Rotundone Concentration Research Articles

Use of auxin to delay ripening: sensory and biochemical evaluation of Cabernet Sauvignon and Shiraz

Background and Aims Climate change is prompting earlier grape ripening and harvest compression causing quality and logistical problems for growers and winemakers. Application of 1-naphthalene acetic acid (NAA) offers a management tool to delay ripening and expand the harvest window. This study extends previous findings about the effect of NAA on Shiraz fruit and wine composition and provides the first analysis of NAA-induced ripening delay of Cabernet Sauvignon. Methods and Results Pre-veraison NAA treatment of Shiraz and Cabernet Sauvignon grapes delayed harvest maturity by 3–4 weeks. Modification of nutrient accumulation was minor, and wines made from NAA and Control fruit displayed no significant variation in basic chemical properties. The concentration of methoxypyrazine in NAA-treated Cabernet Sauvignon grapes was unaffected, whereas NAA-treated Shiraz fruit and wine contained an elevated concentration of rotundone. The overall difference in wine volatile profiles between NAA and Control was small for both cultivars, reflected by Rate-All-That-Apply assessments that found no (Cabernet Sauvignon) or few (Shiraz) sensory attributes distinguishing the wines. Conclusions Application of NAA delays winegrape ripening with small, cultivar-dependent effects on grape and wine composition, that are unlikely to negatively affect wine sensory perception. Significance of the Study This work further establishes NAA as a ripening-delay agent that could be used commercially to delay grape maturation and decompress harvest while preserving berry integrity and wine typicity.

Effect of some winemaking factors on rotundone levels of Pelaverga di Verduno wines

Pelaverga di Verduno Protected Designation of Origin is a red wine obtained from Pelaverga piccolo, an autochthonous grape variety grown in Piedmont. This wine is characterized by a light colour and a unique, intense spicy aroma. The analysis of this wine detected a significant concentration of rotundone (approximately 40 ng L−1), which is known to impart a distinctive pepper note and has a very low olfactory threshold (16 ng L−1 in wine). The measured concentrations, well above the perception threshold, could link rotundone directly to the spicy notes highlighted by the sensorial analysis of Pelaverga wines. The impact of certain oenological factors on the concentration of this compound in wine was therefore assessed, showing that moderate amounts of oxygen could lead to a significant increase in the concentration of rotundone in finished wines. Conversely, different doses of sulfur dioxide or storage temperature of the wines had no effect on this compound.

Modeling the Impacts of Weather and Cultural Factors on Rotundone Concentration in Cool-Climate Noiret Wine Grapes.

The sesquiterpenoid rotundone is the compound responsible for the “black pepper” aroma of many plant species, including several economically important wine grape varieties. Since its identification in wine in 2008, there has been an increased interest in understanding how individual climatic or cultural factors affect the accumulation of rotundone in grapes and subsequently the level of wine “pepperiness.” However, no study has assessed climatic and viticultural factors together to identify which variables have the strongest influence on rotundone accumulation. Our study aimed to fill this knowledge gap by developing a predictive model that identified factors that explain rotundone concentrations in Noiret (Vitis sp.) grapes at harvest. Over the 2016 and 2017 seasons, we measured 21 viticultural, meso- and microclimatic variables and concentrations of rotundone in Noiret wine grapes at seven vineyards in the northeastern U.S. Vineyard growing degree days (GDDv) and the amount of solar radiation (cumulative solar exposure; CSEv) accumulated from the beginning of fruit ripening to harvest were the variables best correlated (r = 0.70 and r = 0.74, respectively) with rotundone concentrations. Linear correlations between microclimatic parameters and rotundone concentrations were weaker, but overall rotundone was negatively correlated with low (<15°C) and high (>30°C) berry temperatures. Using the 2-year data set we were able to develop a four-variable model which explained more than 80% of the variation in rotundone concentration at harvest. The model included weather [growing degree days during fruit ripening (GDDv)] and plant-related variables (concentrations of phosphorus and calcium in the leaf petiole, and crop load). The model we developed could be used by wine producers to identify sites or cultural practices that favor rotundone accumulation in Noiret grapes after performing a model validation with an additional, external data set. More broadly, the statistical approach used here could be applied to other studies that also seek to assess the effects of multiple factors on a variable of interest under varying environmental conditions.

Using common viticultural practices to modulate the rotundone and 3-isobutyl-2-methoxypyrazine composition of Vitis vinifera L. cv. Fer N red wines from a temperate climate wine region with very cool nights

Aim: Rotundone and 3-isobutyl-2-methoxypyrazine (IBMP) are two potent aroma compounds responsible for pepper and bell pepper notes in red wines, respectively. The aim of the study was to modulate, through common viticultural practices, the volatile composition in these two molecules of Fer red wines from a temperate climate wine region with very cool nights, located in the southwest of France.Methods and results: Three viticultural practices (leaf removal 10 days after berry set, removal of lateral shoots, and delayed harvest 7 days after the control) were investigated in 2015 and in 2016. Rotundone concentrations up to 69 ng/L were found in experimental wines. IBMP concentrations were below perception level in wines from 2016 and below detection level in wines from 2015, a vintage with particularly hot climatic conditions between berry set and bunch closure. Delayed harvest induced an increase in rotundone concentration while leaf removal and the removal of lateral shoots had no significant impact on rotundone concentration. Delayed harvest and the removal of lateral shoots were the most efficient practices to decrease IBMP in wines. The three techniques made it possible to increase the odour activity values (OAV) ratio of OAV rotundone to OAV IBMP, with the greatest impact observed for delayed harvest.Conclusion: According to our results, delayed harvest appears to be the best practice to modulate the volatile composition of Fer wines toward an increase in the OAV rotundone to OAV IBMP ratio.Significance and impact of the study: Our results may assist local grape growers to modulate the volatile composition of their wines.

Microbes at the root of wine’s peppery flavor

Terroir—from the French word for soil—describes how local soil, climate, and geography affect the flavor of wine. Research at an Australian vineyard suggests that microbes in the soil make their own important contributions to terroir, changing the flavor of the wines made from the grapes that are grown there (Front. Microbiol. 2019, DOI: 10.3389/fmicb.2019.01607). Australia’s Victoria wine region has a cool climate and produces distinctive peppery wines from the Syrah grape, known locally as Shiraz. This spicy flavor is thanks to the sesquiterpene molecule called rotundone. But rotundone levels vary among vines, even in the same vineyard. Sequencing the DNA of soil microbes from one vineyard, Gupta Vadakattu at the Commonwealth Scientific and Industrial Research Organisation in Urrbrae and coworkers found higher rotundone concentrations in grapes grown in soil that had a high bacterial diversity but low fungal diversity. While it’s not clear exactly how the bacteria are influencing the

A 2-year multisite study of viticultural and environmental factors affecting rotundone concentration in Duras red wine

Aim: A study was carried out in 2013 and 2014 to determine the key environmental and viticultural variables affecting the concentration of rotundone, the black pepper aroma compound, in Vitis vinifera L. cv. Duras red wines at 10 different vineyard blocks.Methods and Results: For each block, data for fruit quality attributes, as well as climatic and agronomical variables, were collected. Rotundone was quantified in wines prepared by microvinification techniques (in a 1-L Erlenmeyer flask). Rotundone concentration varied across blocks from 63 ng/L to 239 ng/L in 2013 and from 25 ng/L to 115 ng/L in 2014. Three separate partial least squares regression models were constructed to predict rotundone concentration in wines in 2013, in 2014, and in both vintages. Gluconic acid, a secondary metabolite of Botrytis cinerea, had a substantial contribution to the 2013 and multivintage models, with a negative regression coefficient with rotundone concentration. Other predictors were associated with abiotic factors such as cumulative rainfall, thermal index, hours of sunshine and mean daily irradiation.Conclusions: Our results indicate that mesoscale climatic variables are the key factors determining rotundone concentration, and also suggest that Botrytis cinerea may be involved in rotundone degradation.Significance and impact of the study: Our findings may assist grape growers producing Duras red wines to select specific vineyard blocks with the aim of producing wines with a desired rotundone concentration. They also open up new fields of investigation into mechanisms involved in possible rotundone degradation by Botrytis cinerea.

Vineyard Soil Microbiome Composition Related to Rotundone Concentration in Australian Cool Climate 'Peppery' Shiraz Grapes.

Soil microbial communities have an integral association with plants and play an important role in shaping plant nutrition, health, crop productivity and product quality. The influence of bacteria and fungi on wine fermentation is well known. However, little is known about the role of soil microbes, other than microbial pathogens, on grape composition or their role in vintage or site (terroir) impacts on grape composition. In this study, we used an amplicon sequencing approach to investigate the potential relationships between soil microbes and inherent spatial variation in grape metabolite composition – specifically, the concentration of the ‘impact aroma compound’ rotundone in Shiraz grapes (Vitis vinifera L.) grown in a 6.1 ha vineyard in the Grampians region of Victoria, Australia. Previous work had demonstrated temporal stability in patterns of within-vineyard spatial variation in rotundone concentration, enabling identification of defined ‘zones’ of inherently ‘low’ or ‘high’ concentration of this grape metabolite. 16S rRNA and ITS region-amplicon sequencing analysis of microbial communities in the surface soils collected from these zones indicated marked differences between zones in the genetic diversity and composition of the soil bacterial and fungal microbiome. Soils in the High rotundone zone exhibited higher diversity of bacteria, but lower diversity of fungi, compared to the soils in the Low rotundone zone. In addition, the network analysis of the microbial community in the High rotundone zone soils appeared well structured, especially with respect to the bacterial community, compared to that in the Low rotundone zone soils. The key differences in the microbial community structure between the rotundone zones are obvious for taxa/groups of both bacteria and fungi, particularly for bacteria belonging to Acidobacteria-GP4 and GP7, Rhizobiales, Gaiellaceae, Alphaproteobacteria and the Nectriaceae and Tremellaceae families of fungi. Although mulching in some parts of the vineyard caused changes in bacterial and fungal composition and overall microbial catabolic diversity and activity, its effects did not mask the rotundone zone-based variation. This finding of a systematic rotundone zone-based variation in soil microbiomes suggests an opportunity to bring together understanding of microbial ecology, plant biochemistry, and viticultural management for improved management of grape metabolism, composition and wine flavor.

Impact of Fruit-Zone Leaf Removal on Rotundone Concentration in Noiret

Rotundone was recently identified as the compound that imparts the black pepper aroma in several winegrape cultivars. This two-year study aimed to identify the presence of rotundone in Noiret (interspecific hybrid of Vitis) and to determine the impact of fruit-zone leaf removal on rotundone concentrations in fruit and wine. The relationship between the intensity of black pepper aroma and rotundone concentration in Noiret wine was also explored. An undefoliated control (CON) was compared to a maintained fruit-zone sunlight exposure (MSE) treatment, where leaves were periodically removed from the fruit-zone. The influence of timing of fruit-zone leaf removal was assessed in a separate experiment by comparing preveraison leaf removal (LR) and postveraison leaf removal (PVLR) treatments. MSE vines had greater fruit-zone sunlight exposure compared to the CON throughout the season in 2015, both at the pre- and postveraison stages, but in 2014, only after veraison. PVLR increased fruit-zone sunlight exposure during ripening compared to LR in 2015 only. Rotundone could not be quantified in Noiret berries sampled before or at veraison (limit of quantitation = 0.16 μg/kg). Rotundone concentrations in harvested fruit and wines did not differ between treatments in 2014, but were significantly higher in MSE than in CON in 2015 (1.98 versus 1.28 μg/kg). PVLR temporarily increased rotundone concentration compared to LR, but differences disappeared by harvest. Black pepper aroma intensity, as determined by a sensory panel, was positively correlated (p = 0.023, r = 0.791) with rotundone concentration in wines made from imposed viticulture treatments, providing evidence that black pepper notes in Noiret are positively related to concentration of rotundone in the wine.

Can a certain concentration of rotundone be undesirable in Duras red wine? A study to estimate a consumer rejection threshold for the pepper aroma compound

Background and Aims Rotundone is responsible for peppery aroma in wine. This note is not appreciated by all consumers, which indicates that rotundone might be considered as a taint above a certain concentration. The current study aimed at determining a consumer rejection threshold for rotundone in Duras red wine. Methods and Results Consumers (n = 62) received pairs of samples consisting of a base wine and the base wine spiked with an ascending concentration of rotundone and were asked to indicate which sample they preferred. Anosmic respondents detected through triangle tests represented 31% of the panellists. For these panellists, the wine spiked at the lowest concentration was significantly rejected suggesting that rotundone might induce a trigeminal sensation and/or is involved in molecular mechanisms of flavour reduction. For remaining panellists, we were not able to determine any consumer rejection threshold. We identified three clusters of consumer profiles. The first cluster preferred a moderate concentration of rotundone and rejected a high concentration. The second cluster, mainly composed of young consumers, preferred the Control. The last group appreciated peppery wines especially at high concentration. Conclusions The response of consumers to rotundone is complex, and peppery notes are perceived positively or in a neutral manner by most consumers with the exception of young panellists. Significance of the Study Our results may assist grape growers producing Duras and other cultivars, where rotundone makes a sensory contribution, to adapt their products to consumer profiles. They also open new fields of investigation into mechanisms involved in specific anosmia to rotundone.

Fortification and Elevated Alcohol Concentration Affect the Concentration of Rotundone and Volatiles in Vitis vinifera cv. Shiraz Wine

Rotundone is a key aromatic compound for cool-climate Shiraz. This compound is produced in the skin of grape berries and extracted into wine during fermentation. This project investigated the influence of fermentation techniques on the concentration of rotundone in the resultant wine. Wine was fortified with ethanol and sucrose on the 1st and 5th days of fermentation and rotundone, volatile aroma compounds and colour were assessed in the resultant wine. The relationship between the concentration of rotundone and alcoholic strength during fermentation process was also investigated. Wine alcoholic strength and skin–wine contact time were two factors affecting rotundone extraction rate from grapes into wine. Fortification significantly enhanced rotundone extraction rate, and improved wine colour and phenolics and affects the concentration of ethyl acetate, 3-methylbutyl acetate, ethyl butanoate, ethyl hexanoate, ethyl octanoate, methyl nonanoate, isopentanol and phenylethyl alcohol in the resultant wine. Understanding how ethanol produced during fermentation can change the extraction of skin-bound aroma compounds and the colour and flavour of wine allows greater control of fermentation parameters to produce quality wine.

Impact of Winemaking Techniques on Classical Enological Parameters and Rotundone in Red Wine at the Laboratory Scale

The impact of fermentation variables (time and temperature of maceration, yeast species, addition of pectolytic enzymes) and winemaking techniques (cold soak, thermovinification, carbonic maceration, and rose vinification) on rotundone and classical enological parameters was investigated in triplicate in red wine made from Duras at the laboratory scale. Rotundone was poorly correlated to anthocyanins and to total phenolic index, some variables reflecting the extraction of skin compounds, which suggests that the solubility of rotundone or its ability to bind to other materials may differ from anthocyanins and most of the grape proanthocyanidins. Compared with control wine, wines made from a rose and a thermovinification treatment differed largely in their enological parameters. These two treatments involving a preferment removal of skins resulted in the lowest wine rotundone concentrations of ~20% and 13%, respectively. The other treatments had a weak impact on the studied parameters, and none of them, including the use of macerating enzymes and the increase in temperature or time of maceration, resulted in enhanced rotundone concentrations. Semicarbonic maceration, fermentation with Saccharomyces uvarum, or longer skin contact during postfermentation maceration resulted in wine with a significant decrease of ~20% in rotundone concentration, indicating practical opportunities for reducing pepper aroma in wine.

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.

Distribution of Rotundone and Possible Translocation of Related Compounds Amongst Grapevine Tissues in Vitis vinifera L. cv. Shiraz.

Rotundone is an attractive wine aroma compound, especially important for cool climate Shiraz. Its presence in wine is mainly from the grape skin, but can also be found in non-grape tissues, such as leaves and stems. Whether rotundone is produced independently within different grapevine tissues or transported amongst non-grape tissues and grape berries remains unclear. The current study investigated the distribution of this compound in different vine tissues during development and studied the most likely mode of rotundone translocation—via phloem—using stable isotope feeding. In addition, local production of rotundone induced by herbivore feeding was assessed. Results showed that rotundone was firstly detected in the petioles and peduncles/rachises within the development of Vitis vinifera L. cv. Shiraz. Different grapevine tissues had a similar pattern of rotundone production at different grape developmental stages. In the individual vine shoots, non-grape tissues contained higher concentrations and amounts of rotundone compared to berries, which showed that non-grape tissues were the larger pool of rotundone within the plant. This study confirmed the local production of rotundone in individual tissues and ruled out the possibility of phloem translocation of rotundone between different tissues. In addition, other terpenes, including one monoterpenoid (geraniol) and six sesquiterpenes (clovene, α-ylangene, β-copaene, α-muurolene, δ-cadinene, and cis/trans-calamenene) were, for the first time, detected in the ethylenediaminetetraacetic acid-facilitated petiole phloem exudates, with their originality unconfirmed. Unlike other herbivore-induced terpenes, herbivorous activity had limited influences on the concentration of rotundone in grapevine leaves.

On-vine grape drying combined with irrigation allows to produce red wines with enhanced phenolic and rotundone concentrations

Rotundone, the compound responsible for peppery aroma in red wines is positively correlated with the absence of water deficit during ripening which can make it problematic to produce red wines combining both superior concentrations in rotundone and phenolic compounds. To reach this double objective, on-vine drying with cutting of the fruit bearing cane or “Passerillage Éclaircissage sur Souche” (PES), a technique that consists in cutting the cane 2–3 weeks prior to harvest on a Guyot-trained vineyard was investigated combined or not with irrigation. We showed that PES had a limited impact on rotundone in wine. As the PES technique leads to an interruption of the sap flow, our results suggest that rotundone is synthesized in the berries and not translocated. A viticultural system combining irrigation and then PES induced significant gains in rotundone, in sugar concentration, in anthocyanins and in Total Phenolic Index in wine, and in skin to juice ratio. Measurements of bunch surface temperature indicate that the enhancement of rotundone production induced by irrigation is likely to be due to a direct rather than to an indirect effect through an increase in leaf area leading to a cooler bunch microclimate.

A sensory, chemical and consumer study of the peppery typicality of French gamay wines from cool-climate vineyards

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: Within the protected designation of origin (PDO) Côtes d’Auvergne, Gamay N wines express unique peppery notes that may reflect high levels of rotundone. We investigated the typicality of these wines by determining their sensory, chemical and consumer profiles.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Twenty-one Gamay N wines from the 2013 vintage from four French wine-growing areas were assessed by a trained sensory panel (n = 8). Principal component analysis and hierarchical clustering of olfactory data were used to describe differences among regions and to select four wines for a consumer study (n = 87). Gamay N wines from Auvergne had more intense peppery notes and higher rotundone concentrations, two characteristics that showed a significant positive correlation. The large variability in rotundone among the 12 wines from Auvergne was attributed to ethanol content, which was correlated to the rotundone levels in the wines. Those who appreciate wines with a peppery sensory profile were generally managers and professionals who are willing to pay more for a bottle of wine.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: There were differences in sensory profile and rotundone concentrations in Gamay N wines from cool-climate vineyards. We also identified the consumption profile of those who appreciate peppery wines.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: Our results provide a scientific foundation for Auvergne grape growers to promote the typicality of their wines. This research also identifies the key elements for developing the Côtes d’Auvergne wine range and adapting products to consumer profiles.&lt;/p&gt;

Certified clone and powdery mildew impact rotundone in red wine from &lt;i&gt;Vitis vinifera L.&lt;/i&gt; cv. Duras N

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: Few recent studies have been investigating the effect of clone on aroma compounds. The aim of this research work was to study the impact of certified clones from &lt;em&gt;Vitis vinifera &lt;/em&gt;L. cv. Duras N on grape quality and rotundone, a sesquiterpene responsible for peppery aroma which has been reported recently in red wines made from this cultivar.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: The experimental site consisted of four consecutive rows, each row planted with one of the four certified clones of Duras N (554, 555, 627 and 654). For each clone, measurements were replicated on three experimental units per row. Each experimental unit consisted of twelve continuous vines. Rotundone concentration was measured in wines prepared by microvinification techniques (1-L Erlenmeyer flasks). For both vintages of study, rotundone concentrations were significantly higher in wines from clones 554 and 654 in comparison with clone 555, while clone 627 showed an intermediate level. In 2014, differences in powdery mildew (PM) severity on clusters were identified between the four clones and a positive logarithmic correlation (r&lt;sup&gt;2&lt;/sup&gt; = 0.58) was reported on the experimental site between rotundone in wines and PM severity on grapes.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusion&lt;/strong&gt;: Our results found differences in rotundone concentrations in wines made from the four Duras N certified clones. The results also suggested that grapevine defence response to PM could enhance rotundone production in berries. Clonal differences in susceptibility to biotic stress, such as PM, might explain the differences observed in rotundone concentrations between the four studied clones.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: Our results may assist grape growers to produce high quality wines with a desired aroma attribute made from Duras N. One should consider planting clone 554 in order to promote high levels of rotundone in wines made from this cultivar.&lt;/p&gt;

Environmental Factors and Seasonality Affect the Concentration of Rotundone in Vitis vinifera L. cv. Shiraz Wine.

Rotundone is a sesquiterpene that gives grapes and wine a desirable ‘peppery’ aroma. Previous research has reported that growing grapevines in a cool climate is an important factor that drives rotundone accumulation in grape berries and wine. This study used historical data sets to investigate which weather parameters are mostly influencing rotundone concentration in grape berries and wine. For this purpose, wines produced from 15 vintages from the same Shiraz vineyard (The Old Block, Mount Langi Ghiran, Victoria, Australia) were analysed for rotundone concentration and compared to comprehensive weather data and minimal temperature information. Degree hours were obtained by interpolating available temperature information from the vineyard site using a simple piecewise cubic hermite interpolating polynomial method (PCHIP). Results showed that the highest concentrations of rotundone were consistently found in wines from cool and wet seasons. The Principal Component Analysis (PCA) showed that the concentration of rotundone in wine was negatively correlated with daily solar exposure and grape bunch zone temperature, and positively correlated with vineyard water balance. Finally, models were constructed based on the Gompertz function to describe the dynamics of rotundone concentration in berries through the ripening process according to phenological and thermal times. This characterisation is an important step forward to potentially predict the final quality of the resultant wines based on the evolution of specific compounds in berries according to critical environmental and micrometeorological variables. The modelling techniques described in this paper were able to describe the behaviour of rotundone concentration based on seasonal weather conditions and grapevine phenological stages, and could be potentially used to predict the final rotundone concentration early in future growing seasons. This could enable the adoption of precision irrigation and canopy management strategies to effectively mitigate adverse impacts related to climate change and microclimatic variability, such as heat waves, within a vineyard on wine quality.

Analysis of Rotundone in Japanese Syrah Grapes and Wines using Stir Bar Sorptive Extraction (SBSE) with Heart-Cutting Two-Dimensional GC-MS

Rotundone, an oxygenated sesquiterpene, is responsible for the peppery aroma in wines. We developed an effective and simple method to determine trace levels of rotundone in grapes and wines. The method uses stir bar sorptive extraction (SBSE) with heart-cutting two-dimensional gas chromatography/mass spectrometry without a pre-extraction process such as solid-phase extraction. The limits of detection and quantitation for rotundone were 2.1 and 6.5 ng/kg in grape and 2.4 and 7.2 ng/L in wine. The recoveries of rotundone from Cabernet Sauvignon grape and wine were 106% (spiked with 120 ng/kg for grape) and 96% (spiked with 120 ng/L for wine), respectively. We demonstrated that rotundone concentrations in Syrah grapes and wines from Ueda were higher (up to 2342 ng/kg and 232 ng/L, respectively) than the maximal rotundone concentrations in Australian Syrah grapes and wines. Findings indicate that some environmental factors in Japan may promote rotundone accumulation in Syrah grapes, and underscores the importance of studying regional characteristics of rotundone accumulation in Syrah grapes.

Shiraz wines made from grape berries (Vitis vinifera) delayed in ripening by plant growth regulator treatment have elevated rotundone concentrations and "pepper" flavor and aroma.

Preveraison treatment of Shiraz berries with either 1-naphthaleneacetic acid (NAA) or Ethrel delayed the onset of ripening and harvest. NAA was more effective than Ethrel, delaying harvest by 23 days, compared to 6 days for Ethrel. Sensory analysis of wines from NAA-treated fruit showed significant differences in 10 attributes, including higher "pepper" flavor and aroma compared to those of the control wines. A nontargeted analysis of headspace volatiles revealed modest differences between wines made from control and NAA- or Ethrel-treated berries. However, the concentration of rotundone, the metabolite responsible for the pepper character, was below the level of detection by solid phase microextraction-gas chromatography-mass spectrometry in control wines, low in Ethrel wines (2 ng/L), and much higher in NAA wines (29 ng/L). Thus, NAA, and to a lesser extent Ethrel, treatment of grapes during the preveraison period can delay ripening and enhance rotundone concentrations in Shiraz fruit, thereby enhancing wine "peppery" attributes.

Effect of ripeness and viticultural techniques on the rotundone concentration in red wine made fromVitis vinifera L. cv. Duras

Background and Aims Rotundone, a potent aroma compound responsible for peppery aroma and flavour in Shiraz, was detected recently in Vitis vinifera L. cv. Duras wines. In 2011 and 2012, two separate experiments were carried out to determine the effect of ripeness and viticultural techniques on rotundone concentration in Duras wine. Methods and Results Rotundone was measured in wines prepared by microvinification techniques (1 L Erlenmeyer). Accumulation of this compound in wines depended on vintage conditions and the degree of ripening, such that a higher concentration of rotundone was reached 44 days after mid-veraison. Application of exogenous jasmonic acid and grape thinning did not significantly affect rotundone concentration, whereas leaf removal strongly reduced rotundone concentration. Wine from the irrigated treatment had a higher concentration of rotundone, and in most cases, vine water status over the veraison–harvest period was identified as a key variable that was well correlated with observed intraplot variability. Conclusions These findings confirm that some common viticultural practices can be used to manipulate the peppery character in red wine. Significance of the Study Our results may assist grape growers to produce Duras, Shiraz and other cultivars where rotundone makes an important contribution to wine aroma.