Browsing by Author "MacNamara, K."

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    Flavour components of whiskey. I. distribution and recovery of compounds by fractional vacuum distillation
    (South African Society for Enology and Viticulture, 2001) MacNamara, K.; Van Wyk, C. J.; Augustyn, O. P. H.; Rapp, A.
    A 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.
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    Flavour components of whiskey. II. ageing changes in the high-volatility fraction
    (South African Society for Enology and Viticulture, 2001) MacNamara, K.; Van Wyk, C. J.; Augustyn, O. P. H.; Rapp, A.
    The 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.
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    Flavour components of whiskey. III. ageing changes in the low-volatility fraction
    (South African Society for Enology and Viticulture, 2001) MacNamara, K.; Van Wyk, C. J.; Brunerie, P.; Augustyn, O. P. H.; Rapp, A.
    The low-volatility wood-originating compounds isolated from whiskey by vacuum fractional distillation were analysed by high-resolution gas chromatography and mass spectrometry (GC-MS). Three phenolic esters previously unreported in whiskey were identified and confirmed by synthesis. Formation profiles for sixteen compounds were established in whiskeys aged for periods from 1.5 to 10 years in second-fill heavy-charred American Bourbon barrels. These profiles indicated significant increases for several compounds, especially in the older whiskeys. Ratios of aromatic phenolic aldehydes, and similar ratio changes during ageing, were different from reported data relating to other wood types and treatments. Further preparative separation by high-pressure liquid chromatography (HPLC) of the wood fraction followed by GC-MS allowed retention and mass spectral characterisation of additional compounds originating from wood. Sensory investigation indicated different and unique contributions from the HPLC cuts. Spiking of the three phenolic esters into a young whiskey gave a detectable increase in maturation intensity.