High performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS-MS) for the quantification of L-kynurenine and indole-3-acetic acid in grape must by isotope dilution assay

Isotope dilution assay was used for the qualitative and quantitative analysis of L-kynurenine and indole-3-acetic acid in grape must. After solid phase extraction, highest selectivity and sensitivity was achieved by high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS-MS) using selected reaction monitoring (SRM). In the 24 samples under study, the amounts of L-kynurenine and indole-3-acetic acid ranged from 0 to 94 mu g.l-1 and from 20 to 380 mu g.l-1, respectively. These compounds are considered as potential precursors of 2-aminoacetophenone, causing the ''untypical aging off-flavour'' in Vitis vinifera white wines

Towards a scientific interpretation of the terroir concept: plasticity of the grape berry metabolome

BACKGROUND: The definition of the terroir concept is one of the most debated issues in oenology and viticulture. The dynamic interaction among diverse factors including the environment, the grapevine plant and the imposed viticultural techniques means that the wine produced in a given terroir is unique. However, there is an increasing interest to define and quantify the contribution of individual factors to a specific terroir objectively. Here, we characterized the metabolome and transcriptome of berries from a single clone of the Corvina variety cultivated in seven different vineyards, located in three macrozones, over a 3-year trial period. RESULTS: To overcome the anticipated strong vintage effect, we developed statistical tools that allowed us to identify distinct terroir signatures in the metabolic composition of berries from each macrozone, and from different vineyards within each macrozone. We also identified non-volatile and volatile components of the metabolome which are more plastic and therefore respond differently to terroir diversity. We observed some relationships between the plasticity of the metabolome and transcriptome, allowing a multifaceted scientific interpretation of the terroir concept. CONCLUSIONS: Our experiments with a single Corvina clone in different vineyards have revealed the existence of a clear terroir-specific effect on the transcriptome and metabolome which persists over several vintages and allows each vineyard to be characterized by the unique profile of specific metabolites.Andrea Anesi, Matteo Stocchero, Silvia Dal Santo, Mauro Commisso, Sara Zenoni, Stefania Ceoldo, Giovanni Battista Tornielli, Tracey E. Siebert, Markus Herderich, Mario Pezzotti and Flavia Guzz

Screening for potential wine pigments in red wine using tandem mass spectrometry

Yoji Hayasaka, Robert E. Asenstorfer and Markus Herderic

Patterns of within-vineyard spatial variation in the ‘pepper’ compound rotundone are temporally stable from year to year

Background and Aims: Within‐vineyard variation in the concentration of grape berry rotundone has been shown to be spatially structured and related to variation in the land (soil, topography) underlying the vineyard, although its temporal stability has not been evaluated. Our aim here was therefore to ascertain whether patterns of rotundone variation were stable from year to year. This is an important aspect in understanding and exploiting terroir on a vineyard‐scale as it informs how targeted management might take advantage of the variation to the benefit of both grapegrowers and winemakers. It also facilitates targeted research into the biophysical factors that may be critical to the formation of rotundone in grapes. Methods and Results: Immediately prior to the commercial harvest of a 6.1 ha vineyard block in the Grampians region of Victoria, 177 geo‐referenced samples of grapes were collected in each of three seasons (2012, 2013 and 2015) and analysed for their rotundone concentration. The mean berry rotundone concentration varied 40‐fold between seasons, yet spatial analysis of maps of rotundone variation produced for each year indicated that the patterns of spatial variation were stable across seasons. Conclusions: Irrespective of the seasonal factors which affect the mean concentration of berry rotundone, variation in the land (soil, topography) underlying the vineyard is a consistent driver of within‐vineyard variation in this important grape‐derived flavour and aroma compound. Significance of the Study: This work suggests that targeted vineyard management strategies, including selective harvesting, may be used to manipulate wine style – in this case, the pepperiness of cool climate Shiraz wines. It also suggests that further study of the relationships between the environment and berry composition is warranted in pursuit of a more robust understanding of terroir.R.G.V. Bramley, T.E. Siebert, M.J. Herderich, M.P. Krsti

Aroma precursors in grapes and wine: flavor release during wine production and consumption

Pioneering investigations into precursors of fruity and floral flavors established the importance of terpenoid and C13-norisoprenoid glycosides to the flavor of aromatic wines. Nowadays flavor precursors in grapes and wine are known to be structurally diverse, encompassing glycosides, amino acid conjugates, odorless volatiles, hydroxycinnamic acids, and many others. Flavor precursors mainly originate in the grape berry but also from oak or other materials involved in winemaking. Flavors are released from precursors during crushing and subsequent production steps by enzymatic and nonenzymatic transformations, via microbial glycosidases, esterases, C-S lyases, and decarboxylases, and through acid-catalyzed hydrolysis and chemical rearrangements. Flavors can also be liberated from glycosides and amino acid conjugates by oral microbiota. Hence, it is increasingly likely that flavor precursors contribute to retronasal aroma formation through in-mouth release during consumption, prompting a shift in focus from identifying aroma precursors in grapes to understanding aroma precursors present in bottled wine.Mango Parker, Dimitra L. Capone, I. Leigh Francis and Markus J. Herderic

Occurrence of 2-Acetyl-1-Pyrroline in Mousy Wines

The potent flavour compound 2-acetyl-1-pyrroline (1) was identified for the first time in wines spoiled by mousy taint. Identification was verified by comparison of GC and GC-MS data with those of authentic reference material. GC-SNEFF analysis of (1) further confirmed its intense mousy aroma

Chemometrics and visible-near infrared spectroscopic monitoring of red wine fermentation in a pilot scale

The modern wine industry needs tools for process control and quality assessment in order to better manage fermentation or bottling processes. During wine fermentation it is important to measure both substrate and product concentrations (e.g. sugars, phenolic compounds), however, the analysis of these compounds by traditional means requires sample preparation and in some cases several steps of purification are needed. The combination of visible/near-infrared (Vis/NIR) spectroscopy and chemometrics potentially provides an ideal solution to accurately and rapidly monitor physical or chemical changes in wine during processing without the need for chemical analysis. The aim of this study was to assess the possibility of combining spectral and multivariate techniques, such as principal component analysis (PCA), discriminant partial least squares (DPLS), or linear discriminant analysis (LDA), to monitor time-related changes that occur during red wine fermentation. Samples (n = 652) were collected at various times from several pilot scale fermentations with grapes from either Cabernet Sauvignon or Shiraz varieties, over three vintages (2001-2003) and scanned using a monochromator instrument (Foss-NIRSystems 6500, Silver Spring, MD) in transmission mode (400-2,500 nm). PCA was used to demonstrate consistent progressive spectral changes that occur through the time course of the fermentation. LDA using PCA scores showed that regardless of variety or vintage, samples belonging to a particular time point in fermentation could be correctly classified. This study demonstrates the potential of Vis/NIR spectroscopy combined with chemometrics, as a tool for the rapid monitoring of red wine fermentation

Berry phenolics in cabernet sauvignon (Vitis vinifera L.) during late-stage ripening

The trends in changes to berry weight and phenolic concentrations of Cabernet Sauvignon berries during the later stages of berry ripening from different pruning and irrigation treatments were examined. Maturity was defined as total soluble solids (TSS). Berry phenolic concentration was examined using a 50% ethanol extract of grape homogenate, which is commonly used in the Australian wine industry to measure grape anthocyanins. Berry weight and berry composition were examined at three maturity stages over three vintages. Three pruning treatments were established with two irrigation treatments superimposed to provide a wide range of berry sizes and phenolic measures. Increasing maturity had consistent effects on berry weight across vintages and on berry phenolic composition within vintages. In a commercial context, peak total anthocyanin concentration and content might be a useful guide to harvest decisions, but in this study total phenolic and tannin measures did not assist in these decisions, as these measures were highest at higher than commercially acceptable TSS. In a research context, this information can be useful in determining the pattern of anthocyanin, total phenolic, and tannin accumulation and decline and would be useful in conjunction with wine measures of these parameters to determine relationships between berry and wine composition. Pruning treatments were associated with consistent effects on berry weight across vintages and maturity stages and consistent effects on total anthocyanin and total phenolic concentrations, but not on tannin concentrations. Irrigation effects were less consistent within or between vintages and the effects were highly dependent on vintage conditions.Helen E. Holt, Warren Birchmore, Markus J. Herderich, and Patrick G. Ilan

The effect of Saccharomyces cerevisiae and Saccharomyces bayanus yeast on colour properties and pigment profiles of a Cabernet Sauvignon red wine

Red wine was made from the same batch of Cabernet Sauvignon grapes but with two different yeasts, Saccharomyces cerevisiae (SC) or Saccharomyces bayanus (SB). The colour properties and pigment profiles of SC and SB wines were compared at 8 days and 387 days after yeast inoculation. Grape anthocyanin concentration was found to be lower in SB wines than in SC wines at day 8 and 387, but SB wine exhibited greater wine colour density, a* and b*. The anthocyanin concentration did not correlate with wine colour density. The levels of pigmented polymers and SO2 non-bleachable pigments were found to be higher in SB wine at day 387, demonstrating that the formation of stable pyranoanthocyanins and pigmented polymers was enhanced by SB yeast. Electrospray mass spectrometry was used for the compositional analysis of pyranoanthocyanins, and direct and ethyl-bridged linked condensation dimers of malvidin 3-0-glucoside (MvG) with flavanols (catechin or epicatechin). The data demonstrated that the formation of acetaldehyde-mediated pigments was enhanced by the use of the SB yeast. The compositional analysis suggested that the differences in colour properties and pigment profiles of SC and SB wines were largely due to the greater production of acetaldehyde-mediated pigments by the use of SB yeast.Yoji Hayasaka, Maria Birse, Jeffrey Eglinton and Markus Herderic