Browsing by Author "Hurley, E. Kenneth"

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    Acid and Volatiles of Commercially-Available Lambic Beers
    Thompson Witrick, Katherine; Duncan, Susan E.; Hurley, E. Kenneth; O'Keefe, Sean F. (MDPI, 2017-10-26)
    Lambic beer is the oldest style of beer still being produced in the Western world using spontaneous fermentation. Gueuze is a style of lambic beer prepared by mixing young (one year) and older (two to three years) beers. Little is known about the volatiles and semi-volatiles found in commercial samples of gueuze lambic beers. SPME was used to extract the volatiles from nine different brands of lambic beer. GC-MS was used for the separation and identification of the compounds extracted with SPME. The pH and color were measured using standard procedures. A total of 50 compounds were identified in the nine brands. Seventeen of the 50 compounds identified have been previously identified. The compounds identified included a number of different chemical groups such as acids, alcohols, phenols, ketones, aldehydes, and esters. Ethyl acetate, 4-ethylphenol, and 4-ethylguaiacol are known by-products of the yeast, Brettanomyces, which is normally a spoilage microorganism in beer and wine, but important for the flavor characteristics of lambic beer. There were no differences in pH, but there were differences in color between the beer samples.
  • Enhanced Apple Cider Fermentation by Selective Light Exposure
    Wright, Melissa; Williams, Robert; Hurley, E. Kenneth; Eifert, Joseph D.; Lahne, Jacob (2019-04-26)
    Fermentation represents a large segment of post-harvest agricultural processing nationwide. Virginia is a leading state in the production of apples and has shown significant growth in the area of hard cider production. Consumer preference drives the hard cider market and new hard ciders are being introduced frequently. In an effort to enhance the quality of hard cider, this project sought to understand the effect of selected light (color and intensity) exposure during fermentation of apple cider on color and sensory characteristics of the resulting hard cider. Apple juice was inoculated with Saccharomyces cerevisiae and placed into a vertical glass fermentation vessel. Light of selected colors (red, yellow, green, blue, and ultraviolet) and intensities (low, medium and high) was applied to the apple juice during fermentation. Juices were allowed to ferment for 187 ± 3 h, followed by sensory and color analysis. Hard cider exposed to ultraviolet light during fermentation was most different from the dark control (fermented with no light exposure) and most preferred by sensory panelists on the basis of taste. Ultraviolet light-treated ciders were less yellow in color as compared to the dark control. Modifying the color and intensity of light may yield hard ciders with improved sensory characteristics and provide cider makers with processes to enhance quality of traditionally fermented products. This project was funded by a grant from the Virginia Agricultural Council.
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    Photolyase: Its Damaged DNA Substrate and Amino Acid Radical Formation During Photorepair
    Hurley, E. Kenneth (Virginia Tech, 2005-01-06)
    Ultraviolet light damages genomic material by inducing the formation of covalent bonds between adjacent pyrimidines. Cis-syn cyclobutane pyrimidine dimers (CPD)constitute the most abundant primary lesion in DNA. Photolyase, a light-activated enzyme, catalytically repairs these lesions. Although many steps in the photolyase-mediated repair process have been mapped, details of the mechanism remain cryptic. Difference FT-IR spectroscopy was employed to obtain new mechanistic information about photorepair. Purified oligonucleotides, containing a central diuracil, dithymidine, or cyclobutane thymidine dimer, were monitored using vibrational methods. Construction of difference infrared data between undamaged and damaged DNA permitted examination of nucleic acid changes upon formation of the CPD lesion; these experiments indicated that C=O and C-H frequencies can be used as markers for DNA damage. Furthermore, in purified photolyase containing isotopically-labeled aromatic amino acids, we observed that tryptophan residues in photolyase underwent structural changes during photorepair. These data indicate that electron transfer during DNA repair occurs through-bond, and that redox-active, aromatic residues form the pathway for electron transfer.