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Proanthocyanidins (PAs) were isolated from the skins, seeds and flesh of commercially ripe grapes, and from wine and marc produced from the same source. In the grape berry, skin PAs accounted for 54% of the total extractable PA, while seed and flesh-derived PA accounted for 30% and 15% of the total, respectively. Following fermentation, 25% of the fruit PA was found in the wine, while 27% was found in the pericarp isolated from marc, and 48% was unaccounted for (either remaining in the seed or adsorbed to lees). To investigate the role that cell wall material (CWM) has on PA extraction during fermentation, CWM isolated from skin and flesh were combined with PA in model suspensions. In general, the affinity of flesh CWM for PA increased with increasing PA molecular mass (MM); however, this relationship was not observed for the interaction of skin CWM with skin PA. Subsequent experiments suggest that the differences in the interaction of flesh and skin CWM with PA of higher MM (>15000 g/mol) may be limited by the structure of the CWM. Observed variations in the composition between skin and flesh CWM may explain the differences in PA interaction at high MM. Among wine-derived PA, no higher MM material was detected, suggesting that, during vinification, higher MM PA are nonextractable and/or are removed from the wine by interaction with CWM.

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The key aroma compounds of premium Australian Shiraz wines from the warm Barossa Valley and cooler Margaret River regions were characterized. GC-Olfactometry was conducted to determine the most important volatile compounds, which were then quantitated. The wine from the Barossa Valley had higher concentrations of ethyl propanoate, dimethyl sulfide (DMS), and oak-derived compounds, whereas the Margaret River wine contained above threshold concentrations of the 'cheesy' compounds 2- and 3-methylbutanoic acid, as well as rotundone, the 'pepper'-smelling compound. The aromas were reconstituted by combining 44 aroma compounds, and sensory descriptive analysis was used to investigate the importance of the omission of several compounds, including DMS, rotundone, fatty acids, and β-damascenone, and the influence of nonvolatiles was also assessed. The study showed that the aroma of the Shiraz wines could be reconstituted in both cases, with the changes in the nonvolatile fraction having a large influence.

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Different molecular structures of grape tannins have been shown to influence astringency, however, the in-mouth sensory effects of different molecular structures in red wine tannins remains to be established. The objective of this research was to assess the impact of wine tannin structure on in-mouth sensory properties. Wine tannin was isolated from Cabernet Sauvignon wines of two vintages (3 and 7 years old) and separated into two structurally distinct subfractions with liquid-liquid fractionation using butanol and water. The aqueous subfractions had greater mean degree of polymerization (mDp) and contained a higher proportion of epigallocatechin subunits than the butanol-soluble subfractions, while the older wine tannin fractions showed fewer epicatechin gallate subunits than the younger tannin fractions. The red wine had approximately 3:1 mass ratio of the aqueous and butanol tannin subfractions which approximated an equimolar ratio of tannin in each subfraction. Descriptive sensory analysis of the tannin subfractions in model wine at equimolar concentrations revealed that the larger, more water-soluble wine tannin subfractions from both wines were perceived as more astringent than the smaller, more hydrophobic and more highly pigmented butanol-soluble subfractions, which were perceived as hotter and more bitter. Partial least squares analysis indicated that the greater hydrophobicity and color incorporation in the butanol fractions was negatively associated with astringency, and these characteristics are also associated with aged wine tannins. As the larger, water-soluble tannins had a greater impact on the overall wine astringency, winemaking processes that modulate concentrations of these are likely to most significantly influence astringency.

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.

Background and Aims:  Commercial winemakers observed differences in wine sensory properties among wines produced from vines of three different pruning treatments in a single vineyard. To clarify the relationships between berries and wine quality, this study examined berry size and berry composition and the quality rating for wines produced from the pruning treatments. Methods and Results:  The study was conducted over three seasons. Berries from Machine‐, Cane‐ and Spur‐pruned vines were sampled at commercial harvest for analysis of berry size and berry phenolic composition. Wines made from each treatment were assessed for quality by a panel of winemakers. Machine berries were lighter and had higher concentrations of anthocyanins, tannins and total phenolics than Cane or Spur. Machine wines had the lowest quality scores. Comparing vintages, berries from 2004 were lighter, but did not always differ in phenolic composition to other vintages, and wines from 2004 had lower quality scores than the other vintages. Vintage effects were generally stronger than pruning effects. Conclusions:  In this study, high berry anthocyanins, total phenolics and tannin concentration measures were not good indicators of wine quality scores. Changes in vineyard treatments and, in particular, vintage influences, produce incremental, but potentially important, changes to berry size and composition and to wine quality. Significance of the Study:  This study is unique in its focus on the commercial reality of producing wines to a specific style and quality, while bringing scientific rigour to investigating the relationships between berries and wine quality in this vineyard over a number of vintages.