Contribution of volatility

Model results in seawater are in good agreement with observational data of PFOA. Most differences can be attpageributed to deficiencies of the emission scenario. Despite this fact, the difference between model results and observational data are due to the limited horizontal and process resolution and the fact that the physical parameters of the model (temperature, surface pressure, vorticity or divergence of the wind velocity field) were not relaxed to observational data. Regarding these limitations, in particular individual vertical profiles compare quite well with observations. This study underlines the importance of the ocean as a transport medium of PFOA. The contribution of volatile precursor substances to long-range transport needs to be assessed. 

The solubility of a solute in scC02 is extremely dependent on its structure, with three features of paramount importance. As expected, compounds of low polarity are more soluble than very polar compounds or salts. However, solubility also increases greatly with increasing vapour pressure of a substrate. To account for the contribution of volatility and solvation to the solubility process, Kurt Zosel coined the term Destraktion (from Latin destillare and extrahere) in his pioneering work on natural product extraction with SCFs [5], Finally, some specific functional groups like perfluoroalkyl and polysiloxane substituents, or polyether/polycarbonate copolymers... 

For estimating the contribution of volatile compounds to bread aroma Rothe and coworkers (S) defined "aroma value" as the ratio of the concentration of some volatile compounds to the taste threshold value of the aroma. This concept was further developed by Weurman and coworkers (9) by introducing "odor value", in which aroma solutions were replaced by synthetic mixtures of volatile compounds in water. These mixtures showed the complexity of the volatile fractions of wheat bread, because none of them resembled the aroma of bread. Recently two variations of GC-sniffing were presented (10-11), in which the aroma extract is stepwise diluted with a solvent until no odor is perceived for each volatile compound separately in the GC effluent. The dilution factors obtained indicate the potency of a compound as a contributor to the total aroma. 

Johnson, P.C., Assessment of the contribution of volatilization and biodegradation to in situ air sparging performance, Environ. Sci. Technol, 32(2), 276-281, 1998. 

Tominaga, T., Baltenweck-Guyot, R., Peyrot des Gachons, C., and Dubourdieu, D. (2000). Contribution of volatile thiols to the aromas of white wines made from several Vitis vinifera grape varieties. Am. J. Enol. Vitic. 51,178-181. 

Solvent extraction (diethylether) and vacuum distillation were evaluated as techniques to remove aroma constituents from brewed coffee. Despite multiple extractions or repeated distillations, the aroma constituents of coffee could not be entirely removed. The treated coffee contained a woody, heavy, burned aroma. Results demonstrate that it is difficult to effectively separate the volatile aroma constituents from a food product which obtains its flavor from Maillard reactions and thus the relative flavor contribution of volatile vs non-volatile components is difficult to access. 

Spillman, P. 1., Sefton, M. A., Gawel, R. (2004b). The contribution of volatile compounds derived during oak barrel maturation to the aroma of a Chardonnay and Cabernet Sauvignon wine. Aatst. J. Grape Wine Res., 10, 227-235. 

Bergman, li. M. (1990). Energy contributions of volatile fatty acids from the gastrointestinal tract in various species, Physio . Rtv. 70, 567-590,... 

The contribution of volatility on solubility at constant density and different temperatures for Cu(BDTC)2 is shown in Figure 14. It is obvious that the solubility increases although the solvent properties are the same ( same density at different temperatures). 

The vapor pressure depression method has the advantage of smaller sample size. However, it is not as precise as the freezing point method and cannot measure the contribution of volatile solutes such as ethanol. This method is not used as widely as the freezing point depression method in clinical laboratories. 

The main volatile compounds detected from autoxidized trilinolein monohydroperoxides include pentane, hexanal, 2-heptenal and 2,4-decadienal. The volatiles from trilinolenin and monohydroperoxides include propanal, 2,4-heptadienal and 2,4,7-decatrienal. Mixtures of 1 1 trilinolein and trilinolenin autoxidized at low peroxide values (PV 34) show equal contribution of volatiles derived from linoleate and linolenate hydroperoxides. 

Johnson, P. C. 1998. Assessment of the Contributions of Volatilization and Biodegradation to In-situ Air Sparging Performance, Environmental Science Technology, voL 32, no. 2, pp. 276-281. 

One finds that pH influences both the taste and the aroma of a food. In terms of taste, hydrogen ion concentration is generally linked to the tartness of a food the lower the pH, the more tart the food tastes. While the effect of pH on taste is well recognized, pH also influences the release of some aroma chemicals, i.e., those that act as acids or bases. For example, one would expect the contribution of volatile acids to aroma to be enhanced in aqueous solution at lower pHs, i.e., those below the pKa of the acid. At low pHs, the acid would be in its protonated form (not ionized) and thus be less soluble in the aqueous phase. This would tend to drive the acid into the sample headspace, increasing its contribution to aroma. Basic odorants (e.g., amines or pyrazines) would behave in an opposite manner. These compounds would become more soluble in the aqueous phase below their pKa since they would be ionized and thus more soluble. This would decrease their contribution to aroma at low pHs. The effect of pH on aroma is obvious when one increases the pH of a traditional acidic food or tries to produce a good chocolate flavor in low pH foods (typically neutral or slightly basic). 

R. Buttery, J. Turnbaugh, and L. Ling, Contributions of volatiles to rice aroma, J. Agr. Food Chem. 36 1006-1009 (1988). 

G. Urhach, The flavor of mUk and dairy products 11. Cheese contribution of volatile compounds, Int. J. Dairy Technol. 50 79 (1997). 

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