ARC Training Centre for Innovative Wine Production publications

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Lower alcohol wines in the UK market: some baseline consumer behaviour metrics
(Emerald Group, 2014) Bruwer, J.; Jiranek, V.; Halstead, L.; Saliba, A.
Purpose – The purpose of this paper is to provide clearer insights into and identify the key consumer behaviour metrics of the lower alcohol category (<11 per cent ABV) in the UK wine market. Design/methodology/approach – Data were collected via an online survey from a sample size of 598 regular UK wine drinkers. To operationalise the study, five research questions were formulated. A highly structured quantitatively directed questionnaire was designed to find the answers to the research questions. Findings – Barriers to a larger uptake of the product category included non-availability of the products, lower quality perceptions, taste issues, lack of awareness, lack of alcohol's “feel effect” and absence of a lower alcohol drinking occasion. Many UK consumers are not yet convinced how/if lower alcohol wine fits into their wine drinking occasions. The lower ABV wine buyer's main profile characteristics are weighted towards females, Millennial and Baby Boomer age generations, mostly mid to low income, who drink mainly white and rosé wines. Lower alcohol on its own is not seen as a big benefit, thus lower ABV wines should be more creatively communicated to sell the benefits. Originality/value – This study contributes to the knowledge base in that it is the first to investigate consumer behaviour metrics as regards lower ABV wine in one of the world's leading markets, in the process providing some important baseline research information on this category. As such it is of value to academic researchers and practitioners alike.
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New training centre projects to deliver new tools and optimise existing practices for industry
(Winetitles, 2015) Ristic, R.
The University of Adelaide recently received funding from the Australian Research Council to establish a Training Centre for Innovative Wine Production aimed at better placing the wine industry to make the products consumers want.
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Integrated strategies to moderate the alcohol content of wines
(S. Aust Winetitles, 2016) Ristic, R.; Hranilovic, A.; Li, S.; Longo, R.; Pham, D.; Qesja, B.; Schelezki, O.; Jiranek, V.
The ARC Training Centre for Innovative Wine Production reports on some of the outcomes from trials it undertook during the 2014-15 vintage using techniques designed to moderate the alcohol content of wines.
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Spotlight on varietal thiols and precursors in grapes and wines
(CSIRO Publishing, 2016) Jeffery, D.
Wine is an amazingly complex natural product that requires dedicated scientists to resolve many of its mysteries. Traditional synthetic organic chemistry and modern analytical techniques are powerful tools at the disposal of wine chemists who tackle the complexities of wine in order to improve scientific understanding and provide practical solutions to industry. Part of this quest for knowledge relates to maintaining or improving wine quality, which underpins consumer acceptance and links to the competitiveness of wineries in a global market. Wine aroma is an important aspect of wine quality and garners much attention from researchers. Grape-derived aroma compounds are one area of particular importance owing to their distinctiveness and ability to impart ‘varietal aromas’ to wines. Varietal thiols imparting tropical and citrus notes that are characteristic of wines such as Sauvignon Blanc have emerged, along with their grape-derived precursors, as an area of interest over the past two decades. These compounds have also caught our attention and we have made some important contributions to this field, including identifying new precursors, developing novel analytical methods, and conducting studies that provide unique insights into the biochemical transformations occurring in grape berries and juice, and during fermentation.
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Retention of proanthocyanidin in wine-like solution is conferred by a dynamic interaction between soluble and insoluble grape cell wall components
(American Chemical Society, 2016) Bindon, K.A.; Li, S.; Kassara, S.; Smith, P.A.
For better understanding of the factors that impact proanthocyanidin (PA) adsorption by insoluble cell walls or interaction with soluble cell wall-derived components, application of a commercial polygalacturonase enzyme preparation was investigated to modify grape cell wall structure. Soluble and insoluble cell wall material was isolated from the skin and mesocarp components of Vitis vinifera Shiraz grapes. It was observed that significant depolymerization of the insoluble grape cell wall occurred following enzyme application to both grape cell wall fractions, with increased solubilization of rhamnogalacturonan-enriched, low molecular weight polysaccharides. However, in the case of grape mesocarp, the solubilization of protein from cell walls (in buffer) was significant and increased only slightly by the enzyme treatment. Enzyme treatment significantly reduced the adsorption of PA by insoluble cell walls, but this effect was observed only when material solubilized from grape cell walls had been removed. The loss of PA through interaction with the soluble cell wall fraction was observed to be greater for mesocarp than skin cell walls. Subsequent experiments on the soluble mesocarp cell wall fraction confirmed a role for protein in the precipitation of PA. This identified a potential mechanism by which extracted grape PA may be lost from wine during vinification, as a precipitate with solubilized grape mesocarp proteins. Although protein was a minor component in terms of total concentration, losses of PA via precipitation with proteins were in the order of 50% of available PA. PA-induced precipitation could proceed until all protein was removed from solution and may account for the very low levels of residual protein observed in red wines. The results point to a dynamic interaction of grape insoluble and soluble components in modulating PA retention in wine.
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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.
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Understanding Wine Chemistry
(John Wiley & Sons, 2016) Waterhouse, A.L.; Sacks, G.L.; Jeffery, D.W.
Wine chemistry inspires and challenges with its complexity, and while this is intriguing, it can also be a barrier to further understanding. The topic is demystified in Understanding Wine Chemistry, which explains the important chemistry of wine at the level of university education, and provides an accessible reference text for scientists and scientifically trained winemakers alike. Understanding Wine Chemistry: Summarizes the compounds found in wine, their basic chemical properties and their contribution to wine stability and sensory properties Focuses on chemical and biochemical reaction mechanisms that are critical to wine production processes such as fermentation, aging, physiochemical separations and additions Includes case studies showing how chemistry can be harnessed to enhance wine color, aroma, flavor, balance, stability and quality. This descriptive text provides an overview of wine components and explains the key chemical reactions they undergo, such as those controlling the transformation of grape components, those that arise during fermentation, and the evolution of wine flavor and color. The book aims to guide the reader, who perhaps only has a basic knowledge of chemistry, to rationally explain or predict the outcomes of chemical reactions that contribute to the diversity observed among wines. This will help students, winemakers and other interested individuals to anticipate the effects of wine treatments and processes, or interpret experimental results based on an understanding of the major chemical reactions that can occur in wine.
Open Access
Spatiotemporal changes in the accumulation of sugar and potassium within individual 'Sauvignon Blanc' (Vitis vinifera L.) berries
(Julius Kühn-Institut, 2017) Coetzee, Z.A.; Walker, R.R.; Deloire, A.; Clarke, S.J.; Barril, C.; Rogiers, S.Y.
It has been speculated that there may be a link between the transport of sugar and potassium into grape berries during ripening as they exhibit similar accumulation patterns. It is unclear if this proposed link is apparent in individual grape berries and in the grape berry compartments. Single grape berries were therefore analysed for sugar and potassium content and concentration within the skin, seeds and the pulp from pre-véraison until harvest. Sugar and potassium had similar accumulation patterns and positive relationships were confirmed between the sugar and potassium content within individual berries and compartments. The sugar content in the grape berry, however, increased 5-fold during ripening whereas the potassium content only doubled. Both sugar and potassium increased with berry size, suggesting a ternary relationship with berry water. The high variability in sugar and potassium contents between berries however affirms plasticity in their accumulation within individual berries.
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Impact of bottle aging on smoke-tainted wines from different grape cultivars
(ACS Publications, 2017) Ristic, R.; van der Hulst, L.; Capone, D.; Wilkinson, K.
Smoke taint is the term given to the objectionable smoky, medicinal, and ashy characters that can be exhibited in wines following vineyard exposure to bushfire smoke. This study sought to investigate the stability of smoke taint by determining changes in the composition and sensory properties of wines following 5 to 6 years of bottle aging. Small increases in guaiacol and 4-methylguaiacol (of up to 6 μg/L) were observed after bottle aging of smoke-affected red and white wines, while syringol increased by as much as 29 μg/L. However, increased volatile phenol levels were also observed in control red wines, which indicated that changes in the composition of smoke-affected wines were due to acid hydrolysis of conjugate forms of both naturally occurring and smoke-derived volatile phenols. Acid hydrolysis of smoke-affected wines (post-bottle aging) released additional quantities of volatile phenols, which demonstrated the relative stability of glycoconjugate precursors to the mildly acidic conditions of wine. Bottle aging affected the sensory profiles of smoke-affected wines in different ways. Diminished fruit aroma and flavor led to the intensification of smoke taint in some wines, but smoke-related sensory attributes became less apparent in smoke-affected Shiraz wines, post-bottle aging.
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Use of winemaking supplements to modify the composition and sensory properties of Shiraz wine
(American Chemical Society, 2017) Li, S.; Bindon, K.; Bastian, S.; Jiranek, V.; Wilkinson, K.
Wine quality can be significantly impacted by tannin and polysaccharide composition, which can in turn be influenced by grape maturity and winemaking practices. This study explored the impact of three commercial wine additives, a maceration enzyme, an oenotannin and a mannoprotein, on the composition and sensory properties of red wine; in particular, in mimicking the mouthfeel associated with wines made from riper grapes. Shiraz grapes were harvested at 24 and 28 °Brix and the former vinified with commercial additives introduced either individually or in combination. Compositional analyses of finished wines included tannin and polysaccharide concentration, composition and size distribution by high performance liquid chromatography, while the sensory profiles of wines were assessed by descriptive analysis. As expected, wines made from riper grapes were naturally higher in tannin and mannoprotein than wines made from grapes harvested earlier. Enzyme addition resulted in a significantly higher concentration and average molecular mass of wine tannin, which increased wine astringency. Conversely, mannoprotein addition reduced tannin concentration and astringency. Addition of oenotannin did not meaningfully influence wine composition or sensory properties.
Open Access
The evolution of Lachancea thermotolerans is driven by geographical determination, anthropisation and flux between different ecosystems
(Public Library Science, 2017) Hranilovic, A.; Bely, M.; Masneuf-Pomarede, I.; Jiranek, V.; Albertin, W.; Fairhead, C.
The yeast Lachancea thermotolerans (formerly Kluyveromyces thermotolerans) is a species with remarkable, yet underexplored, biotechnological potential. This ubiquist occupies a range of natural and anthropic habitats covering a wide geographic span. To gain an insight into L. thermotolerans population diversity and structure, 172 isolates sourced from diverse habitats worldwide were analysed using a set of 14 microsatellite markers. The resultant clustering revealed that the evolution of L. thermotolerans has been driven by the geography and ecological niche of the isolation sources. Isolates originating from anthropic environments, in particular grapes and wine, were genetically close, thus suggesting domestication events within the species. The observed clustering was further validated by several means including, population structure analysis, F-statistics, Mantel's test and the analysis of molecular variance (AMOVA). Phenotypic performance of isolates was tested using several growth substrates and physicochemical conditions, providing added support for the clustering. Altogether, this study sheds light on the genotypic and phenotypic diversity of L. thermotolerans, contributing to a better understanding of the population structure, ecology and evolution of this non-Saccharomyces yeast.
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Factors affecting extraction and evolution of phenolic compounds during red wine maceration and the role of process modelling
(Elsevier, 2017) Setford, P.; Jeffery, D.; Grbin, P.; Muhlack, R.
Background, The overall quality of red wine is well known to be influenced markedly by various phenolic compounds that are extracted from the grape solids during maceration. The concentration and composition of phenolics then impact the flavour and mouthfeel of wines. Scope and Approach, This review analyses the available literature on specific process variables that influence the diffusive mass transfer and evolution of phenolic compounds during red wine maceration. These variables are discussed in terms of techniques and strategies used by winemakers to influence the extractive behaviour of phenolic compounds and control their concentration in the finished wine. Mathematical models used to describe extraction and evolution phenomena in wine are also examined and the potential for future models to predict phenolic behaviour is discussed. Key Findings and Conclusions, The impact of various winemaking techniques aimed at improving the extraction of phenolic compounds during red winemaking, as well as the subsequent reactions that take place following extraction, are qualitatively well understood. Mathematically, many of these techniques can be described in terms of their changing process variables such as temperature, solvent conditions and sold-liquid contact. Despite this, non-steady state models for mass transport or reaction kinetics of phenolic compounds in wine fermentation are currently unavailable in published literature. Further research into the production of global models capable of accurately describing this behaviour would be a significant advancement for industry and would aid in the development of adaptive process control technologies for red wine phenolic composition.
Open Access
Potassium in the grape (Vitis vinifera L.) berry: transport and function
(Frontiers Media SA, 2017) Rogiers, S.; Coetzee, Z.; Walker, R.; Deloire, A.; Tyerman, S.
K⁺ is the most abundant cation in the grape berry. Here we focus on the most recent information in the long distance transport and partitioning of K⁺ within the grapevine and postulate on the potential role of K⁺ in berry sugar accumulation, berry water relations, cellular growth, disease resistance, abiotic stress tolerance and mitigating senescence. By integrating information from several different plant systems we have been able to generate new hypotheses on the integral functions of this predominant cation and to improve our understanding of how these functions contribute to grape berry growth and ripening. Valuable contributions to the study of K⁺ in membrane stabilization, turgor maintenance and phloem transport have allowed us to propose a mechanistic model for the role of this cation in grape berry development.
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Impact of reduced atmospheric CO₂ and varied potassium supply on carbohydrate and potassium distribution in grapevine and grape berries (Vitis vinifera L.)
(Elsevier Masson SAS, 2017) Coetzee, Z.; Walker, R.; Deloire, A.; Barril, C.; Clarke, S.; Rogiers, S.
To assess the robustness of the apparent sugar-potassium relationship during ripening of grape berries, a controlled-environment study was conducted on Shiraz vines involving ambient and reduced (by 34%) atmospheric CO₂ concentrations, and standard and increased (by 67%) soil potassium applications from prior to the onset of ripening. The leaf net photoassimilation rate was decreased by 35% in the reduced CO₂ treatment. The reduction in CO₂ delayed the onset of ripening, but at harvest the sugar content of the berry pericarp was similar to that of plants grown in ambient conditions. The potassium content of the berry pericarp in the reduced CO₂ treatment was however higher than for the ambient CO₂. Berry potassium, sugar and water content were strongly correlated, regardless of treatments, alluding to a ternary link during ripening. Root starch content was lower under reduced CO₂ conditions, and therefore likely acted as a source of carbohydrates during berry ripening. Root carbohydrate reserve replenishment could also have been moderated under reduced CO₂ at the expense of berry ripening. Given that root potassium concentration was less in the vines grown in the low CO₂ atmosphere, these results point toward whole-plant fine-tuning of carbohydrate and potassium partitioning aimed at optimising fruit ripening.
Open Access
Hypoxia in grape berries: the role of seed respiration and lenticels on the berry pedicel and the possible link to cell death
(Oxford University Press, 2018) Xiao, Z.; Rogiers, S.; Sadras, V.; Tyerman, S.D.
Mesocarp cell death (CD) during ripening is common in berries of seeded Vitis vinifera L wine cultivars. We examined if hypoxia within berries is linked to CD. Internal oxygen concentration ([O₂]) across the mesocarp was measured in berries from Chardonnay and Shiraz, both seeded, and Ruby Seedless, using an oxygen micro-sensor. Steep [O₂] gradients were observed across the skin and [O₂] decreased toward the middle of the mesocarp. As ripening progressed the minimum [O₂] approached zero in the seeded cultivars and correlated to the profile of CD across the mesocarp. Seed respiration declined during ripening, from a large proportion of total berry respiration early to negligible at latter stages. [O₂] increased towards the central axis corresponding to the presence of air spaces visualised using x-ray micro-CT. These air spaces connect to the pedicel where lenticels are located that are critical for berry O₂ uptake as a function of temperature, and when blocked caused hypoxia in Chardonnay berries, ethanol accumulation and CD. The implications of hypoxia in grape berries are discussed in terms of its role in CD, ripening and berry water relations.
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Sustainable wineries through waste valorisation: A review of grape marc utilisation for value-added products
(Elsevier, 2018) Muhlack, R.; Potumarthi, R.; Jeffery, D.
Grapes are one of the most cultivated fruits worldwide, with one third of total production used in winemaking. Both red and white winemaking processes result in substantial quantities of solid organic waste, such as grape marc (pomace) and stalks, which requires suitable disposal. Grape marc accounts for approximately 10-30% of the mass of grapes crushed and contains unfermented sugars, alcohol, polyphenols, tannins, pigments, and other valuable products. Being a natural plant product rich in lignocellulosic compounds, grape marc is also a promising feedstock for renewable energy production. However, despite grape marc having such potential, advanced technologies to exploit this have not been widely adopted in wineries and allied industries. This review covers opportunities beyond traditional composting and animal feed, and examines value-added uses via the extraction of useful components from grape marc, as well as thermochemical and biological treatments for energy recovery, fuel or beverage alcohol production, and specialty novel products and applications such as biosurfactants and environmental remediation. New advances in relevant technology for each of these processes are discussed, and future directions proposed at both individual producer and regional facility scales, including advanced processing techniques for integrated ethanol production followed by bioenergy generation from the spent marc.
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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
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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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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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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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