The effect of refluxing on the aromas of Valencia aqueous orange essences was determined through analysis by GC, MS, Osme, and by a descriptive panel. The strengths and descriptions of volatiles were investigated to determine if differences in essence aroma character and intensity existed. During production, 1 sample was subjected to reflux conditions and contained 16.2% ethanol. The other sample had not been refluxed and contained 6% ethanol. The aroma activity of volatiles was measured by Osme, a method of gas chromatography / olfactometry developed at Oregon State University. The majority of aroma active peaks were found to be present in the reflux and no reflux aqueous orange essence samples. Octanal, linalool, ethyl butanoate and 2 unknowns were the components with strongest aroma activities in both samples. Descriptive analysis was conducted with 7 trained panelists from the Food Science and Technology Department at Oregon State University. Following 12 training sessions, initial testing indicated overall intensity was the major separating attribute of essences. After 6 additional training sessions and adjustment of concentrations to yield essences of approximate equal strength, testing indicated there were no significant differences between samples. Osmegrams, GC FID chromatograms, and descriptive analysis indicated the effect of reflux produced an essence that was more concentrated. Although refluxing concentrated individual volatiles to different levels, character differences other than those associated with concentration were minimal. / Graduation date: 1996

A study of some aspects of essential oil secretion in plants was conducted. The first part of the study involved analysis of the volatile terpenoid content and composition of leaf extracts from a range of Australian native plants by gas chromatography and mass spectrometry. Secretory structures were studied by several microscopic imaging techniques including conventional bright and dark field optical microscopy, confocal microscopy, and scanning (SEM) and transmission (TEM) electron microscopy. Three methods were employed for scanning electron microscopy. Sample material was prepared for conventional SEM by chemical fixation and rapid freeze fixation, and fresh material was imaged by environmental SEM. These methods were compared, and the images acquired by environmental SEM were invariably of a superior standard as the biological integrity of the samples was retained throughout, and the samples were free of process-induced artefacts. Several other tests were conducted and results discussed in some detail. In the final part of the study, aspects of essential oil secretion were examined by histochemical methods. The first of these was a new method based on traditional approaches to histochemistry. The monoterpene phenols thymol and carvacrol were located in glandular trichomes of Lamiaceae species by means of a colour-change reaction of the phenols with a nitrosophenol/acid reagent. The second used magnetic resonance imaging by a chemical shift selective method to locate, non invasively, the aromatic monoterpenes thymol and anethole in secretory structures in the fruit of Carum copticum (Apiaceae) and the leaves of Backhousia anisata (Myrtaceae) respectively. / Doctor of Philosophy (PhD) (Science)

Thesis (M. Sc.)(Chemistry)--University of Pretoria, 2006. / Summaries in English and Afrikaans. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (Ph. D.(Chemical Engineering)--University of Pretoria, 2000. / Summaries in English and Afrikaans. Adobe Acrobat Reader needed to open files.

No description available.

Thesis (Ph. D.)--University of Western Sydney, 2003. / A thesis presented in fulfilment of the requirements for the degree of Doctor of Philosophy, College of Science, Technology and Environment, University of Western Sydney, May, 2003. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 42-46). Also available on the World Wide Web.

Mémoire (M.Sc.)--Université du Québec à Chicoutimi, 1990. / Document électronique également accessible en format PDF. CaQCU

Thesis (PH. D.)--Columbia University, 1932. / Vita. eContent provider-neutral record in process. Description based on print version record. "Literature cited": p. 36-37.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 126-137). Also available on the Internet.