Promotionsarbeit--Techn. hochschule, Zürich. / Lebenslauf. Includes bibliographical references.

Acidulants can contribute considerably to the flavor of food. However, limited research on differences in acid flavor exists. While numerous researchers have studied acids, most have focused on sourness exclusively. Acids have been shown previously to differ in non-sour components, such as bitterness and astringency. A series of experiments were conducted to determine flavor characteristics of selected acids in different systems. First, selected acids (lactic, malic, citric, acetic) and 2 acid blends (lactic/acetic 1:1 and 2:1) in a model (water) system were evaluated on an equivalent weight (0.2% w/v) and on an equivalent pH basis. Three pH levels were explored: 3.5, 4.5 and 6.5. The technique of free-choice profiling was applied to characterize the flavor profile. Results analyzed by generalized procrustes analysis showed two significant findings: (1) acids differ in sensory character, and (2) the flavor of an acid changes with pH. Second, selected acids (lactic, malic, citric, tartaric) were evaluated in sweetened, flavored drinks on an equivalent weight basis at two concentrations (0.4 and 0.6% w/v). Four flavors were evaluated: orange, cherry, cola and strawberry. Descriptive analysis was used, and the data was analyzed by principal component analysis. Significant differences were found on among acids and concentrations. For the orange flavor system, citric acid enhanced the orange flavor of the drink. Third, selected acids (lactic, citric, acetic) and 2 acid blends (acetic/lactic 1:1 and 2:1) were evaluated in emulsions on an equivalent pH basis. Three pH levels were explored: 3.5, 4.5 and 5.5. These findings support the first study as differences were found among acids, and flavor changes existed when pH changed. / Graduation date: 1995

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic references (p.120-131).

Graduation date: 1962

Thesis (MScAgric)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--Columbia University, 1938. / Vita. Bibliography: p. [23].

Thesis (M.App.Sc.) - University of Queensland, 2005. / Includes bibliography.

Proefschrift--Groningen. / English summary. "Literatuuroverzicht": p. [3]-10.

By virtue of their fragrance and therapeutic nature, essential oils have gained great application in the cosmetic and pharmaceutical industries. These oils, as products consumed by the public for the general health and cosmetics, should be of high quality and unadulterated. In this project comprehensive two-dimensional gas chromatography (GCxGC) was used for the qualitative analysis of some South African essential oils. The main purpose of the project was to evaluate GCxGC for identification of essential oil constituents and for fingerprinting the different essential oils for quality control purposes. Essential oils of the same kind but of different origin were compared and the quantitative variation between their components was studied. Gas chromatography-time-of flight mass spectrometry (GC-TOFMS) as well as comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GCxGC-TOFMS) was used to help identify component peaks separated in the GCxGC instrument. Once certain precautions are taken and the delicate modulator is correctly optimized, the GCxGC results are reproducible and easy to interpret. Overall, the GCxGC technique utilized showed good promise for quality control of essential oils. / Dissertation (MSc)--University of Pretoria, 2006. / Chemistry / unrestricted

Ruminant products, meat and milk, were long ago discovered to contain a high content of saturated fat associated with various chronic diseases in human, including coronary heart disease. Increased consumption of n-3 fatty acids, linolenic (LNA; 18:3n-3), eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) by man has been linked with reduced incidences of these diseases. Therefore, in vitro experiments carried out in this thesis investigated the possibility that the dietary inclusion of essential oil compounds (EOC) might modify ruminal biohydrogenation of polyunsaturated fatty acids (PUFA), and thereby improve the fatty acid profiles of ruminant derived foods. In the first experiment, twenty EOC were screened, of which carvacrol, thymol, cis/trans-citral, geraniol, nerol, (+)-α-pinene, l-menthone, linalyl acetate and (R)-(+)-pulegone were most effective at protecting the PUFA from biohydrogenation. The reduced accumulation of stearic acid with concomitant increases in vaccenic acid following the addition of the EOC confirmed their capacity to inhibit biohydrogenation of both LA and LNA. However, the observed decreases in total volatile fatty acids concentrations suggested that the inclusion of these compounds at 300 mg l-1 also suppressed microbial fermentation. Of these EOC, carvacrol and thymol were the most potent inhibitors of fermentation as they decreased total VFA concentrations by ≥60% from those of the control. In the second experiment, selected EOC, namely linalyl acetate, l-menthone and (+)-α-pinene, were tested at lower doses. It was observed that these EOC when added at 100 and 200 mg l-1 also inhibited biohydrogenation with minimal effect on VFA concentration. In experiment 3, pure culture work was undertaken to assess the effects of EOC on three key Butyrivibrio spp., involved in the biohydrogenation process, namely B. fibrisolvens, B. hungatei and B. proteoclasticus. The EOC inhibited biohydrogenation through their bacteriostatic effects on these bacteria. In conclusion, these studies revealed that EOC have the potential to modify ruminal biohydrogenation to varying extents depending on the type of compound used and the dose applied. Consequently, they might be useful at improving the healthiness of ruminant products, however their effects have to be confirmed in vivo and ensure that they do not cause significant inhibition of fibre digestion.