Flavour mass spectrometry

The oceurrence of a large number of pyrazines as flavouring or aroma eonstituents and as pheromones in extremely low coneentrations has led to mass spectrometry being the method of ehoiee for determining the gross struetural details of a pyrazine nueleus. The method appears to be generally applieable and relatively specifie and sensitive. 

Volatile compounds isolated from strawberry guava fruit by simultaneous steam distillation-solvent extraction were identified by capillary gas chromatography-mass spectrometry (GC-MS) and were characterised sensorially by sniffing GC [52]. Terpenes and terpenic derivatives were identified and were shown to contribute much to the typical strawberry guava flavour. The presence of many aliphatic esters and terpenic compounds is thought to contribute to the unique flavour of the strawberry guava fruit. 

Mosandl, A. (1995) Enantioselective capillary gas chromatography and stable isotope ratio mass spectrometry in the authenticity control of flavours and essential oils. Food Rev. Int. 11 597-664. 

N. (2004) Maturity discrimination of snake frmt (Salacca edulis Reinw.) cv. Pondoh based on volatiles analysis using an electronic nose device eqmpped with a sensor array and fingerprint mass spectrometry. Flavour Fragrance J. 19 44-50. 

Taylor, A.J., Linforth, R.S.T., Harvey, B.A., Blake, B. (2000) Atmospheric pressure chemical ionisation mass spectrometry for in vivo analysis of volatile flavour release. Food Chem. 71 327-338. 

Yerelzian, C., Jordan, A., Brevard, H., Lindinger, W. (2000) Identffication of volatile compunds iKing combined gas chromotography electron impact atmospheric pressure ionization mass spectrometry. In Taylor, A.J., Roberts, D.D. (eds) Flavour Release, ACS Symposium Series 763. American Chemical Society, Washington, pp 58-72. 

Asche S, Beck T, Hener U, Mosandl A (2000) Multidimensional gas chromatography, online coupled with isotope ratio mass spectrometry (MDGC-IRMS) a new technique for analytical authentication of genuine flavour components. In Frontiers of Flavour Science. DFA, Garching... 

Diaz-Maroto, M. C., Guchu, E., Castro-Vazquez, L., de Torres, C., Perez-Coello, M. S. (2008). Aroma active compounds of American oak Quercus alba) and Prench, Hungarian and Russian oak woods Quercus petraea) studied by Gas Chromatography-Mass Spectrometry and Gas Chromatography-Olfactometry. Flavour Fragr. J., 23, DOI 10.1002/ffj.l858. 

Spanel, P., Smith, D. Selected ion flow tube mass spectrometry detection ad real-time monitoring of flavours released by food products. Rapid Commun. Mass Spectrom. 13, 585-597 (1999)... 

Ochiai, N., Sasamoto, K., Daishima, S., Heiden, A.C. and Hoffmann, A. (2003) Determination of stale-flavour carbonyl compounds in beer by stir bar sorptive extraction with in-situ derivatization and thermal desorption-gas chromatography-mass spectrometry, J. Chromatogr. A., 986(1), 101-110. 

The first raw materials for the flavour industry included extracts, tinctures, oleoresins, juice concentrates, essential oils, and a few synthetic chemicals (Tab. 3.1). Up to the 1950s, flavour research was concentrated on the isolation, stmcmral analysis, and synthesis of just a few quantitatively outstanding natural materials (Tab. 3.1). The situation changed dramatically with the advent of gas chromatography as a means of analysis, especially in conjunction with mass spectrometry. 

Model reaction trials and modem analytical methods (gas chromatography/mass spectrometry (GC/MS), gas chromatography/olfactometry (GC/0)) permitted the identification of key mechanisms responsible for flavour generation in process flavourings and some of the most important ones are detailed below. Often chemically complex precursor raw materials (vegetables such as onions, spices, yeast extracts, animal products) are used. Research work on these complex reactions is rare but necessary and allows the discovery of new key odorants and formation pathways. For example, Widder and co-workers [13] discovered a new powerful aroma compound, 3-mer-capto-2-methylpentan-l-ol in a complex process flavour based on onion. 

These interface techniques for connecting the HPLC with the MS-system are very sensitive for most of the substances of interest to the flavour industry. Therefore, HPLC-MS coupling techniques have become an increasingly powerful tool for quality control of flavourings, especially for the analysis of complex mixtures like process flavourings or contaminants present in such complex mixtures. New developments in the area of mass detection systems, such as time-of-flight (ToF) mass analysers and tandem mass spectrometry systems or the features of matrix-assisted laser desorption ionization (MALDI) techniques, may enhance the analytical capabilities of these systems in the near future [16, 17, 28-31 ]. 

The isotopic characterisation of organic compounds by classical elemental analysis with isotope ratio mass spectrometry (EA-IRMS) demands milligram amounts of pure compounds, which can not always easily be provided. Most analytes in flavour characterisation are volatile, and therefore, after their extraction, coupling of (capillary) gas chromatography (cGC) with IRMS would be an ideal tool for the isotope ratio analysis of the individual substances. For C- ]127, 128] and N-analysis ]179, 180] this has been realised for a long time by combining GC to IRMS via a combustion (C) unit (GC-C-IRMS), even for polar substances after their derivatisation ]181, 182]. 

Demyttenaere, J.C.R., Dagher, C., Sandra, P., Kallithraka, S., Verhe, R., and De Kimpe, N. (2003). Flavour analysis of Greek white wine by solid-phase microextraction-capillary gas chromatography-mass spectrometry J. Chromatogr. A, 985,233-246. 

The coupling of SNIF-NMR with stable isotope ratio analysis/mass spectrometry has been the basis of a method for detection of adulteration of maple syrup with beet, cane, or com sugar.192 Adulteration of mustard oil by the addition of synthetic allyl isothiocyanate, its major component, is of economic interest, and therefore a combined NMR and mass spectrometry method was developed, enabling the distinction between the natural and the synthetic compound, as well as the determination of the geographical origin of natural mustard oils.193 Similar methods have been used for the analysis of flavourings such as vanilla flavour (vanillin and p-hydroxybenzaldehyde),194195 benzaldehyde,196 and others.197... 

Merritt C. Jr. and Robertson D.H. (1982) Techniques of analysis of flavours. Gas chromatography and mass spectrometry. In Food Flavours. Part A. Introduction. Morton I.D. and McLeod A.J. Eds, Elsevier Scientific Publishers, Amsterdam 3A, 49-78. 

Thomas A.F., Willhalm B. and Flament I. (1984) Some aspects of GC-MS in the analysis of volatile flavours. Chromatography and Mass Spectrometry Nutr.Sc.Food Safety, Frigerio and Milton Eds, Elsevier, Amsterdam, pp. 47-65. 

In GC, the mobile phase or carrier phase is an inert gas such as helium and the stationary phase is a very thin layer of liquid or polymer on an inert solid support inside a column. The volatile analytes interact with the walls of the column, and are eluted based on the temperature of the column at specific retention times (Grob Barry, 2004). The eluted compoimds are identified with detectors. Flame ionization and mass spectrometry are the most commonly used detectors for flavour analysis (Vas Vekey, 2004). 

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