Flavour / flavouring compounds analysis

A large amount of fuel and environmentally based analysis is focused on the determination of aliphatic and aromatic content. These types of species are often notoriously difficult to deconvolute by mass spectrometric means, and resolution at the isomeric level is almost only possible by using chromatographic methods. Similarly, the areas of organohalogen and flavours/fragrance analysis are dominated by a need to often quantify chiral compounds, which in the same way as aliphatic... 

V. Karl, J. Gutser, A. Dietrich, B. Maas and A. Mosandl, Stereoisomeric flavour compounds. EXVIII. 2-, 3- and 4-alkyl-branched acids. Part 2 chirospeciflc analysis and sensoT y evaluation , Chirality 6 427 - 434 (1994). 

H.-G. Schmarx, A. Mosandl and K. Grob, Stereoisomeric flavour compounds. XXXVIII dkect chir ospecific analysis of y-lactones using on-line coupled EC-GC with a chkal separation column , Chromatographia 29 125-130 (1990). 

The application of ever improving analytical methods will continue to reveal new flavouring compounds, be they natural, nature identical or synthetic. Not only are ever more sophisticated analytical techniques available but also improved methods of data analysis. The new science of chemometrics has developed to cope with the situation where chromatograms with hundreds of compounds are obtained. 

Adahchour, M., van Stee, L.L.R, Beens, J., Vreuls, Batenburg, M.A., Brinkman, U.A.T. (2003) Comprehensive two-dimensional gas chromatography with time-of-flight mass spec-trometric detection for the trace analysis of flavour compounds in food. J. Chromatogr. A 1019 157-172. 

Mariaca, R. Bosset, J.O. (1997) Instrumental analysis of volatile (flavour) compounds in milk and dairy products. Lait 77 13-40. 

It is well-known that in plant tissues certain amounts of flavour compounds are bound as non-volatile sugar conjugates. Most of these glycosides are jS-glu-cosides, but there are other glycones like pentoses, hexoses, disaccharides and trisaccharides too [46]. Acylated glycosides and phosphate esters have also been reported [47, 48]. Information about the analysis of glycosides can be found in the work of Herderich et al. [49]. 

Rychlik, M Warmke, R., and Grosch, W. 1997. Ripening of Emmental cheese wrapped in foil with and without addition of Lactobacillus casei subsp. casei. III. Analysis of character impact flavour compounds. Lebensm.-Wiss. Technol. 30 471-478. 

Flavour and off-flavour compounds of black and white pepper (P. nigrum L.) were evaluated by Jagella and Grosch (1999a,b). Enantioselective analysis of optically active monoterpenes indicated ( )-linalool, (+)-a-phellandrene, (-)-limonene, myrcene, (-)-a-pinene, 3-methylbutanal and meth-ylpropanal as the most potent odorants of black pepper. Additionally, 2-isopropyl-3-methoxypyrazine and 2,3-diethyl-5-meth-ylpyrazine were detected as important odorants of the black pepper sample from Malaysia, which had a mouldy, musty off-flavour. Omission tests indicated a-and (3-pinene, myrcene, a-phellandrene, limonene, linalool, methylpropanal, 2- and 3-methylbutanal, butyric acid and 3-meth-ylbutyric acid as key odorants. A storage experiment revealed that for ground black pepper, losses of a-pinene, limonene and 3-methylbutanal were mainly responsible for deficits in the pepper-like, citrus-like, terpene-like and malty notes after 30 days at room temperature. The musty/mouldy off-flavour of a sample of black pepper was caused by a mixture consisting of 2,3-diethyl-5-methylpyrazine (2.9pg/kg) and 2-isopropyl-3-methoxypyrazine (0.2 (xg/kg). 

Behera et al. (2004) concluded that the optimum conditions for the conventional roasting method were 125°C for 10 min and, in the microwave processing method, the best conditions were 730 W for 10min. The yields and physico-chemical properties of the volatile oils were similar in both cases. Changes were observed in the optical rotation values, which indicated differences in the chemical compositions. GC and GC-MS analysis of optimized condition samples showed that microwave-heated samples could better retain the characteristic flavour compounds of cumin (i.e. total aldehydes) than conventionally roasted samples (Table 11.5). Earlier GC reports showed cuminaldehyde as the only major aldehyde present in Indian cumin oil, but this study revealed the... 

SPME can also be used to extract target analytes from food and drug samples. Thus, it has been employed for the extraction of caffeine from coffee and tea [225], and for that of volatile impurities in drugs. Headspace SPME has also been tested for flavour analysis in foods. Thus, the SPME/GC/TOF-MS tandem was successfully used for the rapid analysis of volatile flavour compounds in apple fruit. The sample (300-450 g of apple) was subjected to static headspace sampling for 4 6 h in order to allow the volatiles... 

The sample material is diluted with demineralized water and extracted with organic solvent like pentane/dichloromethane by using the fuimel-separator or rotation-perforator method over a longer period. The extract is dried and concentrated by solvent evaporation. The concentrated extract can be applied to GC-analysis. This method is applicable for liquid extracts and flavouring compounds [4]. 

This technique is the most commonly used chromatographic method for analysis of volatile flavouring compounds. 

Most flavourings are complex mixtures of many compounds. As IRMS makes only sense with pure analytes, a strict purification of individual substances is indispensable. Therefore GC-IRMS has been further developed and optimised to multi-compound isotope ratio analysis by its coupling IRMS to capillary (c) and multidimensional (MD) gas chromatography (see 6.2.2.2.2). This methodology demands a strict intrinsic control and standardisation [340] apart from the international standards (see Table 6.3) also secondary standards like the polyethylene foil IAEA-CH7 or the NBS22 oil are available from the IAEA in Vieima. However, as these substances are also not suitable for the direct standardisation of data from a coupled GC system for flavour isotope analysis, certificated tertiary laboratory standards for hydrogen have been developed by parallel analysis of flavour compounds by TC/EA-IRMS and MDGC-P-IRMS [210]. 

Isotope ratio measurements entered quality control of flavouring compounds about 20 years ago, and today this methodology has been established as a routine test in a number of laboratories. The special field and the potential for isotope analysis is authenticity identification of flavourings and their components, mainly with regard to the differentiation between natural and nature-identical or synthetic products and to their assignment to botanical and climatic origins. To this end isotope analysis completes and enlarges the quality information provided by classic methods. 

First success in enantioselective flavouring analysis was achieved by chromatographic separations of diastereomeric derivatives. In spite of limited sensitivity and frequently laborious work-up conditions, these methods revealed reliable insight into enantiomeric distribution of y(5) lactones and other chiral fruit flavouring compounds, as reviewed previously [55]. 

Enantio-IRMS also offers a direct method to detect conclusively a blend of enantio-pure chiral flavour compounds with synthetic racemates. An origin-specific enantiomeric ratio may be imitated but not yet detectable, neither by enantioselective analysis nor by IRMS-measurements. However, in the case of enantio-IRMS a simulated origin-specific enantiomeric distribution is proved by different 5 C-levels of the detected enantiomers. 

A. Mosandl, A. Kustermann, U. Palm, H.-P. Dorau and W.A. Konig. Stereoisomeric flavour compounds XXVIII Direct chirospecific HRGC-analysis of natural y-lactones. Z. Lebensm. Unters. Forsch., IM, 517-520 (1989). 

V. Karl, A. Dietrich and A. Mosandl. Stereoisomeric Flavour Compounds LXIV The chirospecific analysis of 2-alkyl-branched flavour compounds from headspace extracts and their sensory evaluation. Phytochem. Anal., 4, 158-164 (1993). 

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