Showing papers in "Australian Journal of Grape and Wine Research in 2011"

General phenological model to characterise the timing of flowering and veraison of Vitis vinifera L.

Abstract: Background and Aims: Phenological models, which are based on responses of the plant to temperature, are useful tools to predict grapevine (Vitis vinifera L.) phenology in various climate conditions. This study aimed to develop a single process-based phenological model at the species level to predict two important stages of development for V. vinifera L.: flowering and veraison. Methods and Results: Three different phenological models were tested and the model that gave the best results was optimised for its parameters. The chosen model Spring Warming was found optimal with regard to the trade-off between parsimony of input parameters and efficiency. The base temperature (Tb) of 0°C calculated from the 60th day (t0) of the year (for the Northern hemisphere) was found to be the most optimal parameter set tested. This model henceforth referred to as the Grapevine Flowering Veraison model (GFV) was successfully validated at the varietal level using an independent dataset. Conclusions: A general phenological model, GFV, has been successfully developed to characterise the timing of flowering and veraison for the grapevine. Significance of the Study: The model is simple for the user, can be successfully applied to many varieties and can be used as an easy predictor of phenology for different varieties under climate change scenarios.

Variation in vine vigour, grape yield and vineyard soils and topography as indicators of variation in the chemical composition of grapes, wine and wine sensory attributes

Abstract: Background and Aims: Vineyard variability makes satisfaction of winemaker demands for uniform parcels of fruit that are suitable for particular product streams difficult. Indeed, it may not be possible to satisfy these demands without being able to adequately characterise differences between wines derived from different fruit parcels or different areas of the same vineyard, understanding how final wines are affected by management decisions implemented in the vineyard, and/or understanding the effects of variation in the vineyard's biophysical characteristics (e.g. soil, topography) on grape and wine composition. This work sought to identify and examine relationships between the chemical and sensory attributes of wines derived from different parts of the same block and the biophysical characteristics of these different vineyard areas. Methods and Results: Remote sensing of vine vigour, yield mapping and EM38 soil survey were used to identify zones of contrasting vineyard performance in a Cabernet Sauvignon vineyard in the Murray Valley region. Small-lot wines were made from fruit sourced from these zones. Both sensory and chemical analysis (solid phase microextraction-gas chromatography-mass spectrometry) of these wines demonstrated them to be different. Likewise, soil properties and indices of vine nutrition differed between the zones. Conclusions: This work suggests that it is possible for robust relationships to be established between specific (manageable) biophysical attributes of the place where grapes are grown and the sensory and chemical characteristics of the wines derived from them. It also supports the view that terroir is spatially variable at the within-vineyard scale. Significance of the Study: The work provides a foundation for further research aimed at establishing how specific sensory and/or chemical properties in wines might be modified through targeted management interventions in the vineyard.

Review: Winery wastewater quality and treatment options in Australia

Abstract: Commercial production of wine results in the generation of large volumes of wastewater, which typically contains large amounts of organic material and salts as a result of product loss and cleaning processes. The treatment and management of this waste stream is of significant concern, especially considering increasing environmental restrictions. There are numerous treatment options available for the management of wastewaters, which vary with respect to efficacy, cost and reliability. This review presents a summary of these treatment options, and describes the mechanism of each process, as well as the advantages and disadvantages of their use within the wine industry. The current knowledge of winery wastewater (WWW) composition and current and emerging management and/or treatment options are described, within an Australian context. Firstly WWW composition is discussed, and then both established and emerging physicochemical and biological treatment options reviewed, and options for disposal/re‐entry to the environment considered. Knowledge gaps and a way forward are presented in conclusion, and focus primarily on research in areas relating to WWW composition, and effects of WWW application on soil and plant health.

Effect of pre‐ and post‐veraison water deficit on proanthocyanidin and anthocyanin accumulation during Shiraz berry development

Abstract: Background and Aims: Water deficit is known to influence berry development as well as flavonoid metabolism. The aim of this study was to investigate the influence of pre- and post-veraison water stress on the proanthocyanidin and anthocyanin accumulation on berry samples selected at comparable physiological maturity, especially after veraison while avoiding sugar influence. Methods and Results: Three irrigation treatments were applied by a drip irrigation system on three rows of 30 vines from an experimental Shiraz vineyard. Pre-veraison water stress had no effect on total proanthocyanidin accumulation but increased accumulation of all anthocyanins except malvidin and p-coumaroylated derivatives, whereas post-veraison water stress enhanced the overall anthocyanin biosynthesis, particularly malvidin and p-coumaroylated derivatives. Conclusions: Pre- and post-veraison water stress affected the anthocyanin composition differently, suggesting a differential regulation of the genes involved in the last steps of anthocyanin biosynthesis pathway. Significance of the Study: The study identifies the effect of pre- and post-veraison water stress while avoiding sugar influence on anthocyanin accumulation which could be maximised since both stresses differently impacted hydroxylation and methylation of anthocyanins.

Projecting the impacts of climate change on the phenology of grapevine in a mountain area

Abstract: Background and Aims: The strong link between climate and grapevine phenology suggests a potentially stronger impact of climate change on viticulture in climate-limited areas, including mountain zones. The aim of this work was to evaluate the potential effects of climate change on grapevine phenology and viticultural suitability in a mountain region. Methods and Results: Climatic projections were applied to phenological models to determine the effect on stages of budburst, flowering and veraison for Vitis vinifera cv. Chardonnay. Calibration and validation of the models had been previously carried out in the same alpine region. The output of the general-circulation climatic model HadCM3, run with two different Intergovernmental Panel on Climate Change emission scenarios, was statistically downscaled to 10 locations in different agricultural sites in Trentino, Italian Alps, some of which are presently unfit for viticulture due to climatic limitations. Results yielded a trend of phenological advance, with interesting differences among phases and sites. Simulated advance was more pronounced at higher elevations, and larger for veraison than for spring phenophases. Conclusions: As a consequence of the considerable warming projected by future climate scenarios, some mountain sites at about 1000 m were expected to fall within areas climatically suitable for viticulture before the end of this century. Nevertheless, noticeable differences from present conditions are not expected within a short timescale. Significance of the Study: These projections, suggesting a more pronounced phenological response at higher elevations, may support the development of adaptation strategies aimed at maintaining the profitability of mountain viticulture even in times of global change.

Auxin treatment of pre-veraison grape (Vitis vinifera L.) berries both delays ripening and increases the synchronicity of sugar accumulation

Abstract: Background and Aims: Pre-veraison auxin treatments can delay grape berry ripening, but there is little information about their effects on berry development and wine composition. The aim of this study was to further investigate these effects and explore the practical implications of delaying ripening. Methods and Results: Treatment of pre-veraison Vitis vinifera L. cv. Shiraz berries with 1-naphthaleneacetic acid (NAA) significantly delayed ripening as measured by the accumulation of total soluble solids (TSS) and anthocyanins. The onset of the post-veraison phase of berry size increase was delayed in NAA-treated fruit, but these fruit were significantly larger than Control fruit at harvest. NAA-treatments significantly increased the synchronicity of berry sugar accumulation. GC-MS analysis of wine headspace volatiles showed significant, but largely small, differences in the concentration of 19 compounds. No significant difference in sensory properties was found between replicate small-scale wine lots made from Control and NAA-treated fruit. Conclusions: Auxin treatment delayed berry ripening, increased the synchronicity of sugar accumulation between berries, increased berry size and changed the levels of some volatile compounds, but did not affect wine sensory properties. Significance of the Study: We propose that NAA sprays might be used to delay grape berry ripening and increase the synchronicity of sugar accumulation, and therefore ripening, without deleterious effects on wine quality. This may be useful in controlling winery intake and fruit composition.

Non-destructive measurement of grapevine water potential using near infrared spectroscopy

Abstract: Background and Aims: Near infrared (NIR) spectroscopy techniques are not only used for a variety of physical and chemical analyses in the food industry, but also in remote sensing studies as tools to predict plant water status. In this study, NIR spectroscopy was evaluated as a method to estimate water potential of grapevines. Methods and Results: Cabernet Sauvignon, Chardonnay and Shiraz leaves were scanned using an Integrated Spectronic (300–1100 nm) or an ASD FieldSpec® 3 (Analytical Spectral Devices, Boulder, Colorado, USA) (350– 1850 nm) spectrophotometer and then measured to obtain midday leaf water potential using a pressure chamber. On the same shoot, the leaf adjacent the one used for midday leaf water potential measurement was used to measure midday stem water potential. Calibrations were built and NIR showed good prediction ability (standard error in cross validation (SECV) <0.24 MPa) for stem water potential for each of the three grapevine varieties. The best calibration was obtained for the prediction of stem water potential in Shiraz (R = 0.92 and a SECV = 0.09 MPa). Conclusion: Differences in the NIR spectra were related to the leaf surface from which the spectra were collected, and this had an effect on the accuracy of the calibration results for water potential. We demonstrated that NIR can be used as a simple and rapid method to detect grapevine water status. Significance of the Study: Grapevine water potential can be measured using NIR spectroscopy. The advantages of this new approach are speed and low cost of analysis. It may be possible for NIR to be used as a non-destructive, in-field tool for irrigation scheduling.

Vineyard variability in Marlborough, New Zealand: characterising variation in vineyard performance and options for the implementation of Precision Viticulture

Abstract: Background and Aims: Vineyards are variable. However, to date, no spatial analysis of vineyard variability has been conducted in New Zealand. We were interested to quantify variability in a Marlborough vineyard and to produce a spatial platform onto which modelled information on phenology and juice composition could be integrated. Methods and Results: A combination of remote and proximal sensing of vine vigour, direct measurement of trunk circumference, yield mapping and high resolution electromagnetic induction (EM38) soil survey was used to examine vineyard variability in a 5.9 ha Marlborough vineyard planted to Vitis vinifera L. cv. Sauvignon Blanc. Yield variation was little more than twofold, in spite of substantial variation in vine vigour which was associated with variation in the land (soil, topography) underlying the vineyard. Conclusions: A focus on tools that facilitate enumeration of variation in vine vigour may offer the greatest value to Marlborough practitioners interested in adopting Precision Viticulture approaches to grapegrowing and winemaking. EM38 soil survey appeared to be useful for describing vineyard soil variation, but because the soils that predominate over the alluvial Wairau Plains in Marlborough are shallow and stony, very low values of apparent electrical conductivity (ECa) over a narrow range were observed. However, ECa was closely correlated with trunk circumference, an index of vine vigour. In contrast to Australian studies, neither ECa, plant cell density (derived from remotely sensed imagery) nor trunk circumference were good predictors of grapevine yield. It is hypothesised that this is largely a reflection of differences in vine training systems (hand cane pruning in Marlborough vs mechanical pruning in Australia) and the greater degree of selection of buds when vines are hand pruned. Significance of the Study: This is the first such study conducted in New Zealand and provides results that contrast with similar studies conducted in Australia. Nevertheless, the maps produced are expected to provide a valuable platform for a follow-up study aimed at understanding spatial variation in vine phenology and juice composition. The study also highlighted the power of kriging as a means of interpolating useful vineyard maps from relatively sparse, unevenly distributed sampling data.

Assessing desirable levels of sensory properties in Sauvignon Blanc wines – consumer preferences and contribution of key aroma compounds

Abstract: Background and Aims: This study aimed to investigate the sensory properties and aroma compounds responsible for driving consumer preference of Sauvignon Blanc wines. Methods and Results: Three thiols, including their respective enantiomers, a methoxypyrazine and a combination of esters were added singly and in combinations to a neutral white wine at realistic concentrations to mimic Sauvignon Blanc wines. A sensory descriptive analysis of 21 samples was conducted. While each thiol contributed to tropical and cat urine/sweaty attributes, 3-mercaptohexyl acetate (3MHA) was of particular importance. The ‘green’ characteristics were primarily related to methoxypyrazine, but thiols were also found to contribute to a cooked green vegetal attribute. The aroma and flavour of the methoxypyrazine dominated the sensory properties of other components. The thiol S-enantiomers gave higher cooked green vegetal or cat urine/sweaty than their R-counterparts. Six combinations and the base wine were evaluated for liking by 150 consumers. One cluster of consumers (31%) preferred wines with higher tropical and confectionary aroma; a second cluster (43%) preferred wines with ‘green’ attributes; and the final cluster's liking was positively related to solvent and ‘green’ attributes, and negatively to tropical and cat urine/sweaty. Conclusions: There were strong and varied interactive effects among the compounds studied. A sizeable proportion of consumers tested preferred the samples with ‘green’ attributes, with a minority preferring the ‘fruit’ aromas. Significance of the Study: This study has shown clear definition of sensory attributes resulting from aroma compounds important to Sauvignon Blanc wines, their interactions and their effects on consumer preference.

Vineyard variability in Marlborough, New Zealand: characterising spatial and temporal changes in fruit composition and juice quality in the vineyard

Abstract: Background and Aims: Previous work has demonstrated that vineyards are spatially variable and that this variability can be understood in terms of the underlying characteristics of the land (soils, topography) supporting the vineyard. Selectively harvesting blocks in response to such variability may be highly profitable. While it has also been shown that crop maturation is spatially variable, there may also be temporal variations in the rate of maturation. Integrating knowledge of how spatial variation in fruit composition may be moderated in time has not previously been attempted and is the key objective in this work. Methods and Results: We used a proximal sensor to map vine vigour at high spatial resolution in a 5.9-ha Marlborough vineyard planted with Sauvignon Blanc. Vigour measurements were also related to fruit-soluble solids (SS), titratable acidity (TA) and pH – key indices of crop maturity. Knowledge of crop phenology and maturation was used to predict how these indices changed with time. The pooled opinions of over 50 Marlborough winemakers on the optimum juice SS, pH and TA at harvest to produce a ‘typical Marlborough Sauvignon Blanc’ were used to develop a juice index (JI), which in turn was mapped in space and time at the study site. The JI showed marked spatial and temporal variation. Conclusions: In addition to being spatially variable, grape quality in vineyards also changed with time. Thus, the optimisation of decisions about harvest timing requires knowledge of spatial variability. Conversely, strategies such as selective harvesting cannot be properly optimized without knowledge of crop phenology, the maturation of fruit and their implications for fruit quality – which are all also spatially variable. In this study, we have shown that, by integrating knowledge of crop phenology with an understanding of vineyard variability and winemaker objectives through the construction of a JI, it is possible for the optimum harvest decision to be made such that fruit destined for a particular end use are harvested at the right time and from the right place. Significance of the Study: This is the first study in which knowledge of both spatial and temporal vineyard variation has been integrated. It demonstrates that in order to be optimal, strategies such as selective harvesting need to incorporate knowledge of crop phenology rather than rely on knowledge of spatial variation alone.

Climate shifts in south-eastern Australia: early maturity of Chardonnay, Shiraz and Cabernet Sauvignon is associated with early onset rather than faster ripening

Abstract: Background and Aim: Early maturity of grape crops associated with recent warming is well documented but poorly understood. Here, we ask the question: is early maturity associated with early onset of ripening or with increased rate of sugar accumulation? Methods and Results: We used records of grape juice total soluble solids (TSS) for Chardonnay, Shiraz and Cabernet Sauvignon collected in commercial vineyards between 1995 and 2009. The combination of 15 vintages and three climatic regions yielded a range of average seasonal temperature between 15.5 and 20.5°C. Using boundary functions of TTS versus time, we derived the onset and rate of increase in TSS, and the time of maturity set at 12 °Be for comparative purposes. Pooled across varieties, the rate of change in maturity was −9.8 ± 0.94°C/d. Shifts in onset accounted for 86% of the variation in time of maturity and the rate of ripening for the remaining variation. Conclusion: Early maturity associated with higher temperature (and related factors including higher radiation and higher vapour pressure deficit) is primarily driven by early onset of ripening under a wide range of production systems in south-eastern Australia. Significance of the Study: Viticultural practices aiming at delaying maturity to counteract the effect of high temperature, high radiation and high vapour pressure deficit are more likely to be successful if they target the onset of ripening.

Stomatal density of grapevine leaves (Vitis vinifera L.) responds to soil temperature and atmospheric carbon dioxide

Abstract: Background and Aims: Leaf stomatal density, i.e. number of stomata per unit area of leaf, is a primary determinant of the carbon and water relations of plants. However, little is known about the plasticity of grapevine stomatal density during leaf formation in response to environmental factors. In this study, we determined responses in stomatal density to soil temperature and atmospheric carbon dioxide during leaf development following dormancy to gain further understanding of grapevine carbon and water relations, and adaptation to climate change. Methods and Results: Using potted plants of Vitis vinifera (L.) cv. Chardonnay, we found that a period of soil warming from budbreak reduced stomatal density of concurrently formed leaves, whereas CO2 depletion increased it. Furthermore, stomatal density of concurrently formed leaves was closely and inversely correlated with starch concentration in roots and trunks. Conclusion: We conclude that the stomatal density of grapevine leaves varies greatly in response to soil temperature and atmospheric CO2 concentration. Significance of the Study: This is the first study to show that soil temperature influences stomatal density of plants. It also confirms that stomatal density of grapevines, like many other plants, responds inversely to atmospheric CO2 concentration. Our findings demonstrate that stomatal density must be accounted for in any attempt to predict grapevine adaptation to climate change, and attendant impacts on CO2 assimilation and water use efficiency in viticulture. More fundamentally, they indicate that the carbohydrate reserve status of perennial, deciduous plant species may be an important endogenous determinant of stomatal density.

Use of unripe grapes harvested during cluster thinning as a method for reducing alcohol content and pH of wine

Abstract: Background and Aims: Deep red full-bodied wines can only be obtained from grapes with complete phenolic maturity, which frequently produce wines with high pH and alcohol content The present study focuses on a new procedure for simultaneously reducing pH and ethanol content Methods and Results: Grapes from cluster thinning were used to produce a very acidic low-alcohol wine The wine was treated with high doses of charcoal and bentonite This odourless and colourless wine was used to reduce pH and ethanol content of wine produced from grapes, which had reached complete phenolic maturity The anthocyanin and proanthocyanidin concentrations, the mean degree of polymerisation and the monomeric composition of proanthocyanidin of reduced-alcohol wines were similar to those of their corresponding controls Since the pH was lower, the colour of the reduced-alcohol wines was more intense No significant differences were found between reduced-alcohol wines and their controls by triangle sensory tests using dark glasses for two of the three studied cultivars Conclusion: The procedure described allowed production of wines with reduced alcohol content and pH, while retaining similar phenolic content and sensory properties Significance of the Study: The proposed procedure is easy to apply, does not require specific equipment and offers a means of addressing the problem of wines developing high ethanol and low pH as a result of over-ripening of grapes

Contribution of cysteine and glutathione conjugates to the formation of the volatile thiols 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA) during fermentation by Saccharomyces cerevisiae

Abstract: Background and Aims: 3-Mercaptohexan-1-ol (3MH) and its ester 3-mercaptohexyl acetate (3MHA) are potent aromatic thiols that substantially contribute to varietal wine aroma. During fermentation, non-volatile 3MH conjugates are converted by yeast to volatile 3MH and 3MHA. Two types of 3MH conjugates have been identified, S-3-(hexan-1-ol)-L-cysteine (Cys-3MH) and S-3-(hexan-1-ol)-glutathione (GSH-3MH). Yeast-driven formation of 3MH from these precursors has been previously demonstrated, while the relationship between 3MHA and GSH-3MH remains to be established. This paper aims to investigate yeast conversion of GSH-3MH to 3MH and 3MHA, and to assess the relative contribution of each individual conjugate to the 3MH/3MHA pool of finished wines. Methods and Results: Fermentation experiments were carried out in model grape juice containing Cys-3MH and GSH-3MH. We found 3MH formation from GSH-3MH to be significantly less efficient than that of Cys-3MH. Conversely, esterification of 3MH to 3MHA was higher when 3MH was formed from GSH-3MH. Additional in vitro assays for measuring enzyme cleavage activity suggest the involvement of a different mechanism in 3MH conversion for the two precursors. Conclusions: These results indicate that although both 3MH conjugates can be converted by yeast, the type of precursor affects the rate of formation of 3MH and 3MHA during fermentation. Significance of the Study: Management of the pool of aromatic thiols during fermentation can depend on relative proportions of different 3MH conjugates.

New chitosan formulation prevents grapevine powdery mildew infection and improves polyphenol content and free radical scavenging activity of grape and wine

Abstract: Background and Aims: Chitosan, a chitin deacetylated derivative, is a biopolymer able to elicit the plant defence machinery against a variety of pathogens. In crop protection, it is successfully employed for its low toxicity, mainly against virus diseases. In this study, the efficacy of a new chitosan formulation (Kendal Cops® (Kc)) was evaluated in grapevine against powdery mildew infection. Total polyphenol (TP) content and antiradical power of different grape tissues and of experimental wines produced from treated grapes were also assessed. Methods and Results: Field treatments with different Kc dilutions or with Kc alternated or mixed with fungicides, or with fungicides alone (penconazole and methyldinocap) were carried out in an experimental vineyard of the cv. Montepulciano d’Abruzzo. Kc was effective in controlling powdery mildew, particularly at the concentration of 0.1%, even under high disease pressure conditions. In this case, disease severity was 2.39% in treated grapes, compared with 87.5 and 0.92% in untreated and conventional fungicide-treated grapevines, respectively. TP content, measured by Folin‐Ciocalteau colorimetric assay, was significantly higher in all Kc-treated grape tissues, compared with both untreated controls and fungicide-treated grapes. A similar trend was reported with regard to the antioxidant activity, assessed by 2,2-diphenyl-1-pycryl hydrazyl free radical scavenging test. Analysis of wines showed that both TPs and antiradical power were significantly higher in wines made from Kc-treated grapes compared with fungicide-treated ones. Conclusions: Kc not only protected grapevine from powdery mildew but also improved TP content and antioxidant activity in both grapes and wine. Significance of the Study: The possibility of using plant defence inducers in crop protection deserves particular attention because of their low environmental impact and of their ability to improve some quality traits of plant foodstuffs. Furthermore, in contrast to fungicides, they hardly select resistant pathogen strains and do not incur fitness costs for the plant.

Protein evolution during the early stages of white winemaking and its relations with wine stability

Abstract: Background and Aims: Grape proteins are responsible for the appearance of haziness in white wines during storage after bottling. However, only a few studies have approached the analysis of the fate of must proteins throughout the alcoholic fermentation. This study aimed to systematically investigate the daily variations in protein type and content during the fermentation in order to understand its influence on hazing potential and to attain some basic information to improve the practical management of grape proteins involved in the hazing of white wines. Methods and Results: The evolution of total soluble protein and individual protein fractions was studied in samples taken before, during and after alcoholic fermentation of a white grape must. The results were then related to variations in protein instability as measured by the heat test. Both the quantity of soluble protein and the protein instability increased during fermentation and then decreased after 1-month storage of the wine. Protein composition did not vary during fermentation as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and anion exchange chromatography (AEC). However, variations in the relative proportions of the six protein fractions obtainable by AEC were noted in the different samples. The contribution of each AEC protein fraction to wine instability was determined by considering both the intrinsic instability and the relative quantity of each of the individual protein fractions in the wine. It was demonstrated that the grape thaumatin-like protein VVTL1, as identified by mass spectrometry, showed the largest increase during fermentation and accounted for almost 40% of the heat-induced haze of the final wine. Moreover, the decreased protein instability noted after one month storage of the wine could be attributed to the stabilizing effect of polysaccharides released by the yeast cells. Conclusions: The quantity and relative proportion of soluble proteins vary during and after the alcoholic fermentation, as does their heat instability in wine. Grape VVTL1, constituting a large proportion of the total proteins in wine, seems to play a major role in protein haze formation. The release of yeast polysaccharides is related to an increased heat stability of total wine protein, despite the increase in the relative proportion of their most unstable component VVTL1. Therefore, the hazing potential of a white wine seems to be affected by variations in the relative proportions of its macromolecular components occurring in the early stages of winemaking. Significance of the Study: This study addressed for the first time the issue of the protein changing during the fermentation of white wine. The results obtained here offer useful information to aid understanding of the contribution of individual proteins to white wine instability, which can be applied for the improvement of the winemaking process. Abbreviations AEC anion-exchange chromatography; KDS potassium dodecyl sulfate; MS mass spectrometry; MW molecular weight, PAS periodic acid-Schiff stain, PR-proteins pathogenesis-related proteins, RT retention time, SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis, TL thaumatin-like, VVTL1 Vitis vinifera thaumatin-like protein

The effect of winemaking techniques on the intensity of smoke taint in wine

Abstract: Background and Aims: The chemical composition and sensory properties of smoke-affected grapes and wine has been the subject of several recent studies. However, while this research has addressed early knowledge gaps surrounding the effect of smoke on grapes and wine, to date, no practical solutions that mitigate the incidence or severity of smoke taint have been reported. The current project therefore aimed to identify winery processing methods that minimise the sensory impact of smoke taint in wine. Methods and Results: Different winemaking techniques were used to process smoke-affected grapes, i.e. cold maceration, the use of different yeast strains for primary fermentation and the use of oak and tannin additives. The extent of smoke taint in the resulting wines was determined by quantification of volatile phenols using GC-MS, followed by descriptive sensory analysis. Conclusions: Applied winemaking practices showed significant impacts on reducing the negative implications of smoke exposure on the chemical composition and sensory properties of wines. Winery processing methods that reduced skin contact time enhanced fruit character, produced wines with reduced ‘smoke’ aromas and flavours and less apparent taint. Selected yeast strains can be used as a tool for altering smoke-related aromas, flavours, colour and chemical composition of wines. The addition of oak chips and tannin enhanced the complexity of wines thereby reducing the perception of smoke-related attributes. Significance of the Study: These findings will enable winemakers to make more informed decisions when processing smoke-affected grapes, in order to minimise the severity of smoke taint perception in resulting wine.

Characterisation and evolution of grape polyphenol profiles of Vitis vinifera L. cv. Tannat during ripening and vinification

Abstract: Background and Aims: Changes in different polyphenol families during grape ripening and vinification were determined in Tannat grapes. This was done to establish a polyphenol profile for Tannat grapes during ripening and for young wines. Methods and Results: We demonstrated, by high-performance liquid chromatography with diode array detection and mass spectrometry (HPLC-DAD-MS) analysis, that the content of flavan-3-ols in Tannat seeds was higher than that reported for a large number of other grape varieties analysed. Forty per cent of the total flavan-3-ols in seeds were galloylated compounds, whereas the flavan-3-ol profile in skins was characterised by the absence of galloylated forms. Prodelphinidins in skins ranged between 30 and 35% with very low values for epigallocatechin. Epicatechin gallate was not detected in Tannat wine and galloylated forms represented a low percentage of total flavan-3-ols. Tannat grapes had very high concentrations of anthocyanins in skins with levels increasing during ripening. Eleven phenolic acids were identified in Tannat grape skins and wines, but only gallic and protocatechuic acids were found in the seeds. Conclusions: Tannat wines were shown to have one of the highest levels of phenolic compounds reported for vinifera grape varieties. The profiles for different polyphenol families present in Tannat grapes (skins and seeds) and wines were determined. Significance of the Study: The results presented will help to better understand the phenolic winemaking potential of this variety and its functional properties within food chemistry.

Effect of mechanical leaf removal and its timing on flavan‐3‐ol composition and concentrations in Vitis vinifera L. cv. Pinot Noir wine

Abstract: Background and Aims: Mechanical leaf removal of Pinot Noir vines was carried out in a commercial vineyard in Waipara, New Zealand in the 2007–2008 and 2008–2009 growing seasons. The aim was to investigate the effects of different timings on flavan-3-ol composition and concentrations in Pinot Noir wine produced from the treatments. Methods and Results: Treatments were leaf removal from the fruiting zone 7 days after flowering, 30 days after flowering and at veraison (by visual assessment), and no leaf removal (control). Proanthocyanidin concentrations in berries by the methylcellulose precipitation assay at harvest showed no difference between treatments, although the LR7 wine had the highest methylcellulose precipitable tannin concentration in 2007–2008, the LR30 wine had the highest concentration in 2008–2009 and the NLR wine had the lowest in both years; the 2009 wines had increased concentrations compared to 2008. Greatest concentrations of flavan-3-ol monomers by reverse phase high performance liquid chromatography were found in LR7 wines. An increase in the ratio of 2,3-trans to 2,3-cis flavan-3-ols was observed with earlier leaf removal. The mean degree of polymerisation (mDP) by acid catalysis in the presence of phloroglucinol showed no statistical difference between wines. Conclusions: Early timing of mechanical leaf removal increases proanthocyanidin concentration, but has no influence on the mDP. Increased severity of defoliation and/or higher alcohol levels in the 2008–2009 growing season were responsible for the differences in total tannin concentration compared to the previous year. Significance of the Study: The timing of mechanical leaf removal can influence wine flavan-3-ol concentrations.

Guaiacol and 4‐methylguaiacol accumulate in wines made from smoke‐affected fruit because of hydrolysis of their conjugates

Abstract: Background and Aims: Taint in smoke-exposed grapes have been associated with elevated levels of guaiacol and 4-methylguaiacol. Previous research has reported guaiacol and 4-methylguaiacol in both fruits and wines. In some cases, these compounds were not detected, or were detected at low levels in the fruit while high levels were subsequently identified during or after winemaking. Later research indicated that this was due to the presence of glycosidic conjugates. Here we report a method for the routine analysis of guaiacol and 4-methylguaiacol released after acid hydrolysis of glycoside precursors. Methods and Results: Chardonnay, Merlot, Shiraz, Sangiovese and Cabernet Sauvignon fruits were collected following bushfire events in 2006–2007 in the King Valley wine region of NE Victoria, Australia. Gas chromatography-mass spectrometry (GC-MS) was used to detect free guaiacol and 4-methylguaiacol in both fruits and wines. Low levels of free and bound forms were present in fruit not exposed to smoke. Substantial levels of free guaiacol and 4-methylguaiacol were detected in the wines made from the smoke-affected fruits. These compounds increased during bottle storage. Acid hydrolysis of wines and berries resulted in a several-fold increase in free guaiacol and 4-methylguaiacol. Conclusions: The validated GC-MS method is suitable for monitoring free and glycosidically bound guaiacol and 4-methylguaiacol after acid hydrolysis in both fruits and wines. Acid hydrolysis of wines provided evidence that bound volatiles, most probably glycosidically, act as reserve for guaiacol and 4-methylguaiacol, which are released during ageing of wines. Significance of the Study: This is the first study published in a refereed journal to demonstrate that smoke taint-associated volatiles increase during ageing of wine and bound forms of guaiacol and 4-methylguaiacol represent an aroma reserve for smoke taint in ageing/bottled wines.

Selective harvesting is a feasible and profitable strategy even when grape and wine production is geared towards large fermentation volumes

Abstract: Background and Aims: Previous work has identified the potential for enhancing the profitability of both grapegrowing and winemaking through the implementation of selective harvesting. However, there has been a perception that such strategies may not be feasible when winery infrastructure is geared to large production volumes, such as is commonly the case in Australia's warm irrigated regions. This work sought to examine the merits of this perception. Methods and Results: The tools of Precision Viticulture were used to identify zones of similar vineyard performance in two Cabernet Sauvignon vineyards in the Murray Valley region of Victoria such that sufficient quantities of fruit were available for commercial scale vinification into different product lines. Wines from these zones were also made in small lots. Sensory analysis demonstrated that wines derived from like zones were indeed similar, whilst those from contrasting zones were discernibly different. A partial gross margin analysis strongly suggested that selective harvesting should be highly profitable. Conclusions: If market opportunity warrants it, selective harvesting of fruit into different product streams is a feasible and profitable strategy even when production is geared to large volumes. Significance of the Study: The work demonstrates that selective harvesting can be profitably applied in situations where production is geared to large fermentation volumes. It therefore provides a counter to the view that Precision Viticulture offers opportunities only to small (boutique) producers or to large, well-resourced companies with a flexible winery infrastructure.

On-the-go sensing of grape berry anthocyanins during commercial harvest: development and prospects

Abstract: Background and Aims: The development and adoption of Precision Viticulture approaches to grape and wine production have been hindered by the lack of a commercially available sensor for on-the-go sensing of fruit quality during harvest. In this work, we sought to deploy the Multiplex®, a fluorescence-based non-contact hand-held optical sensor on a harvester, for on-the-go sensing of berry anthocyanins during the South Australian vintage of 2010. Methods and Results: Measurements made of anthocyanin concentrations in the laboratory using the Multiplex showed high correlation (R2 > 0.9) with those made on the same grapes using the standard spectrophotogrametric method. When used in hand-held mode in the field, data collected using Multiplex demonstrated a similar spatial structure to that observed in other data layers (remotely sensed vigour, yield, elevation). Similarly, when deployed on a harvester as an on-the-go sensor, data obtained using Multiplex exhibited the expected spatial structure. Conclusions: Meaningful measurement of grape berry anthocyanins on-the-go during harvest is feasible using Multiplex. Significance of the Study: This is the first time that berry colour has been sensed on-the-go during harvest. The work therefore paves the way for a greater focus on attributes of fruit quality in the delineation of vineyard management zones and implementation of Precision Viticulture.

Amelioration of smoke taint in wine by reverse osmosis and solid phase adsorption

Abstract: Background and Aims: Wines made from grapes harvested from vineyards exposed to bushfire smoke can exhibit objectionable ‘smoky’, ‘cold ash’, ‘medicinal’ and ‘ashy’ aroma and flavour characters. This study evaluated a combined reverse osmosis and solid phase adsorption process as a potential amelioration method for the treatment of smoke-tainted wines. Methods and Results: Smoke-tainted wines were treated using either pilot or commercial scale reverse osmosis systems and the chemical composition and sensory properties of wine compared before and after treatment. The concentrations of smoke-derived volatile phenols, including marker compounds, guaiacol and 4-methylguaiacol, decreased significantly with treatment. As a consequence, diminished smoke-related sensory attributes enabled treated wines to be readily differentiated from untreated wines. However, the taint was found to slowly return with time, likely because of hydrolysis of glycoconjugate precursors, which were not removed during the treatment process. Conclusions: Reverse osmosis and solid phase adsorption reduced the concentration of smoked-derived volatile phenols and improved the sensory attributes of smoke-tainted wines. Significance of the Study: This is the first study to evaluate the amelioration of smoke taint in wine using reverse osmosis and solid phase adsorption.

Effect of smoke application to field‐grown Merlot grapevines at key phenological growth stages on wine sensory and chemical properties

Abstract: Background and Aims: Smoke exposure of grapevines and development of smoke taint in wine are issues of increasing incidence and severity. There is limited understanding of the effect of phenological stage at the time of smoke exposure on taint development. The aim of this study was to demonstrate the variation in smoke uptake and taint development between and within seasons. Methods and Results: Smoke was applied to field-grown Merlot grapevines at 12 stages of vine development over three growing seasons. Key periods of vine sensitivity to smoke taint in wine were (i) from shoots at 10 cm to full bloom (low levels of smoke taint); (ii) from berries at pea size to the onset of veraison (variable levels of smoke taint); and (iii) between 7 days post-veraison and harvest (high levels of smoke taint). Conclusions: The severity of taint in wine varied depending on the phenological timing of grapevine smoke exposure. Taint was elevated when exposure occurred between 7 days post-veraison and harvest. The carry-over of smoke constituents the following season was not detectable in wine but yields were reduced. Significance of the Study: This is the first study to demonstrate the timing of smoke exposure to critically affect wine chemical and sensory characters. These effects were consistent and reproducible over three seasons.

Allometric and biochemical responses of grapevines subjected to drought and enhanced ultraviolet‐B radiation

Abstract: Background and Aims: The aim of this study was to evaluate differences in adaptive responses in grapevines (Vitis vinifera L. cv Soultanina) exposed to either drought, enhanced ultraviolet-B (UV-B) radiation or the combination of the two environmental stresses. Methods and Results: Results indicated pronounced effects on allometric parameters in plants exposed to the enhanced UV-B radiation. The combined application of drought and enhanced UV-B radiation considerably affected shoot growth rate and leaf dry weight. Guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), superoxide dismutase (SOD, 1.15.1.1) and catalase (CAT, 1.11.1.6) activities increased significantly in the enhanced UV-B radiation treatment. Drought resulted in a significant increase in proline concentration, while the exposure of plants to enhanced UV-B radiation resulted in the production of UV-B absorbing compounds (UVabs). Conclusions: Under drought conditions proline accumulation seemed to be the main mechanism of adaptation contributing to plant's antioxidant defence. On the other hand, under enhanced UV-B radiation, the accumulation of the UV-B absorbing compounds and the increase in antioxidant enzymes activities constitute the main mechanisms of grapevine adaptation. Significance of the Study: The data obtained indicate the occurrence of two different mechanisms of adaptation in response to the stressor applied. Furthermore, the patterns of proline and UVabs concentration changes under stress conditions suggest that the biosynthesis of these two compounds might follow competing metabolic pathways.

The relationship between sensory attributes and wine composition for Australian Cabernet Sauvignon wines

Abstract: Background and Aims: The study explores the diversity in sensory characteristics of Cabernet Sauvignon wines from Australia and analyses the relationship between sensory attributes and wine composition. Methods and Results: Descriptive sensory analysis was conducted by eighteen panelists who rated the intensity of 16 aroma attributes and four taste attributes. Sensory results indicated that 15 of the 20 sensory attributes assessed were significantly different among the wines assessed. The primary differentiation was between wines that were fruity and those that exhibited vegetal and herbaceous characteristics. A recently developed analytical method (headspace solid-phase microextraction comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry) was used to analyse over 350 volatile compounds in the wines assessed. Other measures of the major non-volatile components including ethanol, phenolics, acids and sugars were also determined. Compositional results were used to predict each sensory attribute using partial least squares regression and showed that each sensory attribute could be well explained by the compositional results. Conclusions: The results of this study further demonstrate that the sensory perception of wine is complex and involves the interaction of both volatile and non-volatile components. The use of a recently developed analytical technique allows the researcher greater capacity to explore complex relationships between wine sensory characteristics and wine composition. Significance of the Study: The study increases the understanding of commercial wine composition and identifies a number of candidate components that are correlated with sensory attributes of Cabernet Sauvignon wines from Australia.

Comparison of methods for the analysis of smoke related phenols and their conjugates in grapes and wine

Abstract: Background and Aims: Australian grape growers and winemakers have typically relied on guaiacol and 4-methylguaiacol measurements to determine smoke exposure of grapes following bushfires or prescribed burns However, the guaiacol and 4-methylguaiacol content of grapes does not always correlate with the extent of taint in resultant wines This study compared several methods for the analysis of smoke related phenols and their conjugates in grapes and wine, to determine their capacity as diagnostic assays for smoke exposure Methods and Results: Smoke-affected grapes were sourced from commercial vineyards exposed to bushfire smoke and from experimental field trials involving the application of smoke to grapevines, and small-scale wines were made from a number of these samples Several analytical methods were applied to grapes and wine to determine the concentration of smoke related phenols and their conjugates Strong correlations were observed between the glycoconjugate content of smoke-affected grapes and the concentration of guaiacol and 4-methylguaiacol released following acid hydrolysis of juice Conclusions: Where smoke-affected grapes contain low or non-detectable levels of guaiacol and 4-methylguaiacol, analytical methods that quantify their glycoconjugate forms (either directly or indirectly) provide a better indication of the extent of smoke exposure Significance of the Study: This is the first study to compare different methods for assessing smoke exposure in grapes and wine, through analysis of free and bound guaiacol and 4-methylguaiacol These methods will allow grape growers and winemakers to more reliably assess smoke exposure of grapes, enabling better informed decisions to be made with regards to harvesting and processing smoke-affected grapes

The effect of bentonite fining at different stages of white winemaking on protein stability

Abstract: Background and Aims: Bentonite fining to remove protein is the most widely used treatment to prevent protein haze in white wines. Bentonite can be added at different stages during winemaking. This study aimed to determine the best time to add bentonite. Methods and Results: Unstable juices were vinified after bentonite fining of juice, or with bentonite added either early or late in fermentation. Different addition rates of bentonite were used and bentonite was either added in one or two additions. Fermentation rates were observed and protein stability and bentonite fining rates of the resultant wines were determined. Conclusions: Adding bentonite during fermentation or fining finished wines was the most efficient option in terms of amounts of bentonite required. Fermenting with bentonite present also may increase fermentation rates. Significance of the Study: Using the least bentonite necessary for heat stability is important for winemakers for quality, cost and environmental reasons. This study describes ways in which bentonite addition rates can be minimised.

Rapid and non‐destructive method to assess in the vineyard grape berry anthocyanins under different seasonal and water conditions*

Abstract: Background and Aims: Monitoring of anthocyanins (Anth) in winegrape (Vitis vinifera L.) is fundamental for the production of top-quality red wines. This work was aimed at testing a new fluorescence-based sensor for Anth detection in the vineyard. Significance of the Study: The present study showed a new important innovative technology for viticulture. The sensor evaluation of the large spatial and temporal heterogeneity in Anth accumulation can be useful as support parameter in the harvest date decision or for vineyard zoning of phenolic maturity. Methods and Results: Anth in grape (cv. Aleatico) bunches attached to the vine were monitored non-destructively in the field using a fluorescence-based sensor during the 2008 and 2009 seasons and under different water regimes. The ANTHRG index = log(far-red-fluorescenceR/far-red-fluorescenceG), with fluorescence signals excited with red (R) and green (G) light, was inversely correlated through an exponential function (r2 = 0.875) to the Anth concentration derived from the HPLC analysis of berry skin extracts. ANTHRG was effective in detecting the earlier ripening process in 2009 with respect to 2008 and differences in the Anth accumulation between seasons and in relation to different water regimes. Water deficit imposed in 2009 enhanced Anth concentration in berries because of a reduction in berry size but also an increase of Anth biosynthesis. This effect was observed by both destructive and ANTHRG non-destructive measurements. Conclusions: Our results show that the employed fluorescence sensor represents a reliable, rapid and non-invasive tool for monitoring and determining Anth accumulation in situ.

Sensory properties of premium Spanish red wines and their implication in wine quality perception

Abstract: Background and Aims: Little is known about the link between quality and the sensory space of premium commercial Spanish red wines. The major aims of the present study were to define the sensory space of these wines and determine the implication of their sensory properties (aroma and in-mouth attributes) in the quality perception of wine professionals. Methods and Results: Evaluation of wine quality was first studied by a categorisation task. Then, sensory descriptive analysis based on citation frequencies for aroma attributes and conventional intensity scores for taste and mouth-feel properties was performed on individual samples. The general sensory quality was highly positively correlated to astringency and, to a lesser extent, to acidity as well as to fruity, spicy and roasted/woody attributes, and especially highly negatively correlated to aromatic attributes belonging to the animal family. Conclusions: Categorisation tasks based on quality perception coupled to sensory analysis based on citation frequencies for aroma properties and on classical descriptive analysis for taste and mouth-feel properties could be suitable tools to finely determine sensory quality. The results highlight the importance of in-mouth properties, especially of astringency and acidity, in general quality as well as the relevance of the aromatic profile. Significance of the Study: This study increases the information on the sensory properties of premium Spanish red wines and the implication of concrete sensory attributes in sensory quality perception. This work provides winemakers information to be considered when elaborating high quality red wines.