Dungey K.A.,University of Adelaide |
Hayasaka Y.,Australian Wine Research Institute |
Wilkinson K.L.,University of Adelaide
Food Chemistry | Year: 2011
Guaiacol has been shown to accumulate in glycoconjugate forms in the fruit and leaves of grapevines following vineyard exposure to bushfire smoke. To investigate the glycosylation of guaiacol in smoke-affected grapes, a quantitative stable isotope dilution analysis method using liquid chromatography-tandem mass spectrometry was developed and validated, using the [2H4]-labelled analogue of guaiacol β-d- glucopyranoside as internal standard. The method was subsequently applied to the analysis of grapes sampled from grapevines exposed to either bushfire or experimental smoke, enabling compositional comparisons of guaiacol glycoconjugates in smoke-affected grapes from different varieties to be determined, for the first time. Guaiacol glucose-pentose disaccharide conjugates (i.e. glucosides with a terminal pentose) were found to be the most abundant glycoconjugate precursors present in smoke-affected grapes, regardless of grape variety or smoke source. Higher concentrations of glycoconjugates were measured in extracts of whole berry homogenate than juice. © 2010 Elsevier Ltd. All rights reserved.
McRae J.M.,Australian Wine Research Institute |
Kennedy J.A.,California State University, Fresno
Molecules | Year: 2011
Astringency is an important characteristic of red wine quality. The sensation is generally thought to be produced by the interaction of wine tannins with salivary proteins and the subsequent aggregation and precipitation of protein-tannin complexes. The importance of wine astringency for marketability has led to a wealth of research on the causes of astringency and how tannins impact the quality of the sensation, particularly with respect to tannin structure. Ultimately, the understanding of how tannin structure impacts astringency will allow the controlled manipulation of tannins via such methods as microoxygenation or fining to improve the quality of wines. © 2011.
Jolly N.P.,ARC Infruitec Nietvoorbij |
Varela C.,Australian Wine Research Institute |
Pretorius I.S.,Macquarie University
FEMS Yeast Research | Year: 2014
Saccharomyces cerevisiae and grape juice are 'natural companions' and make a happy wine marriage. However, this relationship can be enriched by allowing 'wild' non-Saccharomyces yeast to participate in a sequential manner in the early phases of grape must fermentation. However, such a triangular relationship is complex and can only be taken to 'the next level' if there are no spoilage yeast present and if the 'wine yeast' - S. cerevisiae - is able to exert its dominance in time to successfully complete the alcoholic fermentation. Winemakers apply various 'matchmaking' strategies (e.g. cellar hygiene, pH, SO2, temperature and nutrient management) to keep 'spoilers' (e.g. Dekkera bruxellensis) at bay, and allow 'compatible' wild yeast (e.g. Torulaspora delbrueckii, Pichia kluyveri, Lachancea thermotolerans and Candida/Metschnikowia pulcherrima) to harmonize with potent S. cerevisiae wine yeast and bring the best out in wine. Mismatching can lead to a 'two is company, three is a crowd' scenario. More than 40 of the 1500 known yeast species have been isolated from grape must. In this article, we review the specific flavour-active characteristics of those non-Saccharomyces species that might play a positive role in both spontaneous and inoculated wine ferments. We seek to present 'single-species' and 'multi-species' ferments in a new light and a new context, and we raise important questions about the direction of mixed-fermentation research to address market trends regarding so-called 'natural' wines. This review also highlights that, despite the fact that most frontier research and technological developments are often focussed primarily on S. cerevisiae, non-Saccharomyces research can benefit from the techniques and knowledge developed by research on the former. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.
Bindon K.A.,Australian Wine Research Institute |
Kennedy J.A.,Australian Wine Research Institute |
Kennedy J.A.,California State University, Fresno
Journal of Agricultural and Food Chemistry | Year: 2011
Proanthocyanidins were isolated from the skins of Cabernet Sauvignon grapes at different stages of grape development in order to study the effect of proanthocyanidin modification on the interaction with grape cell wall material. After veraison, the degree of proanthocyanidin polymerization increased, and thereafter was variable between 24 and 33 subunits as ripening progressed. Affinity of skin cell wall material for proanthocyanidin decreased with proanthocyanidin ripeness following veraison. A significant negative relationship (R 2 = 0.93) was found for average proanthocyanidin molecular mass and the proportion of high molecular mass proanthocyanidin adsorbed by skin cell wall material. This indicated that as proanthocyanidin polymerization increased, the affinity of a component of high molecular mass proanthocyanidins for skin cell wall material declined. This phenomenon was only associated with skin proanthocyanidins from colored grapes, as high molecular mass proanthocyanidins of equivalent subunit composition from colorless mutant Cabernet Sauvignon grapes had a higher affinity for skin cell wall material. © 2011 American Chemical Society.
Borneman A.R.,Australian Wine Research Institute |
Pretorius I.S.,University of South Australia |
Chambers P.J.,Australian Wine Research Institute
Current Opinion in Biotechnology | Year: 2013
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. © 2012 Elsevier Ltd.