Innovative Process Technologies - Catch me if you can: Analysis of volatile aroma compounds with GC-MS

eFOODLab_International_03_2014

Catch me if you can Analysis of volatile compounds with Tenax®, TwisterTM, SPME and MonoTrapTM Aroma compounds are affecting the character and quality of food. Recent advances in analytical methods and tools have led to intensive research in discovering and clarifying the role of volatile compounds in food products. Besides, analytical tools have greatly contributed to the understanding of plant-environment interactions. The combination with software solutions enables not only the identification of the key compounds involved in these interactions but also their mapping in physiological pathways. Sampling In addition to classical extraction methods involving organic solvents such as steam distillation or SDE (simultaneous distillation-extraction) various methods have been developed to analyse samples without the utilization of organic solvents. With regards to head-space sampling, Tenax®-traps were firstly used. A clean air stream is directed to the trap containing porous material, the latter retaining the volatile compounds. SPME (Solid Phase Micro Extraction) can alternatively be used for direct sampling (Figure 1A). These devices harbour different type of materials such as Carbowax, Polydivinylbenzol, Carboxen and Polydimethylsiloxane (PDMS). Besides, different coating thicknesses are available. As a consequence, these devices allow a rapid and easy 6 3/14 eFOOD-Lab international Our Authors: Audrey Errard (left photo), Susanne Baldermann (right photo) Baldermann@igzev.de, Jun.-Prof. Dr. Susanne Baldermann, Leibniz-Institute of Vegetable and Ornamental Crops Großbeeren-Erfurt e.V., Theordor-Echtermeyer-Weg 1, 14979 Großbeeren, Tel. +49 (0)3371-78241, Fax +49 (0)33701-55391 Fig. 1: A) Study of the biotransformation of β-ionone to dihydro-β- ionone in roses with SPME, B) Study of flavour compounds in aqueous solution and headspace sampling with TwistersTM , C) Analysis of volatiles emitted from flower tissues with MonoTrapTM sampling. Due to the equilibrium state formed during the sampling several parameters must remain constant throughout the extraction for accurate quantification. These include the amount of sample material, the temperature and the sampling duration. SPME devices are currently used in diverse fields of research such as food chemistry, environmental sciences, toxicology and forensics. Another rapid technic requiring minimal sample preparation to analyse volatile organic compounds in aqueous solutions (eg. beverage) is Stir Bar Sorptive Extraction (SBSE TwisterTM). This technique has the same requirements as SPME. Hence, SPME and SBSE utilisation overlaps in some fields of research. Apart from aqueous samples, the TwisterTM can be used for head-space sampling (Fig. 1 B). In general the TwisterTM is more sensitive due to a thicker coating (about 100 fold in comparison with SPME). With SPME however, the polarity range is broader due to different coating materials. Finally, MonoTrapTM (Monolithic Material Sorption Extraction, MMSE) can be also used to sample volatile and semi-volatile compounds (Fig. 1C). The specific structure of the spores and mesospores provides the necessary sampling surface area and therefore increases the trapping capacity of this material. Currently, ODS and activated charcoal based materials are available and can be used as alternative head-space sampling. Analysis Specific thermo desorption procedures are required to analyse the metabolites 1-11. From monolithic material the volatiles are released by organic solvents (eg. Dichloromethan). It is known that the GC-MS is the most efficient method to separate, identify and quantify volatile compounds. In this case, the choice of the column is of prime importance. To analyse complex blends of metabolites by chromatography, the use of multidimensional GC/GC systems is possible. To separate chiral compounds, the use of chiral columns is necessary. Volatile chiral compounds are frequently found in biological samples and commonly exhibit different flavour properties and biological activities. To improve sensitivity of mass spectrometry (MS), the GC can be coupled to quadrupoles or triquadrupoles. Such coupling techniques provide the advantage of lower detection and quantification limits especially for metabolites in complex matrices. Regarding the im- Innovative Processi ng Tech nologies


eFOODLab_International_03_2014
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