Katja Šuklje

Berry Shriveling Significantly Alters Shiraz (Vitis vinifera L.) Grape and Wine Chemical Composition

Berry shriveling is an often reported occurrence in the Shiraz (Vitis vinifera L.) cultivar. This study investigated the effect of berry shriveling occurring in a high yielding (18.6 ± 1.6 kg/vine) Shiraz vineyard in relation to a temporal investigation of grape and wine composition using three harvest dates. Berry shriveling resulted in delayed total soluble solids and amino acid accumulation into the berry, however differences between treatments diminished or became smaller by the third harvest date. Similarly, ethyl esters of fatty acids and higher alcohol acetates were lower in wines from shriveled berries from the first two harvests; anthocyanins were reduced in wines from shriveled berries at all harvest dates, whereas terpenes were unaltered. Wines made from shriveled berries had higher γ-nonalactone and β-damascenone concentrations. This study provides novel information on the chemical alterations of grapes and wines made from grapes affected by shriveling.

Clonal differences and impact of defoliation on Sauvignon blanc (Vitis vinifera L.) wines: a chemical and sensory investigation

BACKGROUND The aim of this study, performed on Sauvignon blanc clones SB11 and SB316, grafted on the same rootstock 101-14 Mgt (Vitis riparia × V. ruperstris) and grown at two adjacent vineyards, was two-fold: (1) to study wine chemical and sensory composition of both clones within an unaltered canopy; and (2) to determine the effect of defoliation (e.g. bunch microclimate) on wine chemical and sensory composition. RESULTS Orthogonal projection to latent structures discriminate analysis (OPLS-DA) was applied to the concentration profiles of volatile compounds derived from gas chromatography-mass spectrometry data. The loadings directions inferred that 3-isobutyl-2-methoxypyrazine (IBMP) discriminated control treatments (shaded fruit zone) of both clones from defoliation treatments (exposed fruit zone), whereas 3-sulfanyl-hexan-1-ol (3SH), 3-sulfanylhexyl acetate (3SHA), hexanol, hexyl hexanoate and some other esters discriminated defoliated treatments from the controls. The OPLS-DA indicated the importance of IBMP, higher alcohol acetates and phenylethyl esters, for discrimination of clone SB11 from clone SB316 irrespective of the treatment. Defoliation in the fruit zone significantly decreased perceived greenness in clone SB11 and elevated fruitier aromas, whereas in clone SB316 the effect of defoliation on wine sensory perception was less noticeable regardless the decrease in IBMP concentrations. CONCLUSION These findings highlight the importance of clone selection and bunch microclimate to diversify produced wine styles.

Investigation and Sensory Characterization of 1,4-Cineole: A Potential Aromatic Marker of Australian Cabernet Sauvignon Wine

This work reports the quantitation and sensory characterization of 1,4-cineole in red wine for the first time. A headspace-solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method was developed to quantitate 1,4-cineole and 1,8-cineole in 104 commercial Australian red wines. 1,4-Cineole was detected in all of the wines analyzed, with concentrations ranging from 0.023 to 1.6 μg/L. An important varietal effect was observed, with concentrations of 1,4-cineole in Cabernet Sauvignon wines (mean of 0.6 ± 0.3 μg/L) significantly higher than in Shiraz (0.07 ± 0.04 μg/L) and Pinot Noir (0.2 ± 0.2 μg/L) wines. Regional variations of both cineole isomer concentrations have been measured between wines originating from different Australian regions. Sensory studies demonstrated that the addition of 0.54 μg/L 1,4-cineole in a Cabernet Sauvignon wine, to produce a final concentration of 0.63 μg/L, was perceived significantly by a sensory panel (p < 0.05). Descriptive analyses revealed that 1,4-cineole and 1,8-cineole may contribute to the hay, dried herbs, and blackcurrant aromas reported in Australian Cabernet Sauvignon wines and may be potential markers of regional typicality of these wines.

Inactive dry yeast application on grapes modify Sauvignon Blanc wine aroma.

This study investigated the potential to improve wine aroma by applying two inactive dry yeast products (IDYs) at the onset of ripening on Sauvignon Blanc grapes. Both products led to increased reduced glutathione concentrations in the grape juice and corresponding wines, as well as differences in individual higher alcohol acetates (HAAs) and ethyl esters of straight chain fatty acids (EEFAs) at the end of fermentation. After two months of storage, a significantly slower decrease of EEFAs and to a lesser extent of HAAs was found for wines made from grapes with IDY applications. These wines also resulted in significantly slower synthesis of ethyl esters of branched acids, whereas varietal thiols were altered in a product-specific manner. The modifications in the wine chemical composition were also sensorially corroborated. This study showed that vineyard additions of IDY products directly on the grapes at the onset of ripening have a subsequent benefit to the production and preservation of aroma in wines.

Vitis vinifera root and leaf metabolic composition during fruit maturation: implications of defoliation

Grapevine (Vitis vinifera) roots and leaves represent major carbohydrate and nitrogen (N) sources, either as recent assimilates, or mobilized from labile or storage pools. This study examined the response of root and leaf primary metabolism following defoliation treatments applied to fruiting vines during ripening. The objective was to link alterations in root and leaf metabolism to carbohydrate and N source functioning under conditions of increased fruit sink demand. Potted grapevine leaf area was adjusted near the start of véraison to 25 primary leaves per vine compared to 100 leaves for the control. An additional group of vines were completely defoliated. Fruit sugar and N content development was assessed, and root and leaf starch and N concentrations determined. An untargeted GC/MS approach was undertaken to evaluate root and leaf primary metabolite concentrations. Partial and full defoliation increased root carbohydrate source contribution towards berry sugar accumulation, evident through starch remobilization. Furthermore, root myo-inositol metabolism played a distinct role during carbohydrate remobilization. Full defoliation induced shikimate pathway derived aromatic amino acid accumulation in roots, while arginine accumulated after full and partial defoliation. Likewise, various leaf amino acids accumulated after partial defoliation. These results suggest elevated root and leaf amino N source activity when leaf N availability is restricted during fruit ripening. Overall, this study provides novel information regarding the impact of leaf source restriction, on metabolic compositions of major carbohydrate and N sources during berry maturation. These results enhance the understanding of source organ carbon and N metabolism during fruit maturation.

Vitis vinifera berry metabolic composition during maturation: implications of defoliation.

Leaves are an important contributor toward berry sugar and nitrogen (N) accumulation, and leaf area, therefore, affects fruit composition during grapevine (Vitis vinifera) berry ripening. The aim of this study was to investigate the impact of leaf presence on key berry quality attributes in conjunction with the accumulation of primary berry metabolites. Shortly after the start of véraison (berry ripening), potted grapevines were defoliated (total defoliation and 25% of the control), and the accumulation of berry soluble solids, N and anthocyanins were compared to that of a full leaf area control. An untargeted approach was undertaken to measure the content in primary metabolites by gas chromatography/mass spectrometry. Partial and full defoliation resulted in reduced berry sugar and anthocyanin accumulation, while total berry N content was unaffected. The juice yeast assimilable N (YAN), however, increased upon partial and full defoliation. Remobilized carbohydrate reserves allowed accumulation of the major berry sugars during the absence of leaf photoassimilation. Berry anthocyanin biosynthesis was strongly inhibited by defoliation, which could relate to the carbon (C) source limitation and/or increased bunch exposure. Arginine accumulation, likely resulting from reserve translocation, contributed to increased YAN upon defoliation. Furthermore, assessing the implications on various products of the shikimate pathway suggests the C flux through this pathway to be largely affected by leaf source limitation during fruit maturation. This study provides a novel investigation of impacts of leaf C and N source presence during berry maturation, on the development of key berry quality parameters as underlined by alterations in primary metabolism.

Late-Season Shiraz Berry Dehydration That Alters Composition and Sensory Traits of Wine

Late-season berry dehydration (LSD) is a common occurrence in Shiraz grapes, particularly those grown in hot climates. LSD results in significant yield reductions; however, the effects on wine composition and sensory characteristics are not well-documented. Wines made of 100% nonshriveled clusters (control) were related to red fruit flavors by the sensory panel, whereas wines made of 80% shriveled clusters (S-VCT) were perceived as more alcoholic and associated with dark fruit and dead/stewed fruit characters. The latter wines also resulted in higher concentrations of massoia lactone and γ-nonalactone, compounds known to contribute to prune and stewed-fruit aromas. Wines made of shriveled grapes were also characterized by an increase in C6-alcohols and a decrease in esters, whereas wine terpenoids were altered compound-specific. An increase in orange pigments and wine chemical age in S-VCT wines indicated faster oxidative aging compared to the control. LSD appeared to alter final wine composition directly but also appeared to influence yeast metabolism, potentially due to an alteration of the composition of lipids in the grape juice. This study emphasized the relevance of sorting shriveled and nonshriveled berries for final wine chemical composition and wine style.