Initial Study on the Guava Aroma of Chenin Blanc and Colombar Wines

An initial study indicated the importance of mercaptan on the aroma of Colombar and Chenin blanc wines. A synthesized mercaptan viz. 4-methyl-4-mercapto-pentan-2-one when added to neutral wine effected a Colombar or Chenin blanc wine aroma. The importance of sulphur components on wine aroma is emphasized

Ruthenium oxide-carbon-based nanofiller-reinforced conducting polymer nanocomposites and their supercapacitor applications.

In this review article, we have presented for the first time the new applications of supercapacitor technologies and working principles of the family of RuO2-carbon-based nanofiller-reinforced conducting polymer nanocomposites. Our review focuses on pseudocapacitors and symmetric and asymmetric supercapacitors. Over the last years, the supercapacitors as a new technology in energy storage systems have attracted more and more attention. They have some unique characteristics such as fast charge/discharge capability, high energy and power densities, and long stability. However, the need for economic, compatible, and easy synthesis materials for supercapacitors have led to the development of RuO2-carbon-based nanofiller-reinforced conducting polymer nanocomposites with RuO2. Therefore, the aim of this manuscript was to review RuO2-carbon-based nanofiller-reinforced conducting polymer nanocomposites with RuO2 over the last 17 years

The self-organizing fractal theory as a universal discovery method: the phenomenon of life

A universal discovery method potentially applicable to all disciplines studying organizational phenomena has been developed. This method takes advantage of a new form of global symmetry, namely, scale-invariance of self-organizational dynamics of energy/matter at all levels of organizational hierarchy, from elementary particles through cells and organisms to the Universe as a whole. The method is based on an alternative conceptualization of physical reality postulating that the energy/matter comprising the Universe is far from equilibrium, that it exists as a flow, and that it develops via self-organization in accordance with the empirical laws of nonequilibrium thermodynamics. It is postulated that the energy/matter flowing through and comprising the Universe evolves as a multiscale, self-similar structure-process, i.e., as a self-organizing fractal. This means that certain organizational structures and processes are scale-invariant and are reproduced at all levels of the organizational hierarchy. Being a form of symmetry, scale-invariance naturally lends itself to a new discovery method that allows for the deduction of missing information by comparing scale-invariant organizational patterns across different levels of the organizational hierarchy

Analoe van retinol

Proefskrif (M. Sc.) -- Universiteit van Stellenbosch, 1969.Full text to be digitised and attached to bibliographic record

Yeast biodiversity in vineyards and wineries and its importance to the South African wine industry : a review

CITATION: Pretorius, I. S., Van Der Westhuizen, T. J. & Augustyn, O. P. H. 1999. Yeast biodiversity in vineyards and wineries and its importance to the South African wine industry. a review. South African Journal of Enology & Viticulture, 20(2):61-70, doi:10.21548/20-2-2234.The original publication is available at http://www.journals.ac.za/index.php/sajevThe art of winemaking is as old as human civilization and the use of yeast in this complex ecological and biochemical process dates back to ancient times. Traditionally, yeasts associated with grape berries were simply allowed to ferment the sugars to ethanol, carbon dioxide and other minor, but important, metabolites. Spontaneous fermentations are still being used in boutique wineries that depend more on vintage variability. Various microbes found on the surface of grape skins and the indigenous microbiota associated with winery surfaces participate in these natural wine fermentations. Yeasts of the genera Kloeckera, Hanseniaspora and Candida predominate in the early stages, followed by several species of Metschnikowia and Pichia (including those species that were previously assigned to the genus Hansenula) in the middle stages when the ethanol rises to 3-4%. The latter stages of natural wine fermentations are invariably dominated by the alcohol-tolerant strains of Saccharomyces cerevisiae. However, other yeasts, such as species of Brettanomyces, Kluyveromyces, Schizosaccharomyces, Torulaspora and Zygosaccharomyces also may be present during the fermentation and can occur in the resultant wine. By contrast, the rule, rather than the exception, for modern wineries depending on reliable fermentation and the production of wines with predictable quality, is the use of specially selected starter cultures of Saccharomyces. However, the use of such cultures may not necessarily prevent the growth and metabolic activity of indigenous, winery associated strains of S. cerevisiae or other wild yeasts such as Kloeckera apiculata, Hanseniaspora uvarum, Candida stellata and Torulaspora delbrueckii. It is therefore clear that both spontaneous and inoculated wine fermentations are affected by the diversity of yeasts associated with the vineyard (natural habitat) and winery (man-made niche). In light of this, focused taxonomic surveys within an ecological framework are essential to preserve and exploit the hidden oenological potential of the untapped wealth of yeast biodiversity in our wine-producing regions. To achieve this, yeast taxonomists need to continue to isolate and characterize new yeast species and strains, while wine microbiologists develop improved identification techniques that differentiate more efficiently among individual strains. At the same time such biological surveys will complement strain development and the current international effort of molecular biologists to assign a biological function to the products of each of the 6000 genes identified by computer analysis of the nucleotide sequence of the 16 chromosomes of a laboratory strain of S. cerevisiae. Furthermore, only when we have a much better understanding of yeast biodeversity, biogeography, ecology and the interaction within yeast communities will we be able to optimally harness gene technology that will benefit both the wine producer and the consumer.http://www.journals.ac.za/index.php/sajev/article/view/2234Publisher's versio

Flavour components of whiskey. II. ageing changes in the high-volatility fraction

CITATION: MacNamara, K., et al. 2001. Flavour components of whiskey. II. ageing changes in the high-volatility fraction. South African Journal of Enology & Viticulture, 22(2):75-81, doi:10.21548/22-2-2196.The original publication is available at http://www.journals.ac.za/index.php/sajevThe volatile compounds isolated from whiskey by fractional vacuum distillation were identified by two-dimensional capillary gas chromatography/mass spectrometry. Changing levels with ageing were quantified for the most abundant compounds by direct split injection of whiskeys on a gas chromatograph equipped with a flame ionisation detector. The ageing decreases in volatile sulfides were similarly determined using a sulfur chemiluminescence detector. Large volume headspace injection sufficiently reproduced the distillation enrichment to allow direct twodimensional determination of similar ageing changes for other trace compounds. Seven compounds at μg/L and low mg/L levels were monitored and quantified.http://www.journals.ac.za/index.php/sajev/article/view/2196Publisher's versio

Geographical distribution of indigenous saccharomyces cerevisiae strains isolated from vineyards in the coastal regions of the Western Cape in South Africa

CITATION: Van der Westhuizen, T. J., Augustyn, O. P. H. & Pretorius, I. S. 2000. Geographical distribution of indigenous saccharomyces cerevisiae strains isolated from vineyards in the coastal regions of the Western Cape in South Africa. South African Journal of Enology & Viticulture, 21(1):3-9, doi:10.21548/21-1-2179.The original publication is available at http://www.journals.ac.za/index.php/sajevNotwithstanding numerous studies on the yeast biota of grapes and grape must, the origin of the primary wine yeast Saccharomyces cerevisiae has been rather controversial. One school of thought claims that the primary source of S. cerevisiae is the vineyard, whereas another believes that ecological evidence points to a strict association with artificial, man-made environments such as wineries and fermentation plants. One of the main thrusts of these kinds of investigations is to understand the succession of yeasts during fermentation of wine and to determine the actual contribution of indigenous strains of S. cerevisiae and wild yeast species to the overall sensorial quality of the end product, even in guided fermentations using selected S. cerevisiae starter cultures. There is increasing interest within the wine community in the use of indigenous strains of S. cerevisiae and mixed starter cultures, tailored to reflect the characteristics of a given region. Against this background we have launched a comprehensive and long overdue biogeographical survey systematically cataloging yeasts in different climatic zones of the 350-year-old wine-producing regions of the Western Cape. The present paper represents the first phase of this programme aimed at preserving and exploiting the hidden oenological potential of the untapped yeast biodiversity in South Africa's primary grape-growing areas. Grapes were aseptically harvested from 13 sites in five areas in the coastal regions of the Western Cape. After fermentation, 30 yeast colonies per sample were isolated and examined for the presence of S. cerevisiae. Five sampling sites yielded no S. cerevisiae. CHEF-DNA analysis revealed the presence of 46 unique karyotypes in eight of the remaining sites. No dominant strain was identified and each site had its own unique collection of strains. The number of strains per site varied from two to 15. Only in four cases did one strain appear at two sites, while only one instance of a strain occurring at three sites was recorded. All sites contained killer and sensitive strains; however, killer strains did not always dominate. Commercial strains were recovered from three sites. Although commercial yeasts dominated the microflora at two sites, it appears that fears of commercial yeasts ultimately dominating the natural microflora seem to be exaggerated.http://www.journals.ac.za/index.php/sajev/article/view/2179Publisher's versio

Flavour components of whiskey. I. distribution and recovery of compounds by fractional vacuum distillation

CITATION: MacNamara, K., et al. 2001. Flavour components of whiskey. I. distribution and recovery of compounds by fractional vacuum distillation. South African Journal of Enology & Viticulture, 22(2):69-74, doi:10.21548/22-2-2194.The original publication is available at http://www.journals.ac.za/index.php/sajevA vacuum fractional distillation procedure is described for separating both the matrix components and flavour compounds of a whiskey into well-defined groups based on differences in azeotropic boiling points. The distillation was carried out at near ambient temperatures to accommodate both unaged and aged whiskies. Analytical and sensory data indicated good recovery of congeners. Individual fractions were reconstituted with ethanol and water to the original volume and strength dimensions of the whiskey. Undesirable thermal changes in the aged products were minimised by the low temperature fractionation and allowed changes in the flavour composition of whiskey due to maturation to be investigated for such unaged and aged reconstituted pairs.http://www.journals.ac.za/index.php/sajev/article/view/2194Publisher's versio

The value of long-chain fatty acid analysis, randomly amplified polymorphic DNA and electrophoretic karyotyping for the characterization of wine yeast strains

CITATION: Van Der Westhuizen, T. J., Augustyn, O. P. H., & Pretorius, I. S. 1998. The value of long-chain fatty acid analysis, randomly amplified polymorphic DNA and electrophoretic karyotyping for the characterization of wine yeast strains. South African Journal of Enology & Viticulture, 20(1):4-10, doi:10.21548/20-1-2219.The original publication is available at http://www.journals.ac.za/index.php/sajevWine yeast strains of Saccharomyces had previously been classified into several different species or varieties. This classification system was based mainly on sugar fermentation and assimilation patterns. Subsequently, most of these species were reclassified as Saccharomyces cerevisiae. The assignment of the majority of wine yeast strains to a single species does, however, not imply that all stains of S. cerevisiae are equally suitable for wine fermentation. These physiological strains of S. cerevisiae differ significantly in their fermentation performance and their ability to contribute to the final bouquet and quality of the various types of wine and distillates. Therefore, to ensure strain authenticity, security and proper strain management, it is of cardinal importance to have reliable taxonomic techniques available to identify and characterize individual strains of commercial cultures. In this study, 18 commercial wine yeast strains were characterized in order to evaluate and compare three taxonomic techniques, namely long-chain fatty acid analysis, randomly amplified polymorphic DNA (RAPD) and electrophoretic karyotyping. As a single identification technique, electrophoretic karyotyping seems to be the most useful method for routine fingerprinting of wine yeast strains. However, we propose that the combined use of these three techniques provides the most reliable means of differentiating amongst commercial wine yeast strains.http://www.journals.ac.za/index.php/sajev/article/view/2219Publisher's versio