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Libin Wang, Elizabeth A. Baldwin, Zhifang Yu, and Jinhe Bai

-ionone, hexanal, β-damascenone, 1-penten-3-one, 3-methylbutanal, trans- 2 - hexenal, 2-isobutylthiazole, 1-nitro-2-phenylethane, trans -2-heptenal, 2-phenylacetaldehyde, 6-methyl-5-hepten-2-one, cis -3-hexenol, 2-phenylethanol, 3-methylbutanol, and methyl

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

volatile compounds were detected in northern Xinjiang cultivars. This suggests that Xinjiang apricot cultivars are rich in aroma compounds. Propyl acetate, 3-methyl-1-butyl acetate, ( Z )-3-hexen-1-ol acetate, d -limonene, β-linalool, and hexanal were all

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Durward Smith and Susan Cuppett

Both fresh and frozen asparagus rapidly deteriorate in quality due, in part, to the formation of oxidative off-flavors. Anti-oxidants and chelating agents prevent lipid oxidation in vegetables, but increasing the levels of such compounds in whole vegetables is difficult. Vacuum infusion was optimized to saturate asparagus spears with ascorbic acid without damaging tissues. The combination of vacuum infusion of ascorbic acid and thermal blanching effectively prevented the formation of oxidative off-flavors and hexanal during frozen storage. Sensory evaluations correlated with hexanal levels following frozen storage.

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Jinhe Bai, Elizabeth Baldwin, Jack Hearn, Randy Driggers, and Ed Stover

not shown). Twenty compounds were detected in all samples, including limonene, β-myrcene, α-pinene, α-terpinene, terpinen-4-ol, linalool, ethyl butanote, ethyl pentanoate, ethyl acetate, acetaldehyde, hexanal, nonanal, ethanol, and hexanol (data

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Robert C. Ebel

Apple leaves were shown to increase 6 volatile compounds in response to drought stress severe enough to promote senescence. Apple trees were allowed to dry to -2.0 MPa and -2.7 MPa, levels that were previously shown to reduce fruit growth by 50% and 70%, respectively. The 6 volatile compounds measured included hexanal, (E)-2-hexenal, 1-hexanol, (E)-2-hexen-l-ol, hexyl acetate, and (Z)-3-hexenyl acetate. Hexanal, (E)-2-hexenal, and 1-hexanol have been previously shown to be byproducts of lipoxygenase (LOX) activity. There is considerable information in the literature implicating LOX as a key enzyme involved in senescence, whether induced by pathogenic infection, insect feeding, or in ripening climacteric fruit and vegetables. It is reasonable to propose that LOX is also involved in promotion of senescence induced by drought stress.

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Ravindranath V. Kanamangala, Neils O. Maness, Michael W. Smith, Gerald H. Brusewitz, and Sue Knight

Shelf life is a major problem in the marketing of pecans, particularly at the retail level. A procedure to extend the shelf life of pecans was described. The full-oil and supercritical carbon dioxide extracted (22% and 27% reduced-oil) native pecan kernels packaged in standard air mixture (21% O2, 79% N2), stored for up to 37 weeks at 25 °C and 55% RH, were subjected to hexanal analysis, sensory analysis, and determination of lipid class changes, that occur as the pecans age. Hexanal concentration of reduced-oil pecans was negligible throughout the storage, while full-oil pecans reached excessive levels by 22 weeks. Hexanal analysis was in agreement with the sensory scores. Free fatty acid lipid class was selectively extracted during the partial oil extraction process. Reduction in free fatty acids, and an overall reduction in lipid content on a per kernel basis, decreased the sites for oxidative deterioration and contributed to enhanced shelf-life of pecans. Work was supported by OCAST grant AR4-044 and the Oklahoma Agricultural Experiment Station.

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Ming Zhang and Eric E. Roos

All kinds of plant seeds evolve volatile compounds during storage. However, a reliable deterioration forecast method is still not established using volatile evolution, even though some preliminary work indicated a relationship between volatile evolution and seed deterioration (Fielding and Goldsworthy, 1982; Hailstones and Smith, 1989; Zhang et al., 1993). Here we review some of the previous work concerning seed volatiles and present some more recent research on the effects of seed moisture content on deterioration. We found that volatile evolution from seeds was controlled by seed moisture level. Generally, seeds tended to evolve more hexanal and pentanal under extremely dry conditions (below 25% equilibrium RH). The production of hexanal and pentanal decreased with increasing seed moisture level. On the other hand, methanol and ethanol increased with increasing seed moisture. All of the volatile compounds accumulated in the headspace of the seed storage container during storage. Therefore, it should be possible to use different volatiles to indicate the deterioration of seeds stored under different moisture levels. We suggest that hexanal may be used for seed assessing deterioration under dry storage conditions (below 25% equilibrium RH), while ethanol may be used for seeds stored under higher moisture conditions (above 25% equilibrium RH). [References: Fielding, J.L. and Goldsworthy, A. (1982) Seed Sci. Technol. 10: 277–282. Hailstones, M.D. and Smith, M.T. (1989) Seed Sci. Technol. 17: 649–658. Zhang et al. (1993) Seed Sci. Technol. 21:359–373.]

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E.A. Baldwin

More than 400 volatile components have been identified in tomato fruit, of which only 10–16 are likely to be important contributors to tomato flavor/aroma based on odor threshold data. Tomato volatiles are grouped as lipid-derived, carotenoid-related, amino acid-related, lignin-related, or of uncertain origin. These flavor components are either present in intact fruit or formed after blending due to mixing of previously compartmentalized enzymes and substrates. Lipid-derived volatiles are the biggest group containing cis-3-hexenal and hexanal, which are quantitatively the major volatile compounds in tomato fruit. cis-3-Hexenal and -ionone have the highest odor thresholds among tomato volatile compounds so far identified. Most of these compounds increase during ripening (or the enzymes, substrates and conditions develop that result in increased levels after blending) and appear to be related to ethylene production. Biosynthetic pathways have been established or suggested for most of the important flavor components, of which lipid degradation is the best-understood. Linoleic and linolenic acids are oxidized to hydroperoxides by lipoxygenase, which are then cleaved to volatile C6 aldehydes (hexanal and cis-3-hexenal, respectively). There are two membrane-associated lipoxygenases (tomloxA and B), of which tomloxB appears to be fruit-specific and increases during ripening. Alcohol dehydrogenase (ADH) has been demonstrated to catalyze the interconversion of trans-hexene-2-al and -2-ol and of trans-hexene-2-al, hexanal and hexanol. The enzyme product of the Adh2 gene is induced by 3% O2, and is developmentally expressed in fruit aside from anoxic induction. Naturally occurring mutants and genetically engineered tomatoes with reduced ethylene production, color and/or retarded ripening patterns show changes in volatile concentrations.

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Elizabeth A. Baldwin, Myrna O. Nisperos-Carriedo, and Manuel G. Moshonas

Whole tomato fruit (Lycopersicon esculentum Mill.), cvs. Sunny and Solarset, were analyzed at 5 different ripening stages for ethylene and CO2 production. Homogenates from the same fruit were prepared for determination of color, flavor volatiles, sugars and organic acids. Of the flavor volatiles measured, only eugenol decreased during ripening in both varieties and 1-penten-3-one in `Sunny' tomatoes. Ethanol, and trans-2-trans-4-decadienal levels showed no change or fluctuated as the fruit matured while all other volatiles measured (cis-3-hexenol, 2-methyl-3-butanol, vinyl guiacol, acetaldehyde, cis-3-hexenal, trans-2-hexenal, hexanal, acetone, 6-methyl-5-hepten-2-one, geranylacetone and 2-isobutylthiazole) increased in concentration, peaking in the later stages of maturity. Synthesis of some volatile compounds occurred simultaneously with that of climacteric ethylene and color. `Solarset' fruit exhibited higher levels of sugars and all flavor components except ethanol, vinyl guiacol, hexanal and 2-methyl-3-butanol in the red stage. There were no differences between these varieties for acids

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Eva Almenar, Rafael Auras, Maria Rubino, and Bruce Harte

The United States is the world's largest producer of blueberries and strawberries. Successful marketing for both of them requires fruit of the highest quality and appearance. However, these fruits have a relatively short postharvest life, mostly due to the incidence of molds such as Colletrotrichum acutatum, Alternaria alternata, and Botrytis cinerea. At present, several natural occurring plant volatiles have been shown to be effective against fungal growth, but, even so, those compounds could not be maintained at constant concentration during the whole postharvest period due to their volatility. In this work, two naturally occurring aldehydes (acetaldehyde and hexanal) were tested and compared against the growth of the above mentioned fungi at 23 °C. After that, the most effective antifungal compound for each fungus was encapsulated in ß-cyclodextrins (ß-CD) and tested during storage period. Both aldehydes were effective in reducing and avoiding fungal proliferation depending on concentration. Fungal proliferation depended on daily, and not initial, volatile concentrations. Volatiles encapsulated in ß-CD showed higher antifungal activity compared to that obtained using the pure volatile during storage. Tested volatiles showed both fungicidal and fungistatic capacities after storage of fungal cultures in air. Results suggested ß-CD-acetaldehyde and ß-CD-hexanal complexes can be used as a new technology to release a naturally occurring antifungal compound during storage against several fungal diseases.