untreated, in-line dosed and batch fined wine. A dynamic simulation model of in-line dosing was developed and compared with field trial results, marking the first quantitative study of the dynamic adsorption kinetics of wine protein adsorption onto bentonite. The simulation results confirmed the rapid adsorption behaviour observed during field testing, and provided strong evidence that protein adsorption occurs predominantly on the external particle surface only, with adsorption kinetics being limited by external-film mass transfer. Incomplete separation of bentonite from wine/juice during centrifugation produced a carryover of up to 30% of the added bentonite into the clarified wine. If this problem can be overcome, use of in-line dosing instead of batch fining could eliminate significant value losses presently arising from quality downgrades of wine recovered from bentonite lees by rotary drum vacuum filtration. Moreover, in-line dosing of selected heattreated bentonites under optimal wine or juice conditions may provide even further costs savings whilst maintaining wine quality. / Thesis (Ph.D.)-- University of Adelaide, School of Chemical Engineering, 2006.

Protein-induced wine haze is a major concern to the wine industry worldwide. While the presence of protein haze is unlikely to affect the sensory profile, consumers will generally reject wines containing hazes as they appear microbially spoiled. Consequently, an important step during commercial winemaking is to treat wines with bentonite, which removes heat unstable proteins by adsorption, and prevents haze formation. Whilst this process is effective, it is claimed to adversely affect the quality of the treated wine under certain conditions. Furthermore, 5-10% of the wine volume is typically occluded in bentonite lees. This wine is either lost or substantially diminished in quality and value during recovery. Therefore the development of alternative and economically viable process technologies that maintain wine quality and reduce costs would be highly desirable. This thesis is concerned with the development of alternative and innovative approaches to bentonite treatment of wine. Particular emphasis was placed on developing practical research outcomes that could be readily commercially adopted. Pursuant to this, fundamental research regarding the mechanics of protein adsorption onto bentonite was undertaken to gain an understanding of how bentonite properties relate to adsorption and settling behaviour in wine. The effect of bentonite heat treatment on protein adsorption performance and settling behaviour in a model wine was also investigated. In general, heating was found to increase the initial hindered settling velocity and reduce both protein adsorption capacity and the final volume of lees. Particle size, pH and cation exchangeability of bentonites and the changes that occur to these properties on heating are related to the nature of bonding between cations and the clay surface, as are protein adsorption performance and settling behaviour. Partial Least Squares (PLS) Analysis showed that the variance in individual cation exchangeability and the total cation exchange capacity was primarily responsible for the observed variance in protein adsorption performance and settling behaviour. PLS analysis was also used to develop correlations for the prediction of adsorption and settling behaviour, based on the physical and chemical properties of the bentonites tested. Qualitative comparison of the volume fraction of model wine occluded by each of the bentonites indicated that certain heat treatments may result in a combination of protein adsorption performance and settling behaviour which would produce a significant reduction in wine loss. The effect of different factors on adsorption of a purified grape protein (VVTL1) in a model wine was investigated using a factorial design approach with surface response analysis. Adsorption of VVTL1 by sodium bentonite was well characterised by the Langmuir adsorption isotherm. pH, temperature, potassium concentration ([K]), and the pH*[K]interaction were all found to have a significant effect (p < 0.05) on the adsorption capacity. Block effects appeared to correctly correlate with bentonite slurry age, suggesting that increasing slurry age may have a positive effect on adsorption capacity. Ethanol concentration, phenolic (caffeic acid and catechin) oncentration, sugar (glucose and fructose) concentration, as well as the pH*temperature and temperature*[K] interactions did not have a significant effect. The equilibrium constant was found to be independent of the factors studied. This may be explained by changes in protein structure and charge with pH, which affect electrostatic interaction with the bentonite surface. Variation in potassium concentration can cause similar effects and may also influence adsorption capacity by affecting bentonite swelling and zeta potential. This knowledge was applied to the development of in-line dosing of bentonite as an alternative process strategy for commercial use. Field tests of in-line dosing at a commercial winery were conducted on a Sultana wine and Gordo (Muscat of Alexandria) juice with Vitiben and SIHA-Aktiv-Bentonit G bentonites. Fining performance was monitored by heat testing and quantification of heat unstable protein by HPLC. Heat test turbidity and heat unstable protein concentration were reduced in a similar manner upon fining. These reductions were achieved with a contact time of less than two minutes. Sensory evaluation of Sultana wine fined with Vitiben by balanced reference duo-trio difference tests did not detect any difference between untreated, in-line dosed and batch fined wine. A dynamic simulation model of in-line dosing was developed and compared with field trial results, marking the first quantitative study of the dynamic adsorption kinetics of wine protein adsorption onto bentonite. The simulation results confirmed the rapid adsorption behaviour observed during field testing, and provided strong evidence that protein adsorption occurs predominantly on the external particle surface only, with adsorption kinetics being limited by external-film mass transfer. Incomplete separation of bentonite from wine/juice during centrifugation produced a carryover of up to 30% of the added bentonite into the clarified wine. If this problem can be overcome, use of in-line dosing instead of batch fining could eliminate significant value losses presently arising from quality downgrades of wine recovered from bentonite lees by rotary drum vacuum filtration. Moreover, in-line dosing of selected heattreated bentonites under optimal wine or juice conditions may provide even further costs savings whilst maintaining wine quality. / Thesis (Ph.D.)-- University of Adelaide, School of Chemical Engineering, 2006.

Dans l’optique de comprendre et maitriser le vieillissement des vins, en particulier des vins blancs, il est nécessaire d’approfondir nos connaissances sur les mécanismes physico-chimiques d’oxydation liés aux processus d’oxygénation. Pour cela, il est important d’avoir des outils permettant la quantification de la capacité antioxydante des vins blancs, et l’identification des composés impliqués dans celle-ci, afin de pouvoir anticiper l’aptitude au vieillissement d’un vin.Lors de cette étude, des analyses de la capacité antioxydante par DPPH et Résonnance Paramagnétique Electronique (RPE) ont été réalisées sur un grand nombre de vins en cours d’élevage et issus de plusieurs millésimes. En parallèle des analyses métabolomiques, principalement par Chromatographie Liquide couplée à la Spectrométrie de Masse (UPLC-Q-TOF-MS) mais également par Spectrométrie de Masse à Résonance Cyclotronique des Ions et à Transformée de Fourier (FT-ICR-MS) ont été réalisées.L’optimisation de la méthode DPPH, pour l’analyse des vins blancs a révélé une réactivité importante des composés soufrés, avec des capacités antioxydantes similaires à celles des composés phénoliques. La comparaison de cette méthode optimisée à la méthode de référence du laboratoire (RPE) sur plus de 106 vins, a montré la complémentarité de l’information apportée par ces deux différentes méthodes de mesure de capacité antioxydante. Le traitement statistique des corrélations avec les analyses métabolomiques réalisées sur 287 vins a permis de révéler une liste de 380 marqueurs moléculaires associés à la capacité antioxydante des vins. Une méthode alternative de mesure du potentiel antioxydant des vins blancs a également été développée, qui repose sur l’identification de composés nucléophiles naturellement présents et susceptibles de piéger les quinones formées au cours de mécanismes d’oxydation. Outre des composés soufrés, nous avons montré que différents peptides ayant des propriétés antioxydantes présentent de telles propriétés nucléophiles. Dans un second temps, l’étude de différentes pratiques œnologiques (élevage, hyperoxygénation ou sulfitage) a permis de déterminer leurs impacts sur la capacité antioxydante des vins mais également sur les marqueurs moléculaires associés. Il apparait ainsi une augmentation significative de la capacité antioxydante des vins au cours de l’élevage. De plus, cette augmentation de la capacité antioxydante est associée à une consommation de peptides en début d’élevage, ainsi qu’à l’apparition de nouveaux composés dans les vins et ce indépendamment du millésime. Les composés qui apparaissent semblent être majoritairement des composés phénoliques provenant potentiellement du bois ou de l’autolyse des levures. Les vins issus de moûts protégés par l’ajout précoce de sulfites ont une capacité antioxydante plus élevée par rapport aux vins issus de moûts hyperoxygénés. De plus, la protection du moût à un impact important sur la composante moléculaire soufrée retrouvée dans les vins. Ainsi, il a été observé une quantité beaucoup plus faible de composés soufrés (peptides ou non) dans les vins issus de moûts hyperoxygénés montrant donc une consommation de ces composés dans les mécanismes d’oxydation du vin. En résumé, ces résultats révèlent pour la première fois l’importance des composés soufrés dans les mécanismes de protection des vins blancs de Bourgogne vis-à-vis de l’oxydation, par leur capacité de piégeur de radicaux mais également de piégeur de quinones. / In order to understand and control the aging of wines, particularly white wines, it is necessary to deepen our knowledge about the physico-chemical mechanisms of oxidation related to oxygenation processes. For this, it is important to have tools to quantify the antioxidant capacity of white wines, and to identify the compoiunds involved, in order to anticipate the aging ability of a wine.In this study, analyzes of the antioxidant capacity by DPPH and Electron Paramagnetic Resonance (EPR) were carried out on a large number of wines during aging and from several vintages, in parallel with metabolomic analyzes, mainly carried out by Liquid Chromatography Coupled to Mass Spectrometry (UPLC-Q-TOF-MS) but also by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS).Optimization of the DPPH method for the analysis of white wines, showed a high reactivity of sulfur compounds with similar antioxidant capacities to those of phenolic compounds. The comparison of this optimized method with the laboratory reference method (EPR) on more than 106 wines, showed the complementarity of the information provided by these two different methods of measuring an antioxidant capacity.Combining antioxidant capacity measurements and metabolomic analyzes, it was possible to determine a list of molecular markers related to the antioxidant capacity of white wines. During this study, a focus on nucleophilic compounds present in wines has also been realized, these compounds being able to react with the quinones formed during oxidation and thus to play a role in the oxidation mechanisms of white wines. Besides sulfur compounds, we showed that several peptides with antioxidant properties could exhibit such nucleophilic behavior. In a second step, the study of different oenological practices (aging, hyperoxygenation or adding SO2 to must) allowed to determine their impacts on the antioxidant capacity of wines but also on the associated molecular markers. It thus appears a significant increase in the antioxidant capacity of the wines during aging. In addition, this increase in antioxidant capacity is associated with a consumption of peptides at the beginning of aging, but also with the appearance of compounds in wines, regardless of the vintage. The compounds that appear are potentially phenolic compounds which can come from wood or lees autolysis. Wines from protected musts with sulfites addition, have a higher antioxidant capacity compared to wines from hyperoxygenated musts. In addition, the protection of musts has a significant impact on the sulfur component found in wines. Thus, a much smaller amount of sulfur compounds (peptides or not) has been observed in wines derived from hyperoxygenated musts, showing a consumption of these compounds in the oxidation mechanisms. Overall, these results reveal for the first time the importance of sulfur compounds in the mechanisms of protection of white wines from Burgundy against oxidation, by radical scavenging capacity and quinone trapping.

Thesis (MSc)--Stellenbosch University, 2011 / ENGLISH ABSTRACT: South African Chenin blanc wine is characterised by its style diversity and has been receiving more industry limelight over the past few years. Three dry Chenin blanc wine styles are currently described by the wine industry as Fresh and Fruity (FF), Rich and Ripe unwooded (RR-unwooded) and, Rich and Ripe wooded (RR-wooded). According to the South African wine industry, however, consumers seem to be somewhat confused by these various Chenin blanc wine styles, which have not yet been clearly defined and classified. During this study we investigated the following perspectives of this wine style classification confusion: Currently, no specified sensory method is being used to differentiate between wine styles of a single wine cultivar, such as Chenin blanc. The sorting method can be used as a more cost and time effective classification and profiling method than general quantitative descriptive analysis (QDA). It was therefore investigated whether both uninstructed and instructed sorting, with consumers and wine experts, can be used to classify and describe the Chenin blanc wine styles similarly to QDA. The increase in young wine consumers, Generation Y, introduces new wine marketing opportunities for the wine industry which need to be investigated. Young consumers are not aware of the various Chenin blanc wine styles, which may influence their wine preferences. The influence of wine style knowledge on these consumers’ wine style preferences were investigated during blind and wine style informed preference test. Any segmentation within this Generation Y group was also investigated with regards to their Chenin blanc wine style preferences and/or exploratory data. The following scientific and industrial findings were made: QDA was successfully substituted by instructed and uninstructed sorting tasks. Although the sorting tasks easily differentiated between wooded and unwooded wines, QDA differentiated more successfully between the unwooded wines. Wine tasting experience did not significantly influence the sorting results of the consumers versus the wine experts, but more experienced panellists consistently used fewer descriptors than untrained consumers. All panellists sorted products slightly better when they were provided with wine style sorting instructions. However, there were no significant differences between the instructed and uninstructed sorting task results, i.e. a wine style descriptor list did not improve panellists’ abilities to describe their sorted wine groups. South African Chenin blanc wines can definitely be divided into wooded and unwooded wine styles, i.e. two wine style groups, but the unwooded Chenin blanc wine spectrum formed a wine-style-continuum. This finding is apparent from both the sorting and QDA methods. The unwooded continuum wines can further be differentiated from one another with the use of a fresh-to-mature scale and/or a light-to-full body scale during QDA. Generation Y wine consumers preferred all the Chenin blanc wine styles equally and moderately during the blind tasting, but their knowledge of the wine style concepts significantly increased their preferences for the wines during the informed wine style tasting. The cognitive influence of wine style knowledge is therefore powerful in terms of influencing a consumer’s wine preferences. Other interesting correlations were also made between Generation Y consumers’ wine style preferences and their exploratory data. / AFRIKAANSE OPSOMMING: Suid-Afrikaanse Chenin blanc wyn word gekarakteriseer deur styl diversiteit en is die afgelope paar jaar meer in die kollig. Drie droë Chenin blanc wynstyle word tans deur die wynbedryf beskryf as: Vars en Vrugtig, Ryk en Ryp ongehout en, Ryk en Ryp gehout. Volgens die Suid- Afrikaanse wynbedryf is daar heelwat verwarring is tussen hierdie Chenin blanc wynstyle weens die feit dat hierdie wynstyle nog nie duidelik gedefinieer en geklassifiseer is nie. Tydens die huidige studie het ons die volgende perspektiewe van hierdie wynstyl-verwarring ondersoek: Huidiglik word daar geen gespesifiseerde sensoriese metode gebruik om te onderskei tussen verskillende wynstyle van ’n enkele wyn kultivar, soos Chenin blanc, nie. Die sorteringsmetode kan gebruik word, instede van kwantitatiewe beskrywende analise, as ’n meer koste- en tyd-effektiewe produk klassifikasie en profileringsmetode. DIt was dus ondersoek of beide geïnstrukteerde en ongeïnstrukteerde sorteringstake, met verbruikers en wynkundiges, gebruik kan word om die verskeie Chenin blanc wynstyle kan profileer en klassifiseer soortgelyk soos kwantitatiewe beskrywende analise. Die toename in jong verbruikers, Generasie Y, skep nuwe wynbemarkingsgeleenthede wat ondersoek moet word. Jong verbruikers se onbewustheid van die verskeidenheid Chenin blanc wynstyle mag hulle voorkeure vir hierdie wyne beïnvloed. Die invloed van wynstyl kennis op hierdie jong verbruikers se wynstyl voorkeure was ook ondersoek gedurende ’n blinde en ’n wynstyl-ingeligte voorkeur toets. Enige segmentasie binne hierdie Generasie Y verbruikersgroep was ook ondersoek in verband met hul Chenin blanc wynstyl voorkeure en/of verkennende data. Die volgende wetenskaplike en industriële bevindings is gemaak: Kwantitatiewe beskrywende analise kan suksesvol vervang word deur beide geïnstrukteerde en ongeïnstrukteerde sorteringsmetodes. Alhoewel die sorteringsmetodes maklik gebruik kon word om te onderskei tussen gehoute en ongehoute wyne, kan kwantitatiewe beskrywende analise fyner onderskeid tref tussen die individuele ongehoute wyne. Die wynproe-ervaringsvlak het geen invloed op die sorteringsresultate gehad nie, maar meer ervare paneellede het konsekwent gebruik gemaak van minder beskrywende terme as onopgeleide verbruikers wat baie meer en verskillende soorte terme gebruik het. Beide panele het effens beter gesorteer wanneer hulle spesifieke wynstyl sorteringsinstruksies ontvang het. Daar was egter geen beduidende verskille tussen die geïnstrukteerde en ongeïnstrukteerde sorteringsresultate nie, wat daarop dui dat sorteringsinstruksies en ’n lys van wynstyl beskrywings nie die paneellede se wyse van sortering verander het nie. Suid-Afrikaanse Chenin blanc wyne kan definitief verdeel word in gehoute en ongehoute wynstyle, d.w.s twee wynstyl groepe, maar die ongehoute Chenin blanc wyn spektrum vorm ’n wynstyl-kontinuum. Laasgenoemde is bevind tydens beide die sorteringstake asook kwantitatiewe beskrywende analise. Die ongehoute kontinuum wyne kan verder van mekaar onderskei word met behulp van ‘n vars-tot-volryp en/of ‘n ligte-tot-volmond skaal tydens kwantitatiewe beskrywende analise. Alle jong wyn verbruikers het ewe veel van al die wynstyle gehou tydens die blinde wynstyl voorkeur toets, maar tydens die wynstyl-ingeligte voorkeur toets het hulle voorkeure vir al die wynstyle drasties verbeter. Die kognitiewe invloed van Chenin blanc wynstyl kennis kan dus lei tot hoër voorkeure vir die wynstyle. Ander interessante korrelasies is ook bevind tussen hierdie Generasie Y wyn verbruikersgroep se wynstyl voorkeure en hul verkennende data.

Tout au long du procédé d’élaboration d’un vin, des réactions d’oxydation peuvent se produire y compris au cours du vieillissement en bouteilles. Depuis quelques années, la profession viti-vinicole est confrontée au problème de l’oxydation prématurée des vins blancs.. A ce jour, peu d’études ont pu apporter des explications d’ordre chimique à ce phénomène, et les mécanismes réactionnels intervenant restent peu connus.L’objectif de ce travail de thèse est d’apporter, au travers d’une analyse moléculaire non ciblée en spectrométrie de masse à transformée de Fourier et à résonance cyclotronique des ions (FT-ICR-MS) couplée à une étude chimiométrique, des réponses originales aux questions posées par la problématique actuelle d’oxydation prématurée des vins blancs. Nous avons montré suite à l’étude d’une série de vins oxydés prématurément non seulement la grande diversité chimique des vins, mais aussi la présence d’un ensemble de masses typiques associées à ce phénomène. Pour une meilleure compréhension de l’origine de cette problématique, nous avons considéré deux autres types d’oxydation : une oxydation relative exclusivement à un apport contrôlé en oxygène et une autre relative à l'évolution naturelle de vins en bouteilles. Cette dernière consiste en le suivi de l'évolution des espaces chimiques de séries verticales de vins blancs et rouges en fonction du temps. Sur la série verticale des vins blancs allant de 1979 à 2006, une charnière à l’année 1990 a été observée avec des groupes de masses typiques de chacun des vins jeunes (1979-1990) et des vieux vins (1991-2006).La comparaison entre les espaces chimiques discriminants chacun de ces trois types d’oxydation ne révèle la présence que de trois masses en commun, ce qui appuie l'hypothèse de causes multiparamétriques à l’oxydation prématurée des vins blancs, qui ne serait donc pas un phénomène du exclusivement à une exposition non contrôlée à l'oxygène.Des essais d’élucidation structurale en FT-ICR-MS/MS des masses discriminantes des vins oxydés et de la série verticale ont été effectués et des schémas de fragmentation pour certaines masses sont proposés / During winemaking processes, many oxidation reactions may occur especially during the aging period. Recently, white wines are characterized by a problem of premature oxidation for which few studies have provided chemical explanation. To date, the involved mechanisms in this phenomenon remain poorly understood.The aim of this thesis project is to provide, through an untargeted molecular analysis using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) coupled to chemometric analysis, original clue to understand the premature oxidation of white wines. Based on the study of a series of premature oxidized white wines, we were able to elucidate the high complexity and the chemical diversity of wine, and got out typical masses characterizing the oxidation state. In order to better understand the origin of this phenomenon, we considered two alternative possibilities of oxidation: the first one induced by oxygen, and the second through a natural evolution of wines in bottles. The latter included the monitoring of the chemical evolution of white and red wines as a function of time. A very interesting result was obtained on the vertical series of white wines from 1979 to 2006, where two groups were separated at the 1990 vintage to provide a group of old wines (1979-1990) and a group of new wines (1991-2006). Typical discriminant masses were found for each group.A comparison between the chemical spaces discriminating each of the three types of oxidation (premature oxidation, oxidation with oxygen and natural evolution of wine in bottle) revealed very few common masses that may indicate that the phenomenon of premature oxidation is indeed influenced by multiple factors.Finally, a structural elucidation of the typical masses of the groups of oxidized and aged wines were established using FT-ICR-MS/MS. Possible fragmentations schemes of some of these masses were proposed