Volatile in food

The P T technique is frequently used for determination of volatiles in food and beverages [40, 41], plants [42], natural water and wastewater [43, 44], sediments [45], and cow slurries [46]. The technique is widely recommended by the EPA. 

Monitoring the emissions of VOCs has many potential applications in the food industry, since biological materials that are aged, cooked, treated, etc. often release characteristic signature volatiles that can be indicators of the extent of changes in the food product. There has been considerable development of chemical sensors (i.e. electronic noses ) to detect such volatiles. The following examples illustrate how PTR-MS methods can also be used to detect signature volatiles in food research. 

Weurman, C. (1969) Isolation and concentration of volatiles in food odor research... 

The surrounding medium of encapsulated aroma such as polysaccharides, proteins, lipids, and salts could play an important role in release in liquid media and then on aroma compound retention by the film matrix. Different behaviors have been observed in the presence of salt or sucrose molecules of aroma compound volatility in food products, observing that some of them presented a salting out effect (favored release by volatilization), others an opposite salting in effect, and for some others no modification (Lubbers et al., 1998 Van Ruth et al., 2002). Similar effects could be observed in the release of the aroma compounds encapsulated in films. While the salting out effect should accelerate the release, the salting in could decrease the rate of the release. 

To explore the full picture with respect to sustainability, social factors have to be taken into account as well. At present, the effect of the increased use of renewable raw materials on the availability and price of food is a subject of intense debate. It is not yet clear which factors are responsible for the recent volatility in food prices. While the World Bank estimates the influence of biofuels at 75%, the FAO also points to other factors that contribute to the rise in prices. These include changed nutritional habits in many emerging countries, poor harvests and increased fuel prices, which account for about 30% of production costs. 

Sulfur compound investigation can be significantly aided by the use of the SCD. It has been proven to be a sensitive, selective GC detector for sulfur volatiles in food matrixes. In order to achieve accurate results, sample handling and analytical conditions need to be controlled carefully to minimize any reactions involving sulfur flavor volatiles. Thiols and sulfides have been shown to be susceptible to oxidation... 

Table 1. Amount of Volatiles in Food and Number of Aroma Components Therein...

Sorptive extraction (Solid Phase Micro Extraction [SPME] and Stir Bar extraction) are relatively new techniques for the isolation of food aromas. Pawliszyn s group [41] was the first to develop the SPME method, and they applied it in environmental analysis. Since then, it has become a widely used technique for the analysis of volatiles in foods. Harmon [42] and Marsili [43] have provided a comprehensive review and a critical review, respectively, of this technique. 

Esters are quite important to the flavor of both natural foods (e.g., fresh fruit) and fermented foods. Of the fermented foods, esters probably are most important to the flavor of some of the alcoholic beverages. The TNO-CIVO [85] compilation of volatiles in foods lists 94 esters that had been identified in beer. Most of the esters found in beer are formed via primary fermentation. They are produced intracellularly in yeast by enzymatic action [86]. Lipid metabolism by the yeast provides a large number of acids and alcohols that may undergo esterification to yield a variety of esters. While pure chemical reactions can lead to ester formation, this reaction is... 

Carbonyls are quite important to the flavor of cheeses. The TNO-CIVO compilation of volatiles in foods lists 29 carbonyls as having been identified in Cheddar cheese at that time. Carbonyls (methyl ketones) may arise in fermented prodncts iiutiaUy via lipase activity of the starter cnlture. Dairy products contain a significant quantity of a-keto acids which are readily hydrolyzed from the triglyceride by microbial lipases and then decarboxylated to form odd carbon nnmber methyl ketones. 

Central Institute of Nutrition and Food Research (2003) Mass Spectra of Volatiles in Food (SpecData), 2nd edn, John Wiley Sons, Inc., ISBN 978-0-471-64825-3, November 2003. 

Chemical Concepts distributes a collection of its own with 40000 spectra and structures which has undergone a manual quality control check by MS experts. Other special collections contain data on steroids, petrochemicals, and volatiles in food. 

J. R. Vercellotti, O. E. MiUs, K. L. Bett, and D. L. Sullen, Gas chromatographic analyses of lipid oxidation volatiles in foods. Lipid Oxidation in Food (A. J. St. Angelo, ed.), American Chemical Society, Washington, DC, 1992, p. 232. 

Chemical compounds having odor and taste number in the thousands. In 1969 a description of the odor characteristics of more than three thousand chemical compounds used in the flavor and perfume industries were described (41). The Hst of volatile compounds found in food that may contribute to odor and taste is even larger (42), and the Hst of all possible flavor compounds, including those that have yet to be synthesized, is greater than a thousand. Many different compounds have the same flavor character or quaUty, differing perhaps in their relative intensity but indistinguishable in the type of flavor they ehcit. The exact number of different flavor quaUties is not known, but it appears to be much less than the total number of compounds with flavor. 

H. Maarse and C. A. Visscher, eds. Volatile Compounds in Food, Qualitative Data, 5th ed., Zeist, the Netherlands, 1983. 

The efficient recovery of volatile nitrosamines from frankfurters, followed by gc with chemiluminescence detection, has been described (133). Recoveries ranged from 84.3 to 104.8% for samples spiked at the 20 ppb level. Methods for herbicide residues and other contaminants that may also relate to food have been discussed. Inorganic elements in food can be deterrnined by atomic absorption (AA) methods. These methods have been extensively reviewed. Table 8 Hsts methods for the analysis of elements in foods (134). 

H. Marse, C. Visscher, L. WiUemsens, and M. H. Boelens, Volatile Compounds in Food Qualitative and Quantitative Data, Vol. II, TNO-CIVO, Food Analysis Institute, A. J. Zeist, The Nethedands, 1989, pp. 661—679. 

GC using chiral columns coated with derivatized cyclodextrin is the analytical technique most frequently employed for the determination of the enantiomeric ratio of volatile compounds. Food products, as well as flavours and fragrances, are usually very complex matrices, so direct GC analysis of the enantiomeric ratio of certain components is usually difficult. Often, the components of interest are present in trace amounts and problems of peak overlap may occur. The literature reports many examples of the use of multidimensional gas chromatography with a combination of a non-chiral pre-column and a chiral analytical column for this type of analysis. 

Entz RC, Thomas KW, Diachenko GW. 1982. Residues of volatile halocarbons in foods using headspace gas chromatography. J Agric Food Chem 30 846-849. 

N-Nitrosamines, formed principally from the reaction of naturally occurring secondary amines with nitrites that may be added to foods or produced by bacterial reduction of nitrates, have been identified in many food systems including cured meat products, nonfat dried milk, dried malt and beer. In addition, the presence of less volatile and non-volatile N-nitroso compounds or their precursors in foods have been suggested from a number of model system studies. 

Formation of Non-Volatile N-Nitroso Compounds in Food Systems... 

The functions of nitrite and the formation of volatile N-nitrosamines in food systems and their toxicity have been well... 

In the last fifteen years there has been considerable interest in the analysis of volatile N-nitrosamines in foods. The primary focus has been on meat cured with nitrite (3 ) although nitrosamines have been shown to occur occasionally in other foods such as fish and cheese (, 3) Recently, attention has been directed to volatile nitrosamines in beer and other alcoholic beverages. The purpose of this paper is to review current information on the presence of nitrosamines in beer, and to discuss work done in our laboratory and elsewhere on the mode of formation of nitrosamines in beer. 

Major emphasis in studies of N-nitroso compounds in foods has been placed upon volatile nitrosamines, in part because these compounds are relatively easy to isolate from complex matrices by virtue of their volatility. Procedures utilizing atmospheric pressure or vacuum distillation have been used by most investigators, with variations of the method of Fine e al. (2) being among the most popular. This procedure employs vacuum distillation of a mineral oil suspension of the sample with optional addition of water to improve nitrosamine recovery from low moisture content samples (6) The usual approach to prevention of nitrosamine formation during analysis involves adding sulfamic acid or ascorbate to destroy residual nitrite at an early stage of sample preparation. 

Egan, H. Preussmann, R. Walker, E.A. Castegnaro, M. Wasserman, A.E. Eds. "Environmental Carcinogens Selected Methods of Analysis Vol. 1 - Analysis of Volatile Nitrosamines in Food." lARC Scientific Publications No. 18. International Agency for Research on Cancer Lyon, 1978. Walker, E.A. Griciute, L. Castegnaro, M. Borzsonyi, M., Eds. "N-Nitroso Compounds Analysis Formation and Occurrence" lARC Scientific Publications No. 31. International Agency for Research on Cancer Lyon, 1980. Hedler, L. Schurr, C. Marquadt, P. J. Am. Oil Chem. Soc. 1979, 681-684. 

The lipase-catalyzed fatty acid ester hydrolysis and the lipoxygenation of free polyunsaturated fatty acids are involved in the same lipid degradation pathway. They are respectively the first and second reaction in the lipoxygenase pathway (Fig. 3) [87-91]. The pathway produces volatile products of considerable importance in food technology including Cg[92, 93] or Cg- 94—96 aldehydes and alcohols from polyunsaturated fatty... 

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