This thesis describes a series of experiments concerned with the production of aromatised rice. The end product showed no visible difference from untreated rice, and the cooked product had a perceivable aroma. The aromatisation process used liquid carbon dioxide as a vehicle to deliver the aroma, and eugenol, isoeugenol, methyl eugenol, cinnamyl alcohol and cinnamaldehyde were used as the principle model aroma components. The aromas penetrated the cores of the rice grains, providing a longer period for the aroma compounds to migrate toward the surface and be lost to the open air. The stability of the injected compounds in aromatised rice was investigated, showing that aroma loss was a first-order process, although some model compounds showed evidence of two binding models, with two distinct phases of aroma loss. The strength of aroma binding to rice was further assessed by means of gas-chromatography columns, and the model aroma compounds interacted best with the rice-flour column. Shelf-life studies demonstrated that eugenol and cinnamaldehyde in aromatised rice showed no significant changes after being stored for 6 months in sealed vacuum aroma-barrier plastic bags, and the aromas could be detected by the human olfactory system after the rice had been cooked by boiling and steaming / Doctor of Philosophy (PhD)

Copies of author's previously published articles inserted. Bibliography: leaves 121-144. This study investigates the site of biosynthesis of flavour compounds in the grapevine. Most of the secondary metabolites, including flavour compounds, are glycosylated and stored in plant tissues as glycosides. The chemical properties of these compounds, especially their water solubility, suggests that glycosides might be forms of translocated secondary metabolites in plants.

This work set out to examine the methodologies of dry hopping, compare different hop materials, and look at the extraction behavior of different types of hop compounds. This work consists of two discrete studies, where the first study informed the design of the second. The first study measured the concentrations of hop aroma compounds extracted from Cascade hops during dry hopping using a model beer system devoid of malt, yeast aromas, and hops. Cascade hops pelletized by four different processors yielded different particle size distributions and pellet densities. These pellets were dosed into a degassed medium (water, 6% v/v ethanol, pH 4.2) and the hop aroma extraction was measured periodically over a one week period. Solid phase micro-extraction (SPME) followed by gas chromatography (GC-FID) was used to analyze the levels of aroma compounds in the extraction medium. Variation in the hop pellet physical properties did not significantly impact the extraction rate of hop volatiles such as linalool, geraniol, limonene and myrcene with one exception. One treatment showed an increased absolute concentration of geraniol. Separately, dry hop aroma extraction was measured over a short time (1 day) at room temperature in an unhopped beer using small-scale (1L), stirred vessels. Irrespective of the hop form (whole or pellet), the concentrations of hydrocarbon terpenes peaked between 3 and 6 hours and subsequently declined, while the concentrations of terpene alcohols continued to increase throughout the 24 hour dry hop extraction. The rate of hop aroma extraction did not appear to be significantly influenced by hop pellet properties and occurred rather rapidly regardless of the hop form. The second study examined the extraction of hop aroma compounds during a pilot brewery scale (~4hL) dry hop treatment. Dry hop treatments consisted of whole cone hops and pellet hops (Cascade cultivar, 2011 harvest) which were dosed into cylindroconical vessels which were either stirred with a pump or left quiescent. Samples were taken for GC-FID and HPLC analysis as well as sensory evaluation at various time points between 30 minutes and 12 days. Polyphenol and alpha acid extraction was highest in a stirred system dosed with pellets. Hop aroma compound extraction was also the highest in the stirred system utilizing pellet hops. The sensory panel rated the stirred pellet samples as having the highest hop aroma, bitterness, and astringency. The results showed that hop flavor from dry hopping can be readily achieved with much shorter contact time than the current 4-12 day industry practice. / Graduation date: 2013

Graduation date: 1995

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisors: Steven K. Dentel and Pei C. Chiu, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis--University of Florida, 1971. / Description based on print version record. Manuscript copy. Vita. Bibliography: leaves 173-190.

No description available.

'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