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Item Open Access Wine consumers' subjective responses to wine mouthfeel and understanding of wine body(Elsevier BV, 2017) Niimi, J.; Danner, L.; Li, L.; Bossan, H.; Bastian, S.E.P.Abstract not availableItem Metadata only Emerging trends in the application of malolactic fermentation(Wiley-Blackwell, 2015) Bartowsky, E.; Costello, P.; Chambers, P.Deacidification of wines by malolactic fermentation (MLF) is an essential step in the production of most red, many white and some sparkling base wines. While this secondary fermentation can occur spontaneously, the majority of winemakers, particularly in new world winemaking regions, prefer to minimise the risk of a failed or sluggish MLF by inoculating with a reliable, commercially available starter culture. This review focuses on the scientific literature underpinning growing trends in the application of MLF starters. It considers the literature on co-inoculation regimes, where MLF bacteria are inoculated into a ferment prior to completion of alcoholic fermentation and what benefits this might bring relative to sequential inoculation, when bacteria are added after completion of primary fermentation. It also considers the benefits of the growing trend of using bacteria other than the traditional Oenococcus oeni for induction of MLF, and of developing starter cultures from regional isolates of MLF bacteria to enhance regional identity of wines.Item Metadata only The grapevine: from the science to the practice of growing vines for wine(Patrick Iland Wine Promotions, 2011) Iland, P.; Dry, P.; Proffitt, T.; Tyerman, S.The Grapevine explores the links between the scientific principles and the practice of viticulture.Item Metadata only Effect of increased irrigation and additional nitrogen fertilisation on the concentration of green aroma compounds in Vitis vinifera L. Merlot fruit and wine(Wiley, 2014) Mendez-Costabel, M.; Wilkinson, K.; Bastian, S.; Jordans, C.; McCarthy, M.; Ford, C.; Dokoozlian, K.Background and Aims: Green aroma compounds are considered undesirable when present at a high concentration in red wines. This study aimed to understand the effect of two irrigation levels and a higher than standard nitrogen fertilisation on the concentration of both 3-isobutyl-2-methoxypyrazine (IBMP) and six C6 compounds during fruit development. Methods and Results: Fruit samples were collected biweekly during the 2009 and 2010 seasons in a commercial Vitis vinifera L. Merlot vineyard in California, USA, where two irrigation levels (70 and 100% of crop evapotranspiration) and a higher than standard nitrogen fertilisation dose were implemented. The higher irrigation level and additional nitrogen promoted canopy growth and decreased fruit exposure, resulting in increased concentration of IBMP during fruit maturation. The concentration of the six measured C6 compounds, however, was not affected. Deficit irrigation increased fruit colour, quercetin glycosides and phenol-free glucose glycosides (i.e. aroma precursors), and decreased vine yield. The two irrigation levels did not differ on the sensory vegetal perception of the wines, but the additional application of nitrogen fertiliser at fruitset enhanced it. Significance of the Study: These findings confirm previous work showing that vineyard management practices influence fruit and wine concentration of IBMP, and demonstrate for the first time that the same practices have no significant impact on the concentration of six C6 compounds in grapes or on the concentration of hexanol in wines. Grapegrowers aiming to minimise IBMP concentration in fruit at harvest would probably benefit from a reduced application of water and nitrogen to the vineyard.Item Metadata only Effect of winter rainfall on yield components and fruit green aromas of Vitis vinifera L. cv. Merlot in California(Wiley, 2014) Mendez-Costabel, M.; Wilkinson, K.; Bastian, S.; Jordans, C.; McCarthy, M.; Ford, C.; Dokoozlian, N.impact of winter rainfall on the main compounds responsible for green aromas in grapes and wines, 3-isobutyl-2-methoxypyrazine (IBMP) and C6 compounds. These compounds are considered undesirable in grapes and wines above the threshold concentration. Methods and Results: One treatment subjected vines to average rainfall, while the other excluded winter rainfall by covering the ground with a plastic tarpaulin during the entire dormant season (November to mid-March). Irrigation for both treatments was maintained at a weekly rate of 70% of crop evapotranspiration until commercial harvest. Canopy growth, berry size and vine yield were significantly reduced by rainfall exclusion, and a significant increase in the fruit to pruning mass ratio was recorded from one season to another. Synthesis of IBMP was significantly greater in vines under normal rainfall, whereas C6 compounds were significantly different between treatments only at the end of the second season. Fruit and wine composition, mainly colour and mouthfeel compounds, were positively affected by the absence of rainfall in both years. Wine descriptive analysis showed that the lack of rainfall produced wines perceived as less green and of more intense fruit attributes in the first season. As a consequence of the reduction in vine growth, however, the same treatment produced wines less intense in fruit aromas and of inferior tannin quality in the following season. Conclusions: These results show that the soil moisture level prior to budbreak affects both canopy growth and vine yield, even when irrigation is applied following budbreak. If the rainfall level is below normal, the positive effect on fruit and wine composition achieved through smaller berry size may be offset by a significant reduction in canopy growth, resulting in severely unbalanced vines, i.e. inadequate fruit to pruning mass ratio. Significance of the Study: Growers aiming to minimise the level of IBMP at harvest would benefit from applying moderate deficit irrigation and nitrogen fertilisation rates and also might achieve an earlier harvest date for those vineyards where the absence of undesirable vegetal characters is considered a key harvest metric.Item Metadata only Ester synthesis and hydrolysis in an aqueous environment, and strain specific changes during malolactic fermentation in wine with Oenococcus oeni(Elsevier Sci Ltd, 2013) Sumby, K.; Jiranek, V.; Grbin, P.Previous work has shown that Oenococcus oeni produces esterases that are capable of hydrolysing artificial substrates. Using SPME-GCMS, this study provides evidence that purified O. oeni esterases have the ability to both synthesise and hydrolyse esters. Two purified esterases (EstA2 and EstB28) synthesised ethyl butanoate and ethyl hexanoate to varying degrees. Both purified esterases hydrolysed ethyl butanoate, ethyl hexanoate and ethyl octanoate. Once this dual activity was confirmed, malolactic fermentation (MLF) trials were conducted in wine with O. oeni strains that had been previously observed to have either high or low esterase activity against artificial substrates. Strain specific differences were observed and strains with low esterase hydrolysis activity against artificial substrates had a higher level of total esters measured after MLF. The results demonstrate the impact that O. oeni has on wine aroma and relates this to the ester hydrolysis and synthesis abilities of O. oeni strains.Item Metadata only Effect of ammonium nitrogen supplementation of grape juice on wine volatiles and non-volatiles composition of the aromatic grape variety Albariño(Elsevier Sci Ltd, 2012) Vilanova, M.; Siebert, T.; Varela, C.; Pretorius, I.; Henschke, P.Vitis vinifera cv. Albariño is an aromatic variety characterised by terpenes present largely as glycosidic flavour precursor compounds, which depends on fermentation to reveal its aromatic varietal potential. Clarified Albariño must containing 250mgN/L (control) was supplemented with diammonium phosphate to 350 and 450mgN/L before fermentation with a high-nitrogen-demand wine strain of Saccharomyces cerevisiae (M05). Ammonium supplementation had a significant effect on the chemical composition (titratable acidity and ethanol) and volatile profile of Albariño wines. Varietal compounds in the free fraction (limonene, linalool, α-terpineol, α-ionone and β-damascenone) and bound (limonene, linalool and α-terpineol), as well as most yeast-derived fermentation products (including esters, higher alcohols and volatile acids) were associated with moderate nitrogen concentrations. Free β-ionone, bound geraniol, bound α-ionone, bound β-damascenone and 1-hexanol were associated with high nitrogen concentrations. OAV wines made with moderate nitrogen exhibited a higher total odorant activity, driven by ethyl esters, terpenes and Câ â -norisoprenoids, resulting in fruity and floral aroma attributes.Item Metadata only Comparative genomics: a revolutionary tool for wine yeast strain development(Current Biology Ltd, 2013) Borneman, A.; Pretorius, I.; Chambers, P.The application of Next Generation sequencing to comparative genomics is enabling in-depth characterization of genetic variation between wine yeast strains used in fermentation starter cultures. Knowledge from this work will be harnessed in strain development programs. As a result, winemakers will soon have at their disposal novel, improved yeast starter cultures displaying increased reliability and providing a means of tailoring wine sensory characteristics for new and ever-changing markets.Item Metadata only Flavour-active wine yeasts(Springer-Verlag, 2012) Cordente, A.; Curtin, C.; Varela, C.; Pretorius, I.The flavour of fermented beverages such as beer, cider, saké and wine owe much to the primary fermentation yeast used in their production, Saccharomyces cerevisiae. Where once the role of yeast in fermented beverage flavour was thought to be limited to a small number of volatile esters and higher alcohols, the discovery that wine yeast release highly potent sulfur compounds from non-volatile precursors found in grapes has driven researchers to look more closely at how choice of yeast can influence wine style. This review explores recent progress towards understanding the range of ‘flavour phenotypes’ that wine yeast exhibit, and how this knowledge has been used to develop novel flavour-active yeasts. In addition, emerging opportunities to augment these phenotypes by engineering yeast to produce so-called grape varietal compounds, such as monoterpenoids, will be discussed.Item Metadata only Evaluation of gene modification strategies for the development of low-alcohol-wine yeasts(Amer Soc Microbiology, 2012) Varela, C.; Kutyna, D.; Solomon, M.; Black, C.; Borneman, A.; Henschke, P.; Pretorius, I.; Chambers, P.Saccharomyces cerevisiae has evolved a highly efficient strategy for energy generation which maximizes ATP energy production from sugar. This adaptation enables efficient energy generation under anaerobic conditions and limits competition from other microorganisms by producing toxic metabolites, such as ethanol and CO(2). Yeast fermentative and flavor capacity forms the biotechnological basis of a wide range of alcohol-containing beverages. Largely as a result of consumer demand for improved flavor, the alcohol content of some beverages like wine has increased. However, a global trend has recently emerged toward lowering the ethanol content of alcoholic beverages. One option for decreasing ethanol concentration is to use yeast strains able to divert some carbon away from ethanol production. In the case of wine, we have generated and evaluated a large number of gene modifications that were predicted, or known, to impact ethanol formation. Using the same yeast genetic background, 41 modifications were assessed. Enhancing glycerol production by increasing expression of the glyceraldehyde-3-phosphate dehydrogenase gene, GPD1, was the most efficient strategy to lower ethanol concentration. However, additional modifications were needed to avoid negatively affecting wine quality. Two strains carrying several stable, chromosomally integrated modifications showed significantly lower ethanol production in fermenting grape juice. Strain AWRI2531 was able to decrease ethanol concentrations from 15.6% (vol/vol) to 13.2% (vol/vol), whereas AWRI2532 lowered ethanol content from 15.6% (vol/vol) to 12% (vol/vol) in both Chardonnay and Cabernet Sauvignon juices. Both strains, however, produced high concentrations of acetaldehyde and acetoin, which negatively affect wine flavor. Further modifications of these strains allowed reduction of these metabolites.Item Metadata only Di-tert-butyl (2R,3R)-2-{[(2E)-3-(4-acetyloxy-3-methoxyphenyl)prop-2-enoyl]-oxy}-3-hydroxybutanedioate(Blackwell Munksgaard, 2012) Hixson, J.; Taylor, D.; Ng, S.; Tiekink, E.In the title molecule, C₂₄H₃₂O₁₀, one tert-butyl ester group is folded towards the central benzene ring while the other is directed away. The acetyl group is almost perpendicular to the benzene ring to which it is connected [C-C-O-C torsion angle = 90.4 (12)°]. The conformation about the ethene bond [1.313(7)Å] is E. The atoms of the benzene ring and its attached ester group and part of the hydroxy tert-butyl ester side chain are disordered over two sets of sites in a 50:50 ratio. Linear supramolecular chains along the a axis mediated by hydroxy-carbonyl O-H...O hydrogen bonds feature in the crystal packing. The same H atom also partakes in an intramolecular O-H...O interaction.Item Metadata only 1,4-Di-tert-butyl (2R,3R)-2-({(2E)-3-[4(acetyloxy)phenyl]prop-2-enoyl}oxy)-3hydroxybutanedioate(Blackwell Munksgaard, 2012) Hixson, J.; Taylor, D.; Ng, S.; Tiekink, E.The title compound, C₂₃H3₃₀O₉, has an approximate T-shape with the tert-butyl ester groups lying either side of the benzene ring. The acetyl group is almost perpendicular to the benzene ring to which it is connected [C-C-O-C torsion angle = -106.7 (3)°]. The conformation about the C=C double bond [1.331 (4) Å] is E. Linear supramolecular chains along the a axis mediated by hydroxy-carbonyl O-H...O hydrogen bonds feature in the crystal packing. The same H atom is also involved in an intramolecular O-H...O interaction.Item Metadata only Effects on 3-mercaptohexan-1-ol precursor concentrations from prolonged storage of Sauvignon blanc grapes prior to crushing and pressing(Amer Chemical Soc, 2012) Capone, D.; Black, C.; Jeffery, D.Formation of wine thiol precursors is a dynamic process, which can be influenced by vineyard and winery processing operations. With the aim of increasing thiol precursor concentrations, a study of the effects of storing machine-harvested Sauvignon blanc grapes prior to crushing and pressing was undertaken on a commercial scale. 3-Mercaptohexan-1-ol (3-MH) precursors, 2-S-glutathionylcaftaric acid (grape reaction product, GRP), glutathione (GSH) and a number of C6 compounds were assessed at several time points during the experiment. The concentration of the cysteine precursor to 3-MH doubled within 8 h and tripled after 30 h while the GSH and cysteinylglycine precursors increased in concentration roughly 1.5 times. (E)-2-Hexenal and GSH levels decreased as thiol precursors, GRP and C6 alcohols increased during storage. Principal component analysis revealed that precursors contributed to most of the variation within the samples over the storage period, with additional influence, primarily from GSH and GRP, as well as (E)-2-hexenal and (Z)-3-hexen-1-ol. Early storage time points were associated with higher concentrations of GSH and some unsaturated C6 compounds while longer storage times were most closely associated with higher thiol precursor and GRP concentrations. This study provides a detailed overview of interactions related to thiol precursor formation on a commercial scale and highlights the ability to manipulate precursor concentrations prior to grape crushing.Item Metadata only Yeast strain-derived sensory differences retained in Sauvignon blanc wines after extended bottle storage(Amer Soc Enology Viticulture, 2011) King, E.; Francis, I.; Swiegers, J.; Curtin, C.Fermentations using different yeast strains can result in varying concentrations of volatile thiols and substantial sensory effects in young Sauvignon blanc wines. These yeast-derived aroma differences are generally thought to be short lived; therefore, Sauvignon blanc wines made using different yeast strains in two separate studies were investigated after three years of cellar storage. Differences were observed in the volatile composition and sensory profiles of the three-year-old wines that, when compared with the six-month data, demonstrated the continued influence of yeast strains. This observation provides further evidence that choice of yeast strain is important to wine flavor.Item Metadata only Rapid isolation of red wine polymeric polyphenols by solid-phase extraction(Amer Chemical Soc, 2008) Jeffery, D.; Mercurio, M.; Herderich, M.; Hayasaka, Y.; Smith, P.A rapid technique for the isolation of polymeric polyphenols from red wine has been developed and validated. A copolymer reversed-phase SPE cartridge was utilized in conjunction with predominantly organic eluents to provide three phenolic fractions from red wine without the need for sample pretreatment. The first fraction contained the bulk of the monomeric and oligomeric phenolic material, while the second and third fractions contained the polymeric polyphenolic compounds, as determined by HPLC analysis. The two polymeric polyphenolic fractions differed in their solubility and extent of pigmentation, and the differences appeared to be related to wine age. This method contrasted with other available fractionation techniques because the interfering, nonpolymeric material can be removed in a single wash fraction, while the polymeric material is separated into two distinct fractions based on their diverse physicochemical properties. It is anticipated that the rapid access to discrete polymeric fractions afforded by this method will be of benefit in furthering the understanding of red wine polymeric polyphenols.Item Metadata only Synthesis of the putative structure of tridachiahydropyrone(Amer Chemical Soc, 2005) Jeffery, D.; Perkins, M.; White, J.[reaction: see text] A short total synthesis of the putative structure of the marine natural product tridachiahydropyrone as a single enantiomer is described. Novel steps include a cuprate addition and cyclization to form a cyclohexanone ring and formation of the bicyclic pyrone with P(2)O(5) on Celite. The spectroscopic data obtained for compound 1 do not match those reported for tridachiahydropyrone; therefore, revision of the assigned natural product structure is warranted.Item Metadata only A method for mini-lot fermentation for use in research and commercial viticultural and winemaking trials(Ryan Publications, 2006) Holt, H.; Iland, P.; Ristic, R.Item Metadata only Chirality and its effect on wine aroma: recent experiences in aroma research at the Australian Wine Research Institute(Wine Publishers Pty Ltd, 2008) Elsey, G.; Brown, R.; Pardon, K.; Capone, D.; Sefton, M.; Herderich, M.; Pretorius, I.Item Metadata only Isolation of sulfite reductase variants of a commercial wine yeast with significantly reduced hydrogen sulfide production(Elsevier Science BV, 2009) Cordente, A.; Heinrich, A.; Pretorius, I.; Swiegers, J.The production of hydrogen sulfide (H(2)S) during fermentation is a common and significant problem in the global wine industry as it imparts undesirable off-flavors at low concentrations. The yeast Saccharomyces cerevisiae plays a crucial role in the production of volatile sulfur compounds in wine. In this respect, H(2)S is a necessary intermediate in the assimilation of sulfur by yeast through the sulfate reduction sequence with the key enzyme being sulfite reductase. In this study, we used a classical mutagenesis method to develop and isolate a series of strains, derived from a commercial diploid wine yeast (PDM), which showed a drastic reduction in H(2)S production in both synthetic and grape juice fermentations. Specific mutations in the MET10 and MET5 genes, which encode the catalytic alpha- and beta-subunits of the sulfite reductase enzyme, respectively, were identified in six of the isolated strains. Fermentations with these strains indicated that, in comparison with the parent strain, H(2)S production was reduced by 50-99%, depending on the strain. Further analysis of the wines made with the selected strains indicated that basic chemical parameters were similar to the parent strain except for total sulfite production, which was much higher in some of the mutant strains.Item Metadata only Odor detection thresholds and enantiomeric distributions of several 4-alkyl substituted γ-lactones in Australian red wine(Amer Chemical Soc, 2009) Cooke, R.; van Leeuwen, K.; Capone, D.; Gawel, R.; Elsey, G.; Sefton, M.The individual enantiomers of γ-octalactone (1), γ-nonalactone (2), γ-decalactone (3) and γ-dodecalactone (4) have been synthesized. The (R) series of enantiomers was prepared from l-glutamic acid by a strategy involving deamination and reduction to (S)-5-oxo-2-tetrahydrofurancarboxaldehyde (S)-7. The different length side chains were introduced by a series of Wittig reactions, varying in the choice of phosphorane used. Hydrogenation then gave the final γ-lactones 1−4. The (S) series of enantiomers was prepared in an analogous fashion beginning with d-glutamic acid. Aroma detection thresholds for all eight enantiomers were determined in a “bag in a box” dry red wine by the application of ASTM method E 679, employing a panel of 25 members. The lowest threshold determined was 8 μg/L for (R)-dodecalactone (4) while the highest threshold was 285 μg/L for (R)-nonalactone (2). With the exception of γ-decalactone (3) there were statistically significant differences (at the 5% level) in aroma detection thresholds between the two enantiomers of the same lactone. A stable isotope method developed for quantification of the lactones 1−4 has been extended for use with chiral phase GC (Rt-βDEXcst capillary column) allowing quantification of the individual enantiomers. The enantiomeric distribution of γ-octalactone (1) and γ-nonalactone (2) in seven botrytized wines and of 2 in a total of 34 red wines were thus determined; with few exceptions, the (R) enantiomer of γ-nonalactone (2) was found to be more prevalent than its (S) counterpart in the dry red and botrytized white wines analyzed. The same was true for γ-octalactone (1) in the botrytized white wines.