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Background and Aims: Aeration during fermentation of red wines has the potential to enhance positive red fruit attributes and suppress less desirable reductive characteristics. The implementation of aeration in commercial winemaking, however, is impeded by the lack of a clear understanding of both the major benefits of its use and the nature of the aeration regimes required to modify the finished product. This work aimed to evaluate the impact of different modes of aeration, varying in their timing, duration and intensity, on fermentation duration, chemical composition and sensory properties of Shiraz wine. Methods and Results: Forty‐eight pilot‐scale fermentations (450 kg) were treated with different aeration modalities and compared to non‐aerated fermentations across four vintages. This work demonstrated the reproducible effects of aeration, resulting in an enhancement of fruit‐related attributes, decreases in colour intensity and a lowering of astringent mouthfeel and bitterness. The development of attributes describing possible oxidation or undesirable volatility were not observed in this work. These effects on wine sensory attributes were correlated with an increase in the concentration of relevant short and branched‐chain esters and acetates, and a decrease in the concentration of phenolic substances. No enhancement of fermentation performance was observed in any of the trials. Overall, this work revealed the robustness of red wine fermentations to aeration. Conclusions: This work provides strong evidence that aeration does not alter the duration of either alcoholic or malolactic fermentation of red musts. Although there was no impact on fermentation performance, aeration did result in the production of wines with increased red fruit characters, and decreased astringency and reductive off‐odours. Significance of the Study: This work demonstrates aeration to be a useful oenological tool for the production of red wine and indicates that stylistic impact, rather than fermentation performance, is likely to be more pertinent to the adoption of red wine aeration. [ABSTRACT FROM AUTHOR]

Background and Aims: Winemakers utilise various remediation strategies for decreasing 'reductive' characters in wine. Remediation strategies, such as the addition of diammonium phosphate (DAP) during fermentation, copper fining, the addition of fresh lees or lees products to wine, and aeration of the must during and after fermentation, are commonly employed in an effort to prevent the formation or to remove undesirable volatile sulfur compounds. In this study, the relative effectiveness of five strategies for remediation of 'reductive' aroma was compared in a Shiraz wine. Methods and Results: At the onset of the development of 'reductive' aromas during Shiraz fermentation, each ferment was treated with a unique remediation strategy: DAP addition; macro‐oxygenation; copper fining; a combination of macro‐oxygenation and copper fining; or the addition of fresh lees from a donor wine. While a relatively small difference in volatile sulfur compounds was found between treatments, copper fining, lees and DAP addition produced wines with elevated 'reductive' characters at certain time‐points post‐bottling; while macro‐oxygenation or macro‐oxygenation with copper produced wines with a low sensory score for 'reduction'‐related attributes. Conclusions: Macro‐oxygenation during fermentation was the most effective remediation strategy. Lees addition, and to a lesser extent, copper fining and DAP addition, diminished fruit attributes and produced wines with noticeable 'reductive' characters. Significance of the Study: Macro‐oxygenation during fermentation produced wines with the lowest 'reduction'‐related attributes while enhancing 'fruity' attributes. This work also highlighted the compositional effects of each type of remediation treatment. [ABSTRACT FROM AUTHOR]

Background and Aims: Still wine contains a significant but sub‐saturated concentration of carbon dioxide (CO2) that remains following alcoholic fermentation. The concentration of CO2 can be adjusted by winemaking practices and may influence wine sensory properties. This study set out to define for the first time the effect of a sub‐saturated level of dissolved carbon dioxide (DCO2) on the taste, overall aroma, flavour and mouthfeel attributes of still white and red wine. Methods and Results: The concentration of DCO2 of two white and two red wines was adjusted to represent the range encountered in their respective wine types. Ethanol concentration of both wine types, the pH of the white wines and red wine tannin concentration were varied to assess the sensory implications of wine matrix interaction with DCO2. Differences in 'spritz' intensity were differentiable within the range of DCO2 concentration found in still white and red wines. A higher DCO2 concentration generally increased perceived sweetness and reduced bitterness and astringency perception. The DCO2 did not influence fruit aroma or flavour intensity and few consistent interactions between DCO2 and the wine matrix were observed. Conclusions: At still wine concentration DCO2 directly influences the taste and astringency of wine, but in a manner that is different from other beverage systems with a saturated level of CO2. Significance of the Study: The study is the first to explore the effect of a sub‐saturated (non‐sparkling) concentration of DCO2 on the aroma, taste, flavour and mouthfeel of wine and provides practical guidance as to how to modulate DCO2 in table wines to achieve a desired taste and mouthfeel. [ABSTRACT FROM AUTHOR]

Background and Aims: The total concentration of copper (Cu) in wine cannot be routinely measured without relatively expensive equipment, reagents and/or without labour‐intensive sample pretreatment. The following research describes an approach for the colorimetric measurement of total Cu in wine utilising a spectrophotometer and relatively cheap reagents. Method and Results: The proposed method is based on using bicinchoninic acid as the complexing chromophore for Cu. Copper was measured directly and rapidly in white wine, while a digestion of red wine was required. A key step for the analysis in the non‐digested white wine matrix was the addition of silver(I) to aid the dissociation of Cu in the wine from sulfide. For red and white wines, the limit of detection was 0.02 mg/L Cu, and the repeatability was 3 ± 1%. The accuracy of the method was assessed in terms of recovery experiments (102 ± 3%, n = 4), and also by comparing total Cu concentration in 84 wines determined by the colorimetric method with that obtained by inductively coupled plasma with optical emission spectroscopy (R2 = 0.95). Conclusions: The colorimetric determination of total Cu was successfully optimised and validated in white and red wines. Significance of the Study: The methodology will allow wineries and researchers to routinely measure total Cu concentration in wine with a spectrophotometer. [ABSTRACT FROM AUTHOR]

Background and Aims: The significance of oxygen in winemaking has been well established, but knowledge gaps exist regarding the extent and impact passive oxygenation has on chemical and sensory properties during the initial stages. Methods and Results: Using in‐press oxygen monitors, controlling oxygen exposure during the earliest stages of grape processing was shown to be highly effective. This work demonstrated that pressing management has far more impact on wine composition than handling management; the earliest and highest exposure to oxygen has the most profound impact on the composition of the resulting wine compared to the lower levels of repeated exposure typical of normal handling procedures. Furthermore, control of oxygen exposure during post‐pressing operations offers the possibility of modulating specific classes of compounds, described in sensory analysis as floral and confection. Conclusions: Significant modulation of aromatic, phenolic and protein profiles of wine occurred through controlling oxygen exposure during the earliest stages of grape processing. Significance of the Study: This work shows the possible stylistic potential and limitations of oxygen control, albeit with investment in press technology. The understanding of the relative influence of processing variables assessed in this work can be immediately applied by winemakers. [ABSTRACT FROM AUTHOR]

Background and Aims The study aimed to determine how fresh grape mesocarp modifies the extraction and composition of tannin under wine-like conditions. A further aim was to observe whether addition of anthocyanin during extraction exerted an effect on the concentration of recovered tannin. Methods and Results Fresh red grape berries were dissected into skin, mesocarp and seed. Different combinations of the berry components were extracted in model wine or fermented. Initial results indicated that mesocarp material bound seed tannin more selectively than skin tannin. Further experiments pointed towards a more complex system, whereby adsorption of tannin by mesocarp facilitated ongoing extraction of tannin from the skins. The effect exerted by mesocarp was potentially to increase the concentration gradient between skins and the liquid medium by the continuous removal of tannin. Under these conditions, both skin and seed tannin could be removed from extracts or wines by suspended mesocarp material. White grape skins or mesocarp were also extracted with the addition of a variable concentration of purified anthocyanin and found to facilitate the extraction of otherwise non-extractable tannin. This effect was observed to be greater for grape mesocarp than for white grape skins. Conclusions The concentration and composition of tannin were shown to be modified by the presence of mesocarp material. A role for anthocyanin in enhancing the extraction of tannin was confirmed. Significance of the Study The results show that multiple factors interact to influence tannin extraction and retention from grapes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background and Aims: Flavonols are present in Vitis vinifera L. wine grapes as glycosides and are found in wines in both their glycosidic and aglycone forms. Flavonols and their glycosides are important components in wine because of their impact on colour, taste and health properties. An assessment of the flavonols and flavonol glycosides present in a wide selection of Australian red and white wines ( n = 121 and 44, respectively) was undertaken. Methods and Results: Analyses were performed using HPLC, with compound identification being aided by HPLC-MS. In the red wines, quercetin and myricetin dominated the flavonol profile, and quercetin-3-glucuronide was by far the most abundant glycoside present. White wines had considerably lower levels of flavonols and their glycosides, in most cases, being below the detection limit of the HPLC method. Conclusions: There appeared to be no correlation between the flavonol profile and wine variety or region in either white or red wines. Contrary to literature reports of rutin in wine, rutin was not found in any of the wines we analysed, and spiking experiments showed rutin rapidly degraded to the aglycone quercetin. Furthermore, changes in elution order for some quercetin glycoside standards were observed depending upon the acid used in the mobile phase. Significance of the Study: This is the first time the flavonol contents of an extensive cross section of Australian wines have been reported. The concentrations are consistent with those reported in wines from other countries. In light of the instability of rutin in wine, critical review should be given to reports discussing its presence. [ABSTRACT FROM AUTHOR]