Impact of light on protective fractions of Cu in white wine: Influence of oxygen and bottle colour.

Cu(II)-organic acid (fraction I) and Cu(I)-thiol (fraction II) complexes can suppress sulfhydryl off-aromas in wine. This study investigated the impact of light exposure on the protective fractions of Cu of bottled white wine. Fluorescent light-exposed Chardonnay with two initial concentrations of dissolved oxygen (0.5 and 10 mg/L) was stored in different coloured bottles and concentrations of Cu fractions and riboflavin, a photo-initiator at 370-440 nm, were measured during 110 days storage. Light-exposed wines with lower oxygen concentrations resulted in a 100-fold decrease in the Cu fraction I half-life, and a 60-fold decrease for Cu fractions I and II combined. The half-life for Cu fraction I decay during light exposure was extended 30-fold with the use of brown compared to flint glass. Light exposure can rapidly exhaust the protective Cu fractions in wine, and bottles with less light transmission below 440 nm can slow this loss.

Ascorbic acid addition to rosé: Impact on the oxidative and reductive development of bottled wine.

The impact of ascorbic acid on the oxidative and reductive development of rosé wine during bottle ageing has not been previously established. A rosé wine that contained 0.25 mg/L of Cu was bottled with levels of 0, 50 or 500 mg/L of ascorbic acid and different total packaged oxygen concentrations (3 and 17 mg/L), and was stored for 15 months at 14 °C in darkness. Ascorbic acid increased the first-order oxygen consumption rate from 0.030 ± 0.001 to 0.040 ± 0.001 days-1, and decreased the mole ratio of total SO2 consumed to oxygen consumed from 1.0:1 to 0.7:1. Although ascorbic acid did accelerate the loss of a Cu form that can suppress reductive aromas, it did not induce reductive aromas. These results indicate that ascorbic acid can accelerate the removal of oxygen from bottled rosé wine while maintaining higher concentrations of sulfur dioxide, however, it did not promote reductive development.

Suppression of reductive characters in white wine by Cu fractions: Efficiency and duration of protection during bottle aging.

Cu in wine can suppress sulfidic-odours, but the active forms and duration of protection are uncertain. Additions of 0, 0.3 or 0.6 mg/L Cu(II) were made to Chardonnay and Pinot Grigio at bottling. Throughout a 12- or 14-month storage period, Cu fractions were determined by colorimetry, and sulfhydryl compounds by gas chromatography with sulfur chemiluminescence detection. After Cu(II) addition, the dominant Cu fractions were associated with Cu(II)-organic acids (fraction I) and Cu(I)-thiol complexes (fraction II), and over 8-months their concentrations gradually fell below 0.015 mg/L. During this time, a fraction of Cu, predominantly attributed to sulfide-bound Cu, increased in concentration. Suppression of free hydrogen sulfide was assured when the combined Cu fractions I and II concentrations were above 0.015 mg/L, while free methanethiol suppression required Cu fraction I concentration above 0.035 mg/L. Decay rates for Cu fractions demonstrated that the duration that Cu can actively suppress sulfidic odours is wine-dependent.

Changes in Red Wine Composition during Bottle Aging: Impacts of Grape Variety, Vineyard Location, Maturity, and Oxygen Availability during Aging.

This work investigated the influence of grape variety, vineyard location, and grape harvest maturity, combined with different oxygen availability treatments, on red wine composition during bottle aging. Chemometric analysis of wine compositional data (i.e., wine color parameters, SO2, metals, and volatile compounds) demonstrated that the wine samples could be differentiated according to the different viticultural or bottle-aging factors. Grape variety, vineyard location, and grape maturity showed greater influence on wine composition than bottle-aging conditions. For most measured wine compositional variables, the evolution patterns adopted from the viticultural factors were not altered by oxygen availability treatment. However, contrasting evolution patterns for some variables were observed according to specific viticultural factors, with examples including dimethyl sulfide, phenylacetaldehyde, maltol, and ß-damascenone for vineyard locations, 2-methylbutanal, 1,4-cineole, and linalool for grape variety, and methanethiol, methional, and homofuraneol for grape maturity.

Regional Discrimination of Australian Shiraz Wine Volatome by Two-Dimensional Gas Chromatography Coupled to Time-of-Flight Mass Spectrometry.

Shiraz wine volatomes from two Australian geographical indications (GIs), that is, Orange and Riverina, were compared using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Shiraz wines were made in triplicate from grapes harvested at two harvest dates from six vineyards in the two GIs. A total of 133 compounds showed a significant trend between wines from the cooler Orange GI and warmer Riverina. Compounds associated with wines from the cooler climate were grape-derived volatiles, such as monoterpenes, sesquiterpenes, green leaf volatiles, and some norisoprenoids. Fermentation-derived compounds, such as esters and S-containing compounds, showed no specific trend related to grape origin. In addition, wines could be also clearly separated according to the harvest date, irrespective of the climate, with C6 compounds, higher alcohol acetates, and other esters contributing utmost to the differentiation of samples, whereas terpenoids and norisoprenoids did not have an influence. This study demonstrated the plasticity of wine volatome related to grape origin and also the maturity level (harvest date), irrespective of climate.

Unravelling wine volatile evolution during Shiraz grape ripening by untargeted HS-SPME-GC × GC-TOFMS.

The influence of grape maturity on wine volatome was investigated using HS-SPME-GC × GC-TOFMS. Shiraz wines were made from grapes harvested from four different vineyards from two berry maturity levels. A total of 1276 putative compounds were detected in at least one of the wine samples and 175 showed significant trends related to grape maturity. The first two dimensions of the Principal component analysis accounted for 57% of the variation and separated the samples according to the harvest date. Wines from the first harvest date were characterised by an abundance of lipoxygenase derived compounds, norisoprenoids and sulfur-containing compounds whereas a significant increase in some acetate esters was observed in wines produced from the more mature grapes. This study demonstrated a common evolution of grape volatiles for Shiraz inside the same mesoclimate. During the late ripening stage of the grape, a direct nexus between sugar concentration and wine volatile evolution was not observed.

A GC-MS untargeted metabolomics approach for the classification of chemical differences in grape juices based on fungal pathogen.

Fungal bunch rot of grapes leads to production of detrimental flavour compounds, some of which are well characterised but others remain unidentified. The current study uses an untargeted metabolomics approach to classify volatile profiles of grape juices based on the presence of different fungal pathogens. Individual grape berries were inoculated with Botrytis cinerea, Penicillium expansum, Aspergillus niger or A. carbonarius. Grape bunches were inoculated and blended with healthy fruit, to provide 10% (w/w) infected juice. Juices from the above sample batches were analysed by GC/MS. PLS-DA of the normalised summed mass ions indicated sample classification according to pathogen. Compounds identified from those mass ion matrices that had high discriminative value for classification included 1,5-dimethylnaphthalene and several unidentified sesquiterpenes that were relatively higher in B. cinerea infected samples. A. niger and A. carbonarius samples were relatively higher in 2-(4-hexyl-2,5-dioxo-2,5-dihydrofuran-3-yl)acetic acid, while P. expansum samples were higher in γ-nonalactone and m-cresol.

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.

A comparative study of partial dealcoholisation versus early harvest: Effects on wine volatile and sensory profiles.

Two Verdelho and Petit Verdot wines were produced from sequential harvests of grapes. The alcohol concentration of early harvest (EH) and late harvest (LH) wines were respectively 9% and 13.5% v/v for Verdelho, and 10.5% and 13% v/v for Petit Verdot. LH wines were dealcoholised to match the same alcohol level of EH samples using a combined reverse osmosis-evaporative perstraction process. In dealcoholised wines, there was a decrease in volatile compounds (esters particularly) compared to LH treatments. For both varieties, the sensory attribute ratings for overall aroma intensity and alcohol mouthfeel also decreased following dealcoholisation. Dealcoholised wines were distinctively different from both LH and EH wines even though these wines had similar alcohol level to EH wines. When dealcoholisation is considered for high-alcohol wines, it is important to consider that membrane effects can significantly change depending on the wine non-volatile matrix composition and the level of alcohol reduction required.

Volatile and sensory profiling of Shiraz wine in response to alcohol management: comparison of harvest timing versus technological approaches.

The aim of this study was to compare the volatile and sensory profiles of Australian Shiraz red wines produced by several methods to achieve alcohol concentrations of 10.5 and 13.5% v/v. These levels were considerably lower contents than the commercial wine (16-17% v/v) that was produced from this vineyard site. Wines were produced by: (i) harvest timing (19.3, 24 and 29.3 Brix); (ii) blending equal proportions of early harvest (19.3 Brix) and late harvest wines (29.3 Brix); and (iii) dealcoholization using reverse osmosis followed by a membrane contactor. Dealcoholization caused a significant loss of volatile compounds, particularly esters, while the blending treatment had an averaging effect on most analytes. Sensory descriptive analysis of treatments with 10.5% v/v alcohol showed that the perception of the herbaceous attribute was more intense in the early harvest wines in comparison to the dealcoholized wines, while those of dark fruit, raisin/prune, astringency and alcohol were lower. No sensory differences were found amongst the 13.5% v/v wines, except for alcohol. Sensory and compositional data were modelled by means of Common Dimension (ComDim) multi-block analysis and indicated which chemical components are important to the perceived wine sensory properties. Insights from this study will provide knowledge that may be applied to control or moderate both unripe sensory attributes in addition to a deficiency of ripe fruit aromas or mouthfeel characteristics in reduced-alcohol red wines.

Harvesting and blending options for lower alcohol wines: a sensory and chemical investigation.

BACKGROUND: Lower alcohol wines often have a poor reputation among consumers, in part due to their unsatisfactory flavours such as reduced overall aroma intensity or herbaceous characters. The aim of this study, performed on Verdelho and Petit Verdot, was to quantify the effectiveness of a monovarietal blend in which wines made from less ripe grapes were blended with an equivalent volume of a wine vinified from riper fruit to produce wines with a lower alcohol content and desirable ripe fruit flavours. RESULTS: Eleven and 13 attributes, for Verdelho and Petit Verdot, respectively, were selected during sensory descriptive analysis. Intensities of perceived 'acidity', 'sweetness' and 'alcohol' attributes were significantly different (P ≤ 0.05) between the blend (8.8 ± 0.1% v/v) and mature Verdelho (10.3 ± 0.1% v/v) wines, while no significant differences were found between the Petit Verdot blend (11.0 ± 0.1% v/v) and mature (12.6 ± 0.2% v/v) treatments. Volatile composition of wines was assessed using HS-SPME-GC-MS. Partial least square regression suggested relationships between sensory descriptors and chemical attributes in the wines, as well as the modifications of sensory and compositional profiles following blending. CONCLUSIONS: The blending practice described allowed the production of wines with lower alcohol content while retaining similar sensory profiles of the later harvested, riper fruit wines. © 2017 Society of Chemical Industry.

Changes in volatile composition and sensory attributes of wines during alcohol content reduction.

A desirable sensory profile is a major consumer driver for wine acceptability and should be considered during the production of reduced-alcohol wines. Although various viticultural practices and microbiological approaches show promising results, separation technologies such as membrane filtration, in particular reverse osmosis and evaporative perstraction, in addition to vacuum distillation, represent the most common commercial methods used to produce reduced-alcohol wine. However, ethanol removal from wine can result in a significant loss of volatile compounds such as esters (ethyl octanoate, ethyl acetate, isoamyl acetate) that contribute positively to the overall perceived aroma. These losses can potentially reduce the acceptability of the wine to consumers and decrease their willingness to purchase wines that have had their alcohol level reduced. The change in aroma as a result of the ethanol removal processes is influenced by a number of factors: the type of alcohol reduction process; the chemical-physical properties (volatility, hydrophobicity, steric hindrance) of the aroma compounds; the retention properties of the wine non-volatile matrix; and the ethanol level. This review identifies and summarises possible deleterious influences of the dealcoholisation process and describes best practice strategies to maintain the original wine composition. © 2016 Society of Chemical Industry.

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.

Influence of Grape Composition on Red Wine Ester Profile: Comparison between Cabernet Sauvignon and Shiraz Cultivars from Australian Warm Climate.

The relationship between grape composition and subsequent red wine ester profile was examined. Cabernet Sauvignon and Shiraz, from the same Australian very warm climate vineyard, were harvested at two different stages of maturity and triplicate wines were vinified. Grape analyses focused on nitrogen and lipid composition by measuring 18 amino acids by HPLC-FLD, 3 polyunsaturated fatty acids, and 6 C6-compounds derived from lipid degradation by GC-MS. Twenty esters and four higher alcohols were analyzed in wines by HS-SPME-GC-MS. Concentrations of the ethyl esters of branched acids were significantly affected by grape maturity, but the variations were inconsistent between cultivars. Small relative variations were observed between wines for ethyl esters of fatty acids, whereas higher alcohol acetates displayed the most obvious differences with concentrations ranging from 1.5- to 26-fold higher in Shiraz than in Cabernet Sauvignon wines regardless of the grape maturity. Grape analyses revealed the variations of wine ester composition might be related to specific grape juice nitrogen composition and lipid metabolism. To the authors' knowledge the present study is the first to investigate varietal differences in the ester profiles of Shiraz and Cabernet Sauvignon wines made with grapes harvested at different maturity stages.

Gas chromatography-mass spectrometry method optimized using response surface modeling for the quantitation of fungal off-flavors in grapes and wine.

An optimized method for the quantitation of volatile compounds responsible for off-aromas, such as earthy odors, found in wine and grapes was developed. The method involved a fast and simple headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) for simultaneous determination of 2-isopropyl-3-methoxypyrazine, 2-isobutyl-3-methoxypyrazine, 3-octanone, fenchone, 1-octen-3-one, trans-2-octen-1-ol, fenchol, 1-octen-3-ol, 2-methylisoborneol, 2,4,6-trichloroanisole, geosmin, 2,4,6-tribromoanisole, and pentachloroanisole. The extraction of the temperature and time were optimized using response surface methodology in both wine base (WB) and grape base (GB). Low limits of detection (0.1-5 ng/L in WB and 0.05-1.6 in GB) and quantitation (0.3-17 in WB and 0.2-6.2 in GB) with good recoveries (83-131%) and repeatability [4.3-9.8% coefficient of variation (CV) in WB and 5.1-11.1% CV in GB] and reproducibility (3.6-10.2 in WB and 1.9-10.9 in GB) indicate that the method has excellent sensitivity and is suitable for the analysis of these off-flavor compounds in wine and grape juice samples.

Wine metabolomics: objective measures of sensory properties of semillon from GC-MS profiles.

The contribution of volatile aroma compounds to the overall composition and sensory perception of wine is well recognized. The classical targeted measurement of volatile compounds in wine using GC-MS is laborious and only a limited number of compounds can be quantified at any time. Application of an automated multivariate curve resolution technique to nontargeted GC-MS analysis of wine makes it possible to detect several hundred compounds within a single analytical run. Hunter Valley Semillon (HVS) is recognized as a world class wine with a range of styles. Subtle characters reliant upon the development of bottle maturation characteristics are a feature of highly esteemed HVS. In this investigation a metabolomic approach to wine analysis, using multivariate curve resolution techniques applied to GC-MS profiles coupled with full descriptive sensory analysis, was used to determine the objective composition of various styles of HVS. Over 250 GC-MS peaks were extracted from the wine profiles. Sensory scores were analyzed using PARAFAC prior to development of predictive models of sensory features from the extracted GC-MS peak table using PLS regression. Good predictive models of the sensorial attributes honey, toast, orange marmalade, and sweetness, the defining traits for HVS, could be determined from the extracted peak tables. Compound identification for these rated attributes indicated the importance of a range of ethyl esters, aliphatic alcohols and acids, ketones, aldehydes, furanic derivatives, and norisoprenoids in the development of HVS and styles. The development of automated metabolomic data analysis of GC-MS profiles of wines will assist in the development of wine styles for specific consumer segments and enhance understanding of production processes on the ultimate sensory profiles of the product.

Grapevine bunch rots: impacts on wine composition, quality, and potential procedures for the removal of wine faults.

Bunch rot of grape berries causes economic loss to grape and wine production worldwide. The organisms responsible are largely filamentous fungi, the most common of these being Botrytis cinerea (gray mold); however, there are a range of other fungi responsible for the rotting of grapes such as Aspergillus spp., Penicillium spp., and fungi found in subtropical climates (e.g., Colletotrichum spp. (ripe rot) and Greeneria uvicola (bitter rot)). A further group more commonly associated with diseases of the vegetative tissues of the vine can also infect grape berries (e.g., Botryosphaeriaceae, Phomopsis viticola ). The impact these fungi have on wine quality is poorly understood as are remedial practices in the winery to minimize wine faults. Compounds found in bunch rot affected grapes and wine are typically described as having mushroom, earthy odors and include geosmin, 2-methylisoborneol, 1-octen-3-ol, 2-octen-1-ol, fenchol, and fenchone. This review examines the current state of knowledge about bunch rot of grapes and how this plant disease complex affects wine chemistry. Current wine industry practices to minimize wine faults and gaps in our understanding of how grape bunch rot diseases affect wine production and quality are also identified.

Production technologies for reduced alcoholic wines.

The production and sale of alcohol-reduced wines, and the lowering of ethanol concentration in wines with alcohol levels greater than acceptable for a specific wine style, poses a number of technical and marketing challenges. Several engineering solutions and wine production strategies that focus upon pre- or postfermentation technologies have been described and patented for production of wines with lower ethanol concentrations than would naturally arise through normal fermentation and wine production techniques. However, consumer perception and acceptance of the sensory quality of wines manufactured by techniques that utilize thermal distillation for alcohol removal is generally unfavorable. This negative perception from consumers has focused attention on nonthermal production processes and the development or selection of specific yeast strains with downregulated or modified gene expression for alcohol production. The information presented in this review will allow winemakers to assess the relative technical merits of each of the technologies described and make decisions regarding implementation of novel winemaking techniques for reducing ethanol concentration in wine.

Sensory, chemical, and electronic tongue assessment of micro-oxygenated wines and oak chip maceration: assessing the commonality of analytical techniques.

Micro-oxygenation (MOX) was conducted in the presence and absence of oak chips at rates to mimic oxygen ingress during barrel maturation of red wine. Following MOX, wines were analyzed for chemical attributes pertaining to phenolic composition and assessed by a trained sensory panel. An electronic tongue (ET) was also used to assess the wines. Variations in chemical attributes were found to be mostly influenced by vintage, followed by oak chip maceration accounting for 48% and 16% of variation within the data set, respectively. MOX treatment accounted for 11% of variability within the physiochemical data set, with attributes pertaining to anthocyanin polymerization and levels of sulfur dioxide in the finished wine being most significantly influenced. A generalized Procrustes rotation and alignment of the chemical, electronic tongue, and sensory data sets followed by PLS1 regressions showed good prediction of the sensory characters oak, pencil shavings, stewed plum, vegetal, and spice over the range of sensory scores from the ET data; bitterness and astringency could also be predicted from the physicochemical data with good precision.