Multinuclear N M R spectroscopy and conductivity measurements showed that the 1 -ethyl-3-methylimidazolium cation, [emim] +, not only forms strong hydrogen bonds (using all three ring protons H2, H4 and H5) with halide ions in polar molecular solvents (e.g. ethanenitrile) and ionic liquids, but that it exists in a quasi-molecular state, [emim]X, in non-polar solvents (e.g. trichloro-and dichloromethane), showing a conventional aromatic stacking phenomenon.Over the past ten years the perception of the ability of the 1ethyl-3-methylimidazolium cation, [emim] + , 1,2 to enter into hydrogen bonds with halide ions has developed from not p ~s s i b l e , ~ through contr~versial,~ to widely a ~c e p t e d . ~. ~ However, the strongest evidence for these claims has always rested upon solid-state X-ray crystallographic determinations of the structures of both [emim]+ 4,7 and [edmim]+ (edmim = 1ethyl-2,3-dimethylimidazolium) salts.* A number of first-class solution studies have been reported, 5*6*9 yet no incontrovertible evidence has yet been presented that the [emim]' cation is capable of forming hydrogen bonds in solution. Proton NMR spectra of room-temperature [emim]C1-A1C13 ionic liquids are known to be very composition dependent, particularly in the basicIn particular, the H2 proton is very sensitive, moving significantly upfield with increasing acidity. This has been widely interpreted in terms of a stacked oligomeric model 3,5 in which anions and cations alternate, the anions being associated with the imidazolium ring both directly above and below its plane. Nevertheless, a 'H NMR study l 1 of several imidazole and imidazolium derivatives in CD,Cl, has shown that the chemical shift of the H2 proton was sensitive to the nature of the anion present, and hydrogen bonding between discrete ion pairs was postulated to explain this result. We thus decided to undertake a definitive study of the NMR characteristics of [emim]X (X = CI, Br or I) in molecular solvents, free of the aporia associated with ionic liquids. We demonstrate here, using principally the techniques of multinuclear NMR spectroscopy and conductivity measurements, that [emim] + not only forms strong hydrogen bonds (using all three ring protons H2, H4 and H5) with halide ions in polar molecular solvents (e.g. ethanenitrile, MeCN) and ionic liquids, but that it exists in a quasi-molecular state, [emim]X, in non-polar solvents (e.g. CHCl, and CH,Cl,), showing a conventional aromatic stacking phenomenon. Experiment a1N M R Studies.-Deuterium oxide (99%) was distilled in O ~U O before use; CD3CN and CD2C12 were distilled from calcium hydride under dry dinitrogen. Samples of [emim]X (X = C1, Br

Background and Aims Oxygen (O2) plays a fundamental role in the establishment of wine style and aroma. The effect of O2 treatment during fermentation on the formation of volatile sulfur compounds (VSCs) and the subsequent impact on the sensory profile of wine was investigated. Traditional VSC remediation strategies were also evaluated. Methods and Results Shiraz wines were treated with O2 at several levels during fermentation by sparging rotary fermenters with three types of gas mixtures (40% O2, 21% O2 and N2). The controls were not sparged with any gas and were subsequently subjected to three remedial treatments (aerative racking, early‐ and late‐Cu2+ addition). Wines were analysed for VSCs, fermentation products, concentration of residual metals, as well as their sensory profile. Non‐oxygenated ferments and wines contained a higher concentration of VSCs and a lower concentration of fermentation products and differences in the concentration of metals. Volatile sulfur compounds responsive to O2 treatment were identified and a relationship between O2 dose and concentration on VSC formation was demonstrated. The ‘early‐Cu2+ addition’ remediation strategy proved the most effective in reducing the impact of ‘reductive’ aromas in non‐oxygenated wines. Conclusions The risk of producing a wine with high VSC concentration that negatively impacts wine aroma as well as with a low concentration of fermentation products associated with positive red fruit aromas was decreased by treating wines with O2 during fermentation. Significance of the Study This work specifically examines important aspects of O2 treatment during fermentation in relation to ‘reductive’ aroma characters and the overall impact on the wine's sensory attributes.

To remain competitive in increasingly overcrowded markets, yeast strain development programmes are crucial for fermentation-based food and beverage industries. In a winemaking context, there are many yeast phenotypes that stand to be improved. For example, winemakers endeavouring to produce sweet dessert wines wrestle with fermentation challenges particular to fermenting high-sugar juices, which can lead to elevated volatile acidity levels and extended fermentation times. In the current study, we used natural yeast breeding techniques to generate Saccharomyces spp. interspecific hybrids as a non-genetically modified (GM) strategy to introduce targeted improvements in important, wine-relevant traits. The hybrids were generated by mating a robust wine strain of Saccharomyces cerevisiae with a wine isolate of Saccharomyces bayanus, a species previously reported to produce wines with low concentrations of acetic acid. Two hybrids generated from the cross showed robust fermentation properties in high-sugar grape juice and produced botrytised Riesling wines with much lower concentrations of acetic acid relative to the industrial wine yeast parent. The hybrids also displayed suitability for icewine production when bench-marked against an industry standard icewine yeast, by delivering icewines with lower levels of acetic acid. Additionally, the hybrid yeast produced wines with novel aroma and flavour profiles and established that choice of yeast strain impacts on wine colour. These new hybrid yeasts display the desired targeted fermentation phenotypes from both parents, robust fermentation in high-sugar juice and the production of wines with low volatile acidity, thus establishing their suitability for wine styles that are traditionally troubled by excessive volatile acidity levels.

The juice used to make white wine can be extracted using various physical processes that affect the amount and timing of contact of juice with skins. The influence of juice extraction processes on the mouthfeel and taste of white wine and their relationship to wine composition were determined. The amount and type of interaction of juice with skins affected both wine total phenolic concentration and phenolic composition. Wine pH strongly influenced perceived viscosity, astringency/drying, and acidity. Despite a 5-fold variation in total phenolics among wines, differences in bitter taste were small. Perceived viscosity was associated with higher phenolics but was not associated with either glycerol or polysaccharide concentration. Bitterness may be reduced by using juice extraction and handling processes that minimize phenolic concentration, but lowering phenolic concentration may also result in wines of lower perceived viscosity.

Stable isotope analysis of grape juices and fermented products involving 2H-NMR spectroscopy and isotope ratio mass spectroscopy was carried out in combination with elemental determinations performed by atomic absorption spectroscopy using flame and thermal ionisation. One hundred and sixty five grape samples were carefully collected in well-defined vineyards of France situated in Alsace, Burgundy, Beaujolais and the Loire Valley. Moreover, the samples from Burgundy were picked from four typical Appellations (CBtes de Nuits, CBtes de Beaune, CBtes Chalonnaises and Mficonnais) in order to 'zoom' the approach to smaller production areas. An exhaustive statistical evaluation of the 165 x 16 data set was carried out by analysis of variance and principal component analysis. To conclude this study, the classification of the samples in typical Appellations was carried out by discriminant analysis with a nearly 100% degree of achievement.

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It is generally acknowledged that oxygen can have both a positive and a negative impact on a wine's chemical composition and sensory attributes. During the production process, from the initial harvesting of grapes to maturation in bottle, there are numerous points at which oxygen can be introduced, either inadvertently or intentionally. The impact of oxygen on fermentative performance, as well as during maturation, has been the subject of extensive research, both during winery operations and in the final package. Recent studies have highlighted the impact of oxygen on wine chemistry during early parts of the winemaking process. This review will discuss the effect of oxygen introduction at various points, from harvest to completion of fermentation, of wine chemical composition. In reviewing the opportunities to modulate wine chemistry and stylistic outcomes through the control of oxygen exposure, the review will highlight critical knowledge gaps in the underlying science behind some processes that are common within the wine industry.

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