ARC Training Centre for Innovative Wine Production publications

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Open Access
3D visualisation of voids in grapevine flowers and berries using X‐ray micro computed tomography
(Wiley, 2021) Xiao, Z.; Stait‐Gardner, T.; Willis, S.A.; Price, W.S.; Moroni, F.J.; Pagay, V.; Tyerman, S.D.; Schmidtke, L.M.; Rogiers, S.Y.
Background and Aim: X-ray micro computed tomography (micro-CT) is a non-destructive 3D imaging technique that has been applied to plant morphology and anatomical studies to gain a better understanding of physiological phenomena in vivo. It is particularly useful for imaging voids in undisturbed fragile tissues and therefore may be applied to the delicate flowers and soft berries of Vitis vinifera. The characterisation of gas spaces and channels can offer insights into the process of tissue aeration and this may have implications on cell function and vitality. We assessed the use of micro-CT to visualise voids within these reproductive organs. Methods and Results: The internal structures of flowers and berries were captured through rapid micro-CT scanning and subsequently were recreated in 3D using image processing. The relative positions of the developing flower parts encased within the flower cap were visualised. Low density/porous tissue was identified within the pedicel and receptacle, con- necting the lenticels with the interior of the berry. Voids were present in the proximal mesocarp of mature berries forming a ‘detachment zone’ in both seeded and seedless cultivars. Voids permeated the mesocarp of mature seedless grape cultivars, but not seeded grapes. Conclusion: Micro-CT offers new insights regarding the distribution of voids on the morphology and compositional hetero- geneity of organs that are difficult to dissect and/or view with light microscopy. Significance of the Study: A better understanding of the physiology and functionality of grapevine reproductive tissues may be achieved by 3D visualisation of internal structure in vivo.
Open Access
A review of wine authentication using spectroscopic approaches in combination with chemometrics
(MDPI AG, 2021) Ranaweera, R.K.R.; Capone, D.L.; Bastian, S.E.P.; Cozzolino, D.; Jeffery, D.W.
In a global context where trading of wines involves considerable economic value, the requirement to guarantee wine authenticity can never be underestimated. With the ever-increasing advancements in analytical platforms, research into spectroscopic methods is thriving as they offer a powerful tool for rapid wine authentication. In particular, spectroscopic techniques have been identified as a user-friendly and economical alternative to traditional analyses involving more complex instrumentation that may not readily be deployable in an industry setting. Chemometrics plays an indispensable role in the interpretation and modelling of spectral data and is frequently used in conjunction with spectroscopy for sample classification. Considering the variety of available techniques under the banner of spectroscopy, this review aims to provide an update on the most popular spectroscopic approaches and chemometric data analysis procedures that are applicable to wine authentication.
Open Access
A systematic review and meta-analysis of vineyard techniques used to delay ripening
(Oxford University Press (OUP), 2022) Previtali, P.; Giorgini, F.; Mullen, R.S.; Dookozlian, N.K.; Wilkinson, K.L.; Ford, C.M.
Several vineyard techniques have been proposed to delay grape maturity in light of the advanced maturation driven by increasingly frequent water and heat stress events that are detrimental to grape quality. These studies differ in terms of their experimental conditions, and in the present work we have attempted to summarize previous observations in a quantitative, data-driven systematic review. A meta-analysis of quantitative data gathered across 43 relevant studies revealed the overall significance of the proposed treatments and evaluated the impact of different experimental conditions on the outcome of antitranspirants, delayed pruning and late source limitation. Antitranspirants were most effective when applied twice and closer to veraison, while di-1-p-menthene increased the ripening delay by about 1 °Brix compared to kaolin. Larger ripening delays were achieved with delayed pruning of low-yielding vines or by pruning at later stages of apical bud development. Late defoliation or shoot trimming delayed ripening in high-yielding vines and represent suitable solutions for late-harvested varieties, but became ineffective where the treatment decreased yield. This quantitative meta-analysis of 242 primary observations uncovers factors affecting the efficacy of vineyard practices to delay ripening, which should be carefully considered by grape growers attempting to achieve this outcome.
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Absorbance-transmission and fluorescence excitation-emission matrix (A-TEEM) with multi-block data analysis and machine learning for accurate intraregional classification of Barossa Shiraz wine
(Elsevier, 2023) Ranaweera, R.K.R.; Bastian, S.E.P.; Gilmore, A.M.; Capone, D.L.; Jeffery, D.W.
Authentication of wine can be considered at different scales, with classification according to country, province/ state, or appellation/wine producing region. An absorbance-transmission and excitation-emission matrix (ATEEM) technique was applied for the first time to examine intraregional differences, using Shiraz wines (n = 186) produced during three vintages from five subregions of Barossa Valley and from Eden Valley. Absorption spectra and EEM fingerprints were modelled as a multi-block data set for initial exploration with k-means cluster analysis and principal component analysis, and then with machine learning modelling using extreme gradient boosting discriminant analysis (XGBDA). Whereas some clustering was evident with the initial unsupervised approaches, classification with XGBDA afforded an impressive 100% correct class assignment for subregion and vintage year. Extending the utility and novelty of the A-TEEM approach, predictive models for chemical parameters (alcohol, glucose + fructose, pH, titratable acidity, and volatile acidity) were also validated using ATEEM data with XGB regression.
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Accumulation of volatile phenol glycoconjugates in grapes following grapevine exposure to smoke and potential mitigation of smoke taint by foliar application of kaolin
(Springer, 2019) van der Hulst, L.; Munguia, P.; Culbert, J.A.; Ford, C.M.; Burton, R.A.; Wilkinson, K.L.
Main Conclusion: The accumulation of volatile phenol glycoconjugates in smoke-exposed grapes was monitored following grapevine exposure to smoke, with different glycoconjugate profiles observed for fruit sampled 1 and 7 days after smoke exposure, and at maturity. Foliar application of kaolin reduced the concentration of volatile phenol glycoconjugates in smoke-exposed fruit, but efficacy depended on the rate of application and extent of coverage. Smoke taint can be found in wines made from grapes exposed to smoke from bushfires or prescribed burns. It is characterized by objectionable smoky and ashy aromas and flavors, which have been attributed to the presence of smoke-derived volatile phenols, in free and glycoconjugate forms. This study investigated: (1) the accumulation of volatile phenol glycoconjugates in grapes following the application of smoke to Sauvignon Blanc, Chardonnay and Merlot grapevines at approximately 10 days post-veraison; and (2) the potential mitigation of smoke taint as a consequence of foliar applications of kaolin (a clay-based protective film) prior to grapevine smoke exposure. Varietal differences were observed in the glycoconjugate profiles of smoke-exposed grapes; the highest glycoconjugate levels were found in Merlot grapes, being pentose-glucosides of guaiacol, cresols, and phenol, and gentiobiosides of guaiacol and syringol. Changes in volatile phenol glycoconjugate profiles were also observed with time, i.e., between fruit sampled 1 day after smoke exposure and at maturity. The application of kaolin did not significantly affect the glycoconjugate profiles of Sauvignon Blanc and Chardonnay grapes, but significantly lower volatile phenol glycoconjugate levels were observed in Merlot fruit that was treated with kaolin prior to smoke exposure. The potential for control and smoke-exposed grapes to be differentiated by measurement of spectral reflectance was also demonstrated.
Open Access
Amelioration of Smoke Taint in Cabernet Sauvignon Wine via Post-Harvest Ozonation of Grapes
(MDPI AG, 2021) Modesti, M.; Szeto, C.; Ristic, R.; Jiang, W.; Culbert, J.; Catelli, C.; Mencarelli, F.; Tonutti, P.; Wilkinson, K.
Strategies that mitigate the negative effects of vineyard exposure to smoke on wine composition and sensory properties are needed to address the recurring incidence of bushfires in or near wine regions. Recent research demonstrated the potential for post-harvest ozonation of moderately smoke-exposed grapes to reduce both the concentration of smoke taint marker compounds (i.e., volatile phenols and their glycosides) and the perceived intensity of smoke taint in wine, depending on the dose and duration of ozone treatment. The current study further evaluated the efficacy of ozonation as a method for the amelioration of smoke taint in wine by comparing the chemical and sensory consequences of post-harvest ozonation (at 1 ppm for 24 h) of Cabernet Sauvignon grapes following grapevine exposure to dense smoke, i.e., ozone treatment of more heavily tainted grapes. Ozonation again yielded significant reductions in the concentration of free and glycosylated volatile phenols—up to 25% and 30%, respectively. However, although the intensities of smoke-related sensory attributes were generally lower in wines made with smoke-exposed grapes that were ozonated (compared to wines made with smoke-exposed grapes that were not ozonated), the results were not statistically significant. This suggests that the efficacy of ozone treatment depends on the extent to which grapes have been tainted by smoke.
Open Access
Analysis of potent odour-active volatile thiols in foods and beverages with a focus on wine
(MDPI, 2019) Chen, L.; Capone, D.; Jeffery, D.
Certain volatile thiols are some of the most potent odour-active molecules that are found in nature. Thiols play significant roles in the aroma qualities of a range of foods and beverages, including wine, with extremely low odour detection thresholds (nanogram per litre range). A fundamental understanding of their formation, fate, and impact essentially depends on the development of suitable analytical methods. The analysis of volatile thiols in foods and beverages is a challenging task when considering (1) the complexity of food and beverage matrices and (2) that thiols are highly reactive, low molecular-weight volatiles that are generally present at trace to ultra-trace concentrations. For the past three decades, the analytical evaluation of volatile thiols has been intensively performed in various foods and beverages, and many novel techniques related to derivatisation, isolation, separation, and detection have been developed, particularly by wine researchers. This review aims to provide an up-to-date overview of the major analytical methodologies that are proposed for potent volatile thiol analysis in wine, foods, and other beverages. The analytical challenges for thiol analysis in foods and beverages are outlined, and the main analytical methods and recent advances in methodology are summarised and evaluated for their strengths and limitations. The key analytical aspects reviewed include derivatisation and sample preparation techniques, chromatographic separation, mass spectrometric detection, matrix effects, and quantitative analysis. In addition, future perspectives on volatile thiol research are also suggested
Open Access
Applying nanoparticle tracking analysis to characterize the polydispersity of aggregates resulting from tannin-polysaccharide interactions in wine-like media
(MDPI AG, 2019) Li, S.; Wilkinson, K.L.; Mierczynska-Vasilev, A.; Bindon, K.A.
Interactions between grape seed tannin and either a mannoprotein or an arabinogalactan in model wine solutions of different ethanol concentrations were characterized with nanoparticle tracking analysis (NTA), UV-visible spectroscopy and dynamic light scattering (DLS). NTA results reflected a shift in particle size distribution due to aggregation. Furthermore, the light scattering intensity of each tracked particle measured by NTA demonstrated the presence of aggregates, even when a shift in particle size was not apparent. Mannoprotein and arabinogalactan behaved differently when combined with seed tannin. Mannoprotein formed large, highly light-scattering aggregates, while arabinogalactan exhibited only weak interactions with seed tannin. A 3% difference in alcohol concentration of the model solution (12 vs. 15% v/v) was sufficient to affect the interactions between mannoprotein and tannin when the tannin concentration was high. In summary, this study showed that NTA is a promising tool for measuring polydisperse samples of grape and wine macromolecules, and their aggregates under wine-like conditions. The implications for wine colloidal properties are discussed based on these results.
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Authentication of the geographical origin of Australian Cabernet Sauvignon wines using spectrofluorometric and multi-element analyses with multivariate statistical modelling
(Elsevier, 2021) Ranaweera, R.K.R.; Gilmore, A.M.; Capone, D.L.; Bastian, S.E.P.; Jeffery, D.W.
With the increased risk of wine fraud, a rapid and simple method for wine authentication has become a necessity for the global wine industry. The use of fluorescence data from an absorbance and transmission excitation-emission matrix (A-TEEM) technique for discrimination of wines according to geographical origin was investigated in comparison to inductively coupled plasma-mass spectrometry (ICP-MS). The two approaches were applied to commercial Cabernet Sauvignon wines from vintage 2015 originating from three wine regions of Australia, along with Bordeaux, France. Extreme gradient boosting discriminant analysis (XGBDA) was examined among other multivariate algorithms for classification of wines. Models were cross-validated and performance was described in terms of sensitivity, specificity, and accuracy. XGBDA classification afforded 100% correct class assignment for all tested regions using the EEM of each sample, and overall 97.7% for ICP-MS. The novel combination of A-TEEM and XGBDA was found to have great potential for accurate authentication of wines.
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Authenticity and traceability in the wine industry: From analytical chemistry to consumer perceptions
(Elsevier, 2021) Ranaweera, R.; Souza Gonzaga, L.; Capone, D.; Bastian, S.; Jeffery, D.; Cifuentes, A.
Wine has been a part of human history for millennia and is an economically important global industry. Wine is considered as a luxury product, which makes it highly susceptible to fraud and adulteration. Authentication methods and traceability systems designed to protect wine provenance and quality have therefore gained the interest of both researchers and the wine industry. Analytical approaches in combination with chemometrics can authenticate wine by identifying and modeling specific chemical markers or spectral fingerprints. Traceability systems can track and record movements in the supply chain, and by using various devices (e.g., tags, seals, smart phones), can even transmit information to the consumer to provide confidence in the authenticity of a wine. Beyond systems that help in the detection and delivery of an authentic product, the wine industry can also use marketing tools to convey an authentic image and target consumers in an engaging way. This requires an understanding of authenticity from the consumer perspective.
Open Access
Capturing yeast associated with grapes and spontaneous fermentations of the Negro Saurí minority variety from an experimental vineyard near León
(Springer Science and Business Media, 2021) González-Alonso, I.; Walker, M.E.; Pascual-Vallejo, M.-E.; Naharro-Carrasco, G.; Jiranek, V.
‘Microbial terroir’ relates to the infuence of autochthonous yeasts associated with a grape cultivar on the resultant wine. Geographic region, vineyard site and topography, climate and vintage infuence the biodiversity of these microbial communities. Current research focus attempts to correlate their ‘microbial fngerprint’ to the sensorial and chemical characteristics of varietal wines from distinct geographical wine regions. This study focuses on the minor red grape variety, Negro Saurí, which has seen a resurgence in the León Appellation of Origin in Spain as a varietal wine. An experimental vineyard at Melgarajo S.A. (42° 15′ 48.68_N 5° 9′ 56.66_W) was sampled over four consecutive vintages, with autochthonous yeasts being isolated from grapes, must and pilot-scale un-inoculated fermentations, and identifed by ITS sequencing. Forty-nine isolates belonging to Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora uvarum and Torulaspora delbrueckii were isolated from grapes and must, and early stages of fermentation dependent on seasonal variation. Saccharomyces cerevisiae predominated throughout fermentation, as a heterogeneous and dynamic population, with seven major biotypes identifed amongst 110 isolates across four consecutive vintages. Twenty-four S. cerevisiae isolates representing fve strains dominated in two or more vintages. Their persistence through fermentation warrants further validation of their oenological properties as starter cultures
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Changes in wine ethanol content due to evaporation from wine glasses and implications for sensory analysis
(American Chemical Society, 2016) Wollan, D.; Pham, D.; Wilkinson, K.
The relative proportion of water and ethanol present in alcoholic beverages can significantly influence our perception of wine sensory attributes. This study therefore investigated changes in wine ethanol concentration due to evaporation from wine glasses. The ethanol content of commercial wines exposed to ambient conditions whilst in wine glasses was monitored over time. No change in wine ethanol content was observed where glasses were covered with plastic lids, but where glasses were not covered, evaporation had a significant impact on wine ethanol content, with losses from 0.9 to 1.9% alcohol by volume observed for wines that received direct exposure to airflow for 2 hours. Evaporation also resulted in decreases in the concentration of some fermentation volatiles (determined by gas chromatography-mass spectrometry) and a perceptible change in wine aroma. The shape and volume of wine glasses was found to influence evaporation of ethanol. Ethanol evaporated more quickly from wine in certain glasses, which was likely due to increased wine glass opening diameter. The ethanol concentration of wine was found to decrease significantly over time as a consequence of evaporation. The rate of ethanol loss was strongly influenced by exposure to airflow (i.e. from the laboratory air-conditioning unit), together with glass shape and volume. This is the first study to demonstrate the significant potential for ethanol evaporation from wine in wine glasses. Research findings have important implications for the technical evaluation of wine sensory properties; in particular, informal sensory trials and wine show judging, where the use of covers on wine glasses is not standard practice.
Open Access
Chemical and Sensory Profiles of Sauvignon Blanc Wine Following Protein Stabilization Using a Combined Ultrafiltration/Heat/Protease Treatment
(Frontiers, 2022) Sui, Y.; Wollan, D.; McRae, J.M.; Capone, D.L.; Godden, P.; Wilkinson, K.
Ultrafiltration (UF) was evaluated as a process by which proteins can be selectively removed from white wine as an alternative approach to protein stabilization than traditional bentonite fining. Unfined Sauvignon Blanc wine (50 L) was fractionated by UF and the retentate stabilized either by heat and/or protease treatment or bentonite fining before being recombined with the permeate. The heat stability of recombined wine was significantly improved when retentate was heated following protease (Aspergillopepsin) addition and subsequently stabilized by bentonite treatment. The combined UF/heat/protease treatment removed 59% of protein and reduced the quantity of bentonite needed to achieve protein stability by 72%, relative to bentonite treatment alone. This innovative approach to protein stabilization had no significant impact on wine quality or sensory characteristics, affording industry greater confidence in adopting this technology as a novel approach to achieving protein stability.
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Chemical and sensory profiling of Shiraz wines co-fermented with commercial non-Saccharomyces inocula
(Wiley, 2018) Hranilovic, A.; Li, S.; Boss, P.; Bindon, K.; Ristic, R.; Grbin, P.; Van der Westhuizen, T.; Jiranek, V.
Background and Aims: The choice of yeast strain(s) to conduct the fermentation can greatly affect wine chemical and sensory profile. Even though the use of non-Saccharomyces co-inocula to build complexity and diversify styles is increasingly in vogue, a limited number of such products are available to date, and more research is required to guide their use in the wine industry. This study evaluates the potential of commercial yeast inocula to modulate the quality of Shiraz wines at two maturity levels. Methods and Results: Vinification outcomes of eight yeast treatments were compared in earlier (24°Brix) and later (29°Brix) harvested Shiraz fruit. Yeast treatments included five non-Saccharomyces products with sequentially inoculated Saccharomyces cerevisiae, a commercial blend of non-Saccharomyces and S. cerevisiae strains, and a S. cerevisiae inoculum. Fermentation monitoring, and comprehensive analytical profiling in terms of basic chemistry, volatile composition, phenolic measurements and descriptive sensory analysis, allowed for the comparison of the resulting wines. Both harvest date and yeast inoculation treatments had a significant impact on a range of compositional and, in turn, sensory parameters of the wines. Conclusions: Certain non-Saccharomyces sequential inoculation treatments led to increased appeal of earlier harvest wines compared to the S. cerevisiae Control. These treatments, however, were related to an increased risk of arrested fermentation in higher ripeness conditions. Significance of the Study: This study contributes to a better understanding of yeast inoculum-derived modulation of Shiraz wine quality parameters at different maturity levels.
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Chiral analysis of cis-2-methyl-4-propyl-1,3-oxathiane and identification of cis-2,4,4,6-tetramethyl-1,3-oxathiane in wine
(Elsevier, 2021) Wang, X.; Capone, D.L.; Roland, A.; Jeffery, D.W.
cis-2-Methyl-4-propyl-1,3-oxathiane (cis-2-MPO), arising from 3-sulfanylhexan-1-ol (3-SH) and acetaldehyde, was recently identified in wine, but the enantiomeric distribution was unknown. Such information could reveal influences on wine aroma, given the impact of chirality on odorant molecules. Herein, a stable isotope dilution assay employing headspace solid-phase microextraction with chiral gas chromatography–mass spectrometry was developed, validated, and applied to a selection of wines. Studies with (3R)-3-SH revealed the elution order of the cis-2-MPO enantiomers and the concentrations of (2R,4S)-2-MPO and (2S,4R)-2-MPO in the studied wines ranged from undetected to 250 ng/L and 303 ng/L, respectively. Strong positive correlations were found between (3R)-3-SH and (2S,4R)-2-MPO (r = 0.654), and (3S)-3-SH and (2R,4S)-2-MPO (r = 0.860). Additionally, cis- 2,4,4,6-tetramethyl-1,3-oxathiane, constituted from acetaldehyde and 4-methyl-4-sulfanylpentan-2-ol (4- MSPOH), was identified in wine for the first time. This new 1,3-oxathiane, which presents a novel fate for 4- MSPOH, was detected in wines as a single enantiomer at up to 28 ng/L.
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Chiral polyfunctional thiols and their conjugated precursors upon winemaking with five Vitis vinifera Sauvignon blanc clones
(American Chemical Society, 2018) Chen, L.; Capone, D.L.; Tondini, F.A.; Jeffery, D.W.
Five co-located clones of Sauvignon blanc grapes were fermented under controlled conditions at laboratory-scale to investigate the impact of yeast strain, commercial enzyme, or nutrient addition on the concentrations of enantiomers of 3-sulfanylhexan-1-ol (3-SH) and 3-sulfanylhexyl acetate (3-SHA) in resulting wines. The relationship of these enantiomers with the odorless 3-SH precursors present in diastereomeric forms in grape juice was also examined. Possible variations may have existed due to clone type, not only for the diastereomers of 3-SH precursors in juices but also for the enantiomers of 3-SH and 3-SHA in the resulting wines, although there was no obvious stereochemical relationship between precursors and free thiols. From a flavor enhancement perspective, the use of a commercial enzyme in the juice significantly enhanced 3-SH production for some clones. In contrast, less impact on the production of 3-SH and 3-SHA was seen as a result of yeast strain and nutrient regardless of clone type.
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Comparison of consecutive harvests versus blending treatments to produce lower alcohol wines from Cabernet Sauvignon grapes: impact on polysaccharide and tannin content and composition
(Elsevier, 2018) Schelezki, O.; Smith, P.; Hranilovic, A.; Bindon, K.; Jeffery, D.
Abstract not available
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Comparison of consecutive harvests versus blending treatments to produce lower alcohol wines from Cabernet Sauvignon grapes: Impact on wine volatile composition and sensory properties
(Elsevier, 2018) Schelezki, O.J.; Šuklje, K.; Boss, P.K.; Jeffery, D.W.
Abstract not available
Open Access
Compositional consequences of partial dealcoholization of red wine by reverse osmosis-evaporative perstraction
(MDPI, 2019) Pham, D.T.; Stockdale, V.J.; Wollan, D.; Jeffery, D.W.; Wilkinson, K.L.
This study investigated compositional changes in red wines resulting from wine alcohol removal by reverse osmosis-vaporative perstraction (RO-EP) and provides insight into the physical and chemical changes in reduced alcohol wine (RAW). Trial 1 involved RO-EP treatment of three wines that were analyzed pre-treatment, post-treatment, and post-treatment with alcohol adjustment (i.e., addition of ethanol to achieve the original alcohol content). Trial 2 involved partial dealcoholization of two wines and analysis of samples collected during RO-EP treatment, i.e., wine in, wine out, retentate, permeate (pre- and post-EP treatment) and strip water. Wine color was analyzed by spectrophotometric methods, while other compositional changes were determined by WineScan, high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) analyses. In general, RAWs were slightly more concentrated than pre-treatment wines, which resulted in greater color intensity and increased phenolics and organic acids. However, partial dealcoholization resulted in lower concentrations of some fermentation volatiles, particularly ethyl esters, which may reflect ester hydrolysis following ethanol removal.
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Compositional variability in commercial tannin and mannoprotein products
(American Society for Enology and Viticulture, 2018) Li, S.; Wilkinson, K.; Bindon, K.
Enotannin and mannoprotein additives are applied to achieve protein, cold, or color stability in wine, or to modify wine sensory properties. In most cases, the manufacturer only provides basic compositional information and a proposed effect in wine. In this study, 14 grape-based enotannins and eight mannoproteins were sourced from the Australian market, and their composition and molecular size distribution were determined. Diverse product composition was observed for both categories, suggesting that a range of effects could potentially be achieved by applying different products. Moreover, some products showed good agreement between product composition and their designated material of origin, while others showed significant differences.

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