Reinhard Eder

Harvest timing is an important management factor associated with the volatile composition of wine. This one-vintage study investigated selected free aroma-related volatile compounds in Blaufränkisch and Pinot Noir wines produced under standardised microvinification from grapes harvested at early, standard and late maturity-related stages in four commercial vineyards. Free volatile polyfunctional thiols, six-carbon (C₆) alcohols, free monoterpenes, rotundone and free 13-carbon (C₁₃) norisoprenoids were quantified using gas chromatographic methods, and data were evaluated using exploratory univariate and multivariate statistics. Harvest-stage responses were compound-specific and depended on the investigated grape-variety/regional sample sets. The concentration of 1-hexanol generally decreased with advancing harvest stage, whereas 3-sulfanylhexan-1-ol (3-SH) tended to increase across several vineyard origins. An exploratory pooled correlation between 1-hexanol and 3-SH was weakly negative, indicating only a limited association between the two compounds in bottled wines. Free monoterpenes and free C₁₃-norisoprenoids showed non-linear, compound-dependent patterns, while rotundone showed no consistent overall harvest-stage response. Principal component analysis (PCA) separated the wines mainly according to grape-material background, with additional harvest-stage-related structuring. Overall, under the specific conditions of this one-vintage study, operationally defined maturity-related harvest timing was associated with compound- and background-dependent changes in selected free aroma-related volatile compounds in the investigated red wines.

Zusammenfassung: Ziel dieser Arbeit war es zu testen, ob das Verfahren der Membrandestillation mit hydrophoben Membranen für österreichische Verhältnisse ein taugliches Verfahren ist, um den Alkoholgehalt in alkoholreichen Weinen zu senken und das typische, fruchtig-frische Geschmacksbild wieder zu erlangen. Zu diesem Zweck wurden früh und spät geerntete Trauben der Sorte Grüner Veltliner einerseits unangereichert (10,9 %vol bzw. 12,1 %vol) und andererseits auf 13,3 %vol bzw. 14,3 %vol angereichert vergoren und die angereicherten Weine dann in Schritten von jeweils minus 0,7 %vol um bis zu 2,1 %vol entalkoholisiert. Bei der Alkoholreduktion mittels Membrandestillation mit hydrophoben Membranen wurde auch der Einfluss der Begasung des Strippingswassers mit Stickstoff bzw. Kohlendioxid auf die Produktqualität bestimmt, wobei sich herausstellte, dass Kohlendioxid deutlich fruchtigere, frischere Weine ergab. Chemische Analysen der Weine ergaben, dass die Gehalte der Zucker und Säuren infolge der Membrandestillation nicht verändert wurden, während hingegen bei Ethylacetat Abnahmen zwischen 14–44 %, bei Methanol zwischen 6–28 %, und bei höheren Alkoholen feststellbar waren. Die Verringerungen der flüchtigen Verbindungen waren proportional dem Grad der Entalkoholisierung, wirkten sich aber nicht qualitätsmindernd aus. Die sensorische Beurteilung der Weine erfolgte durch amtlich geschulte Weinkoster, wobei bei der Bewertung nach dem 20-Punkteschema immer ein entalkoholisierter Wein mit CO ₂ -gesättigtem Strippingwasser als Bester bewertet wurde, und zwar bei dem früh gelesenen, angereicherten Grünen Veltlinern (Ausgangsalkoholgehalt: 13,3 %vol) die auf 12,5 %vol teilentalkoholisierte Variante und beim spät gelesenen, angereichterten Grünen Veltliner (Ausgangsalkoholgehalt: 14,3 %vol) die auf 13,5 %vol alkoholreduzierte Variante. Auch bei der deskriptiven Bewertung wurden Weine mit einer Reduktion des Alkoholgehalts um 0,8 %vol bis 1,5 %vol bei der Hauptkomponentenanalyse in den Bereichen fruchtiger Geruch und sortentypischer Geschmack sowie guter Gesamteindruck sehr gut bewertet. Somit kann festgestellt werden, dass die Alkoholreduktion mit Membrandestillation und hydrophoben Membranen aufgrund der sehr guten erzielten Produktqualitäten und den bekannt geringen Investitions- und Betriebskosten sowie der einfachen Bedienung eine sehr gute Möglichkeit für das moderne, zukunftsfitte Alkoholmanagement darstellt.

In response to growing consumer expectations for greater diversity and novel flavour profiles in wines, this study explored the use of alternative wood species in oenology. The effects of six alternative wood species – sweet chestnut, common hazel, Robinia , blackcurrant, vineyard peach, and grapevine – on Austrian Vitis vinifera L. cv. Grüner Veltliner wine were examined after a 98‐day contact period using both toasted and untoasted wood chips. The aim was to characterise the similarities of these alternative wood species to traditionally used oak. A comprehensive analytical profiling was conducted, quantifying over 50 wood‐associated compounds, including hydroxycinnamic and benzoic acids, ellagitannins, lactones, carbonyl compounds and volatile phenols. Currently, only oak and sweet chestnut are approved by the International Organisation of Vine and Wine for oenological applications, with wood chips permitted exclusively from the genus Quercus . Based on the results, toasted sweet chestnut was the most promising alternative species for use as wood chips. It enhanced the wine colour intensity more effectively than oak, while its phenolic composition, particularly catechin levels and hydroxycinnamic acids, aligned moderately with oak. Furthermore, wine treated with toasted sweet chestnut presented comparable concentrations of vescalagin and castalagin. The similar levels of carbonyl compounds, such as furfural, further underlined its suitability. Although volatile phenol levels, including vanillin, exceeded those of oak, wine treated with toasted sweet chestnut remained comparable in its overall composition. Based on these findings, toasted sweet chestnut is recommended for approval as wood chips, although additional sensory and toxicological studies are necessary to substantiate this recommendation.

This study analyzed the phenolic compounds, organic acids, sugars, and antioxidant activity in different conventional apple cultivars (Malus domestica) from the Serbian market. Polyphenol profiles, sugars, and organic acid contents were analyzed by HPLC, and antioxidant activity was examined by DPPH and FRAP. Notable findings included variations in phenolic compound presence, with certain compounds detected only in specific cultivars. ‘Red Jonaprince’ exhibited the highest arbutin (0.86 mg/kg FW) and quercetin-3-rhamnoside content (22.90 mg/kg FW), while ‘Idared’ stood out for its gallic acid content (0.22 mg/kg FW) and ‘Granny Smith’ for its catechin levels (21.19 mg/kg FW). Additionally, malic acid dominated among organic acids, with ‘Granny Smith’ showing the highest content (6958.48 mg/kg FW). Fructose was the predominant sugar across all cultivars. Chemometric analysis revealed distinct groupings based on phenolic and organic acid profiles, with ‘Granny Smith’ and ‘Golden Delicious’ exhibiting unique characteristics. Artificial neural network modeling effectively predicted antioxidant activity based on the input parameters. Global sensitivity analysis highlighted the significant influence of certain phenolic compounds and organic acids on antioxidant activity.

Many varietal aromas of wine are located in the berry skin. In the present study, we evaluated four important Austrian grape varieties: Grüner Veltliner, Sauvignon Blanc, Traminer, and Pinot Blanc. We assessed whether prefermentation skin contact, fermentation with the skin (only for Grüner Veltliner), and stabulation (lees stirring; only for Sauvignon Blanc, Traminer, and Pinot Blanc) could enhance the varietal aromas of the different grape cultivars. The aim was to intensify the varietal aromas without extracting the undesirable phenols. We performed a detailed analytical characterisation of approximately 100 volatile and phenolic compounds as well as a sensory characterisation. Although mash fermentation significantly increased the spicy aromas of Grüner Veltliner, which are affected by climate change (especially the sesquiterpene rotundone), it markedly decreased the fruitiness and increased the bitterness; therefore, it cannot be recommended for this cultivar. For Sauvignon Blanc, stabulation is a possible option; the varietal aromas (thiols and methoxypyrazines) were increased in the final wines of these variants. For Pinot Blanc and Traminer, prefermentation skin contact yielded the best results: for Traminer, it produced the highest content of monoterpenes (especially z-rose oxide), and for Pinot Blanc, it produced the highest content of ethyl esters. To summarise, stabulation will not completely replace classic skin contact, and mash fermentation is certainly not an alternative for the production of standard Grüner Veltliner wine. However, additional investigations are necessary with regard to other grape varieties, terroirs, and vintages before we can make final recommendations.

Current research results indicate that the intake of flavonols could potentially have positive effects on the health of the human organism. In the study presented here, the content of four health-relevant flavonols - namely myricetin, quercetin, isorhamnetin and kaempferol - was analysed in wines vinified with and without mash fermentation from white and red grapes of Austrian grape varieties. The glycosidically bound flavonols were broken down with the help of acid hydrolysis and, like the free flavonols, quantified by a specially developed HPLC method. In the course of the investigation it was found that white wines without mash fermentation can also have conjugated myricetin (0.25 mg/l) and quercetin (0.86 mg/l). The highest concentrations of conjugated myricetin (7.95 mg/l) and quercetin (5.81 mg/l) were identified in red wines with mash fermentation. Kämpferol (1.20 mg/l) and isorhamnetin (3.21 mg/l) could be detected mainly in wines from red grapes. There was a correlation between flavonol concentrations and mash fermentation, with red wines showing higher concentrations than orange wines.

This study aimed to improve the understanding of 2-aminoacetophenone (2-AAP) formation in white wines, a compound responsible for atypical ageing (ATA) associated with a rapid loss of white wine fruity aroma and to the development of unpleasant odors. Two surveys performed in 139 white wines from Central Europe investigated the varietal effect on wine tendency to form 2-AAP during ageing. The role of some antioxidants and important transition metal ions present in wine (Fe, Cu and Mn) in the formation of 2-AAP was also investigated. The surveys highlighted that Muscat and Riesling wines showed significantly higher concentrations of 2-AAP than Chardonnay and some other regional varieties found in Central Europe such as Grüner Veltliner, Welschriesling and Zelen. The origin of such varietal effects could not be related to the level of any 2-AAP precursor. On the other hand, some of the important wine matrix effects were highlighted. A certain variability in capacity of different antioxidants to limit 2-AAP formation was observed. Supplementations of commercial tannins in wines tended to be more efficient than glutathione in preserving wines from the formation of 2-AAP. Transition metal ions significantly impacted 2-AAP synthesis through complex interactions. Generally, Fe and Mn tended to promote formation of 2-AAP, while the presence of Cu limited it. The higher concentration of transition metal ions significantly improved the efficiency of antioxidants to reduce 2-AAP formation. Further studies investigating the origin of varietal effects and the complex matrix effects involving metal ions and antioxidants in 2-AAP production are warranted.