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Jian-rong Feng, Wan-peng Xi, Wen-hui Li, Hai-nan Liu, Xiao-fang Liu, and Xiao-yan Lu

main characteristic aroma volatiles were ascertained by using principal component analysis (PCA) of gas chromatography-mass spectroscopy (GC-MS) results: ( A ) PCA scores plot, ( B ) volatile compound loading plot according to the PCA model: KH

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Diana M. Cheng, Gad G. Yousef, and Mary Ann Lila

-evaporated to dryness. Sterol sample processing for gas chromatography–mass spectroscopy analyses. Extracted sterol samples were prepared and analyzed in triplicate by the Metabolomics Center in the Roy J. Carver Biotechnology Center at the University of

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Dong Sik Yang, Svoboda V. Pennisi, Ki-Cheol Son, and Stanley J. Kays

VOCs and analyzed by capillary gas chromatography–mass spectroscopy (GC-MS) (6890N/5973; Agilent, Palo Alto, CA) equipped with a 30 m length (0.25 mm i.d., 0.25 μm film thickness of 5% phenyl methyl siloxane) capillary column (HP-5MS; Agilent). The

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S. Wee and R.M. Beaudry

Autoxidation products alpha-farnesene of have been implicated in superficial scald induction for apple (Malus domestica cv. Cortland Apple) fruit. We suspect the apple cuticle acts as a sink where α-farnesene can accumulate and eventually autoxidize into hydroperoxides, conjugated trienes, 6-methyl-5-hepten-2-one (ketone), and other compounds. These oxidized byproducts may diffuse back into the peel, thereby initiating the scald process. Cortland apples were stored at 0.8°C. Volatile cuticular components were analyzed at 2-week intervals by gas chromatography–mass spectroscopy. Only two scald-related volatiles were found, 6-methyl-5-hepten-2-one and α-farnesene. The identification of these compounds may allow the determination of cuticular involvement in superficial scald, as well as a possible correlation between the volatiles and apple scald development. α-farnesene concentrations initially increased and was followed by a decline, possibly due to its autoxidation.

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Artur Miszczak, Charles F. Forney, and Robert K. Prange

`Kent' strawberries were harvested at red, pink, and white stages of development, and stored at 15C in the light. Fruit were sampled over a 10-day period and evaluated for volatile production and surface color. Volatile production by red and pink fruit peaked after 4 days of storage. Maximum volatile production by red fruit was 8- and 25-fold greater than maximum production by pink and white fruit, respectively. Aroma volatiles were not detected in the headspace over white berries until 4 days following harvest after which volatile production increased through the tenth day of storage. Changes in the surface color of white berries during postharvest ripening coincided with the production of volatiles. In another experiment, red, pink, and white `Kent' strawberries were stored for 3 days at 10 or 20C in the dark or light. Fruit were then evaluated for volatile production, weight loss, anthocyanin content, and surface color changes. White berries produced volatile esters after 3 days of storage at 20C in the light. Both light and temperature influenced the relative production of the volatiles produced by pink fruit. Fresh weight loss, color change, and anthocyanin content were temperature and light dependent.

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O.T. Chortyk, I.E. Yates, and C.C. Reilly

Leaf surface compounds of pecan [Carya illinoensis (Wangenh.) C. Koch] were analyzed with regard to developmental stage and to susceptibility to infection by Cladosporium caryigenum (Ell. et Lang. Gottwald). Immature and mature leaves of two resistant (`Elliott' and `Sumner') and two susceptible (`Wichita' and `Schley') cultivars were extracted with methylene chloride. Extracts were separated by silicic acid chromatography into polar and nonpolar fractions. Constituents of each fraction were subsequently separated by gas chromatography and were identified by gas chromatography-mass spectroscopy. Leaf surface constituents characterized included long-chain aliphatic hydrocarbons, aliphatic wax esters, triterpenoid constituents, aliphatic alcohols, fatty acids, and diacyl glycerides. The predominant surface compounds on immature leaves were lipids such as fatty acids, fatty alcohols, and glycerides. On mature leaves, lipids declined and aliphatic hydrocarbons and triterpenoids became predominant leaf surface constituents. The changes were observed for all cultivars, regardless of genotypic response to C. caryigenum. Thus, we conclude that cuticular chemicals change dramatically during leaf maturation but do not correlate with resistance to scab disease common to certain pecan cultivars.

Open access

Seon-Ok Kim, Su Young Son, Min Ji Kim, Choong Hwan Lee, and Sin-Ae Park

Mycobacterium vaccae is a species of nonpathogenic bacterium that lives naturally in soil. This study compared the physiological effects at a metabolomic level with autonomic nervous system responses in adults during soil-mixing activities, based on the presence or absence of M. vaccae in the soil. Twenty-nine adult participants performed soil-mixing activities for 5 minutes using sterilized soil with culture media and M. vaccae, respectively. Blood samples were drawn twice from each participant after each activity. Electroencephalograms and electrocardiograms were measured during the activity. Serum metabolites underwent metabolite profiling by gas chromatography, followed by multivariate analyses. Soil-emitted volatile organic compounds were identified using the solid-phase microextraction and gas chromatography-mass spectroscopy, followed by multivariate analyses. The volatile compound analysis revealed that the metabolites related to esters and sulfur-containing compounds are greater in soil with M. vaccae. Serum metabolomics revealed that the treatment group (soil inoculated by M. vaccae) possesses relatively higher levels of inter-alia organic and amino acids compared with the control group (soil mixed with culture media). In the treatment group, the electroencephalogram and electrocardiogram revealed that alpha band activity of the occipital lobe increases, while heart rate decreases. This study concludes that M. vaccae soil contact can affect human metabolic and autonomic reactions.

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Robert D. Belding, Sylvia M. Blankenship, Eric Young, and Ross B. Leidy

Variation in amount and composition of epicuticular wax among several apple (Malus ×domestica Borkh.) cultivars was characterized by gas chromatography, thin-layer chromatography, and gas chromatography-mass spectroscopy. Across cultivars, wax mass ranged from 366 to 1038 μg·cm-2. Wax mass decreased during the 30 days before harvest. Ursolic acid accounted for 32% to 70% of the hydrocarbons that make up the epicuticular wax. Alkanes, predominantly 29-carbon nonacosane, comprised 16.6% to 49%. Primary alcohols of the hydrocarbons ranged from 0% to 14.6% of the epicuticular wax. Secondary alcohols of the hydrocarbons were the most cultivar specific, making up 20.4% of the epicuticular wax in `Delicious' and only 1.9% `Golden Delicious' strains. Aldehydes and ketones of the hydrocarbons represented a small amount of total wax, ranging from 0% and 6.0%. Percentage of primary alcohol in the epicuticular wax increased as fruit developed. Other components showed no distinct trends with fruit development. Examination of the ultrastructure of cuticular wax using scanning electron microscopy revealed structural differences among cultivars.

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Eduardo D. Munaiz, Russell L. Groves, and Michael J. Havey

Onion thrips (Thrips tabaci) is the main insect pest of onion (Allium cepa), and feeding damage routinely causes serious yield losses. Lower amounts of epicuticular waxes on onion leaves have been associated with fewer onion thrips and less feeding damage, and research is needed to assess the relationships between amounts and composition of epicuticular waxes and feeding damage by onion thrips. This study used gas chromatography mass spectroscopy to determine amounts and types of epicuticular waxes on the foliage of onion accessions that had been field-selected for lower damage from onion thrips. Hentriacontanone-16 (H16), octaconasol-1, and triacontanol-1 were the most prevalent waxes on the foliage of these selections. Amounts of H16 were significantly lower on selections visually classified as having glossy or semiglossy foliage. Semiglossy selections were identified with similar amounts of total epicuticular wax as waxy phenotypes, due primarily to lower amounts of H16 and higher amounts of other waxes. These semiglossy selections suffered significantly less feeding damage from onion thrips in a field evaluation, supporting the identification of unique wax profiles toward the development of thrips-resistant onion.

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S. Wee and R.M. Beaudry

Volatile compounds produced by apple (Malus domestica Borkh) fruit partition into the cuticle and epicuticular waxes and may play an important role in superficial apple scald. Of these volatiles, α-farnesene, conjugated trienes, hydroperoxides, and 6-methyl-5-hepten-2-one have been identified as playing a crucial role in scald production. Volatiles from the epicuticular wax of four different apple cultivars have been analyzed by gas chromatography/mass spectroscopy. A correlation was found between scald incidence and 6-methyl-5-hepten-2-one content and the 6-methyl-5-hepten-2-one:α-farnesene ratio. α-Farnesene is the most-abundant volatile at the beginning of storage, whereas 6-methyl-5-hepten-2-one is present in minute quantities. These two volatile compounds appear to have an inverse relationship with respect to one another since the levels of 6-methyl-5-hepten-2-one increased and α-farnesene decreased prior to the onset of apple scald. This changing ratio may have been due to an autoxidative process resulting in the breakdown of α-farnesene to 6-methyl-5-hepten-2-one. Analysis of the volatiles emanating from the apple wax revealed a number of compounds associated with aroma that also partition readily into the fruit surface.