Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 235-242). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 235-242). Also available on the Internet.

The Sudbury Neutrino Observatory has previously shown that ⁸B solar neutrinos undergo flavor transformation between the Sun and the Earth. This work presents a joint analysis of one-third of the pure D₂O and salt phase data sets with an electron energy threshold of 3.5 MeV. A measurement of the neutral current interaction rate, sensitive to all neutrino flavors, gives a total ⁸B flux of 4.79 ± 0.22 (stat) ± 0.13(syst) × 10⁶ cm⁻²s⁻¹. This is in agreement with the prediction of the Standard Solar Model. For the first time we obtain the v[sunscript e] survival probability separately for downward-going (day) and upward-going (night) solar neutrinos. No significant distortion is observed day or night for ⁸B neutrinos with energies greater than 6 MeV. The lack of distortion, but overall suppression of electron neutrinos relative to the total flux, is consistent with matter-induced neutrino transformation in the Sun and the large mixing angle solution. / text

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Proximate analysis of the commercial shrimp meat waste samples indicated the presence of 94.6% protein and 4.2% fat on a dry basis. The HPLC analysis revealed the presence of 17 amino acids (proline most abundant) and 7 sugars (ribose being the most abundant). The changes in the concentration of the amino acids and sugars after heat treatment, are explained based on their interaction through the Maillard reaction and by the thermal hydrolysis of proteins and polysaccharides present in tissue. Carotenoid pigments ($ beta$-carotene, canthaxanthin, astacene, and astaxanthin monopalmitate) were extracted and separated by thick layer chromatography. Their structures were identified tentatively by thick layer chromatography (TLC) and subsequently confirmed by Fourier transformed infrared (FT-IR) spectroscopy. Lipids were separated and categorized into glycerides, sterols, and phospholipids by thin layer chromatography while flavor-active components were extracted by different organic solvents into acidic, basic, and neutral fractions and their sensory properties determined. The flavor profile of the raw and cooked shrimp meat waste revealed the presence of 59 compounds in raw shrimp compared to 44 in cooked. The components identified were of different functional groups, including fatty acid esters, long chain alcohols, aldehydes, ketanes and hydrocarbons. Many fractions provided desirable aroma (nutty, fruity, floral, green woody, meaty) indicating the presence of important flavor compounds in the commercial shrimp waste. / Model studies were carried out under different experimental conditions (water content, pH), to observe the influence of these parameters on the formation of Maillard reaction products. Furthermore, a comparative study between direct injection of the aqueous solutions and its organic extracts was conducted. The direct injection of aqueous solutions revealed the presence of many water soluble components that were not detected by organic solvent extraction such as droserone and 3,9-diazatricyclo$ lbrack7.3.0.0 sp{*}.3 sp{*}.7 sp{ *} rbrack$-dodecan-2,8-dione while maltoxazine and acetanilide are example of compounds identified only in the dichloromethane extracts. Results also demonstrated that monosaccharides affected the yield of the compounds produced whereas the amino acids influenced the sensory properties of these models. Fructose and ribose were found to be the most reactive sugars in their respective categories. Thiazoles were found to be more water soluble whereas $ beta$-carbolines were more abundant in the organic extracts. The influence of water content was investigated in model systems containing fructose or glucose. It was found that water free systems decreased the yield of pyrazines and thiazoles while the formation of pyrrole and pyridine derivatives increased under dry heating conditions. The formation of Maillard reaction products were studied under different pH conditions in order to assess the effect of pH on the formation of heterocyclic compounds. Pyrazine and furan derivatives were the most affected by pH and alanine was found to be a better nitrogen source than lysine in the formation of pyrazines under different pH conditions. Finally, based on energy minimization studies using MM2 force field, a plausible mechanism was proposed for the formation of maltol in Maillard model systems.

The presence of off-flavor compounds in fish represents one of the significant economic problems encountered in aquaculture. These off-flavor compounds are due to the absorption of substances produced by microorganisms. Currently, a number of strategies have been employed to prevent or limit the growth of these microorganisms in recirculating aquaculture system. Therefore, it is important to evaluate the effectiveness of these strategies by monitoring the concentrations of off-flavor compounds in fish. In-vivo solid phase microextraction (SPME), a rapid and simple sample preparation method, allows the monitoring of concentrations of off-flavor compounds in live fish. In this research, geosmin and 2-methylisoborneol (2-MIB), which are produced by cyanobacteria and actinomycetes being the major sources for “earthy” and “muddy” flavors in fish, were selected as representatives. In order to accurately quantify these compounds in fish muscle, two kinetic calibration methods, on-fibre standardization and measurement using pre-determined extraction rate, were used. Results obtained were validated by traditional methods. The detection limit of in-vivo SPME in fish muscle was 0.12 ng/g for geosmin and 0.21 ng/g for 2-MIB, both below the human sensory threshold. Additionally, the binding effect of geosmin and 2-MIB in fish muscle was investigated in details. Facilitated by the agarose gel model, it was proven that binding did not impact the extraction rate under the pre-determined sampling time. Furthermore, an optional sampling position was undertaken by inserting the fibre into the fat tissue found under the fish belly, the results indicating that this method could decrease extraction time by up to two-thirds of its usual time.

'Marion' and 'Thornless Evergreen' blackberry volatiles were analyzed by capillary gas chromatography-flame ionization detection (GC-FED) and GC-mass spectrometry (GC-MS). Based on total percentage of FID area 'Thornless Evergreen' contains significantly more alcohols, hydrocarbons, and phenols than the 'Marion'; 'Marion' contains more acids and esters. Both cultivars contained comparable amounts of aldehydes and ketones; alcohols were most abundant. The six most abundant volatiles in 'Marion' were ethanol, acetic acid, hexanoic acid, ethyl acetate, linalool, and 2-heptanol; they totaled 52% of total peak area. In 'Thornless Evergreen' the six most abundant volatiles were 2-heptanol, ethanol, 2,3-butanediol, hexanol, α-pinene, and ethyl acetate; they totaled 43% of total peak area. 'Marion' and 'Thornless Evergreen' blackberry aromas were compared using a pair of extraction and gas chromatography-olfactometry-mass spectrometry (GC-O-MS) methods. One method is based on purge-and-trap (P&T, dynamic headspace) extraction and aroma intensity rating by detection frequency (DetF) and a numeric scale, and the other based on solvent assisted flavor extraction (SAFE) and aroma threshold dilution analysis (AEDA). The parallel use of P&T-DetF GC-0 and SAFE-AEDA provided more representative blackberry volatile compositional data than either alone. Eighty-four compounds were identified; seventy-seven were in 'Marion', and sixty-eight in 'Thornless Evergreen'. Thirty-seven have not been previously reported in blackberry. Fourteen volatiles out of eighty-four were described with aroma descriptors specific to bramble fruit (berry, blackberry, bramble, raspberry); no single compound was unanimously described as "characteristically blackberry". Fresh 'Marion' blackberry aroma has been described as floral, fruity, sweet, caramel-fruity, and woody, while fresh 'Thornless Evergreen' aroma is spicy, green, herbaceous, fruity, and sweet. Except for esters, the cultivars contain comparable numbers of acids, alcohols, aldehydes, furanones, hydrocarbons, ketones, phenolics, sulfur, and Theaspirane compounds. Research data implies some portion of the more floral, fruity, and sweet aroma of the 'Marion' blackberry may be the result of additional esters not shared with the 'Thornless Evergreen' blackberry, yet both cultivars apparently contain five furanones, which are powerful sources of sweet, fruity, and spicy aromas. Aroma reconstitution studies will be the key to resolving the significant aroma profile differences between 'Marion' and 'Thornless Evergreen' blackberries, as characteristic blackberry aroma is apparently a complex formulation of volatiles. / Graduation date: 2004

A method for the assessment of volatile compounds in dairy products was developed using solvent desorption dynamic headspace sampling. The method was first applied to assay for diacetyl and acetoin in buttermilk. Major buttermilk volatiles recovered included diacetyl, acetic acid, and acetoin. Normalized detector responses were linear over the range of concentrations tested for diacetyl and acetoin. The method enabled quantitative estimation of diacetyl and acetoin in <30 min, including sample preparation time. Next, the ability of stabilizing and emulsifying agents to inhibit the release of diacetyl from a model dairy matrix was examined using modified purge parameters. Stabilizers (guar, xanthan, and carrageenan) and emulsifiers (lecithin, carboxymethyl cellulose, and Tween 80) were examined for their effects on headspace available diacetyl at 0.05, 0.10, and 0.20% (wt/wt) in a 5% milkfat model system. Guar gum and carrageenan exhibited similar diacetyl release inhibition when corrected for viscosity. Xanthan gum exhibited the greatest decrease in headspace available diacetyl after correction for viscosity at increasing gum levels. Tween 80 imparted no significant viscosity and had no effect on recoverable diacetyl. Lecithin had no effect on viscosity, however it did inhibit the release of diacetyl as a function of lecithin level. Carboxymethyl cellulose increased viscosity and inhibited diacetyl release. Finally, a rapid dynamic headspace sampling technique was evaluated for its ability to differentiate between Cheddar cheese samples for volatile aroma compounds. Seven samples of Cheddar cheese were examined ranging in flavor from mild to extra sharp. A total of 14 volatile compounds were tentatively identified with published retention indices and retention times of known standards. Major volatiles recovered were 2-butanol, acetoin, propanoic acid, butyric acid, and caproic acid. Other identified compounds were 2-butanone, diacetyl, ethyl butyrate, 1-butanol, ethyl caproate, hexanol, acetic acid, 2,3-butanediol, and octanoic acid. The application of solvent desorption dynamic headspace sampling of dairy volatiles is a simple, rapid method for the determination of volatile compounds previously shown to influence flavor and aroma of dairy products. This research was conducted to demonstrate the optimized application of this technology to tracking dairy products aroma compounds. / Graduation date: 1996

Graduation date: 2000

Graduation date: 1994