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Analysis of Odourant Compounds in Wine - with Headspace Solid-Phase Microextraction and Gas Chromatography- Mass Spectrometry

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Analysis of Odourant Compounds in Wine - with Headspace Solid-Phase Microextraction and Gas Chromatography- Mass Spectrometry Analysis of odourant compounds in wine - With headspace solid-phase microextraction and gas chromatography- mass spectrometry By Emma Ödmar Analytical science program in chemistry with focus on forensics Candidate for Degree of Bachelor of Science School of Science and Technology Örebro university Spring term 2018 Table of contents Abstract .................................................................................................................................. 3 1. Introduction......................................................................................................................... 4 1.1 Aim ............................................................................................................................... 4 1.2 Scope ............................................................................................................................. 4 1.3 Background ................................................................................................................... 4 1.3.1 Wine ....................................................................................................................... 4 1.3.2 Headspace solid-phase microextraction (HS-SPME)................................................ 5 1.3.3 Gas chromatography-mass spectrometry (GC-MS) .................................................. 6 2. Materials and methods......................................................................................................... 7 2.1 Materials........................................................................................................................ 7 2.1.1 Chemicals ............................................................................................................... 7 2.1.2 Samples ................................................................................................................... 8 2.1.3 Sample preparation .................................................................................................. 9 2.1.4 Standard compounds ..............................................................................................10 2.2 Methods ........................................................................................................................11 2.2.1 Headspace solid-phase microextraction ..................................................................11 2.2.2 Gas chromatography-mass spectrometry.................................................................12 2.2.3 Method issues .........................................................................................................13 3. Results ...............................................................................................................................14 3.1 Artificial wine standard .................................................................................................14 3.2 Wine analysis result ......................................................................................................15 3.2.1 White wines ...........................................................................................................15 3.2.2 Orange wines .........................................................................................................18 3.2.3 Red wines ...............................................................................................................19 3.2.4 Sparkling wines ......................................................................................................24 3.3 Quantification ...............................................................................................................25 3.4 Identified compounds ....................................................................................................25 3.5 Statistics .......................................................................................................................26 4. Discussion ..........................................................................................................................27 4.1 Limitations ...................................................................................................................27 4.2 Quantitative analysis .....................................................................................................27 1 4.3 Aroma compounds ........................................................................................................28 4.5 Comparison of wines ....................................................................................................29 4.5.1 White wines ...........................................................................................................29 4.5.2 Orange wines .........................................................................................................30 4.5.3 Red wines ...............................................................................................................30 4.5.4 Sparkling wines ......................................................................................................30 5. Conclusion .........................................................................................................................30 6. References .........................................................................................................................32 7. Appendix ...........................................................................................................................34 2 Abstract Wine is a drink that can enhance the flavour experience of food, which is why it is important that the wine’s sensory profile is explained correctly to the consumers. In this study, headspace solid-phase microextraction gas chromatography mass spectrometry was used to characterise odourant compounds in wine to find chemical markers to explain wine sensory profiles instead of sensory analysis. The study included 16 different wines, red, white, orange and sparkling, where the nine most abundant peaks in each wine sample were evaluated. Homologue patterns based on areas were used to compare profiles between different wines. When studying homologue patterns for each wine and comparing within wine groups, differences and similarities can be seen. All wine samples contained isoamyl alcohol and the majority of them also contained ethyl decanoate, octanoic acid and decanoic acid. Six out of eight red wines contained ethyl succinate and five of them also contained ethyl hexanoate. All white wine samples showed presence of ethyl octanoate and ethyl hexanoate. The orange wines also contained ethyl octanoate and ethyl hexanoate, along with pentanoic acid. Both sparkling wines contained ethyl octanoate and ethyl hexanoate in addition with phenylethyl alcohol. However, a more thorough study covering more compounds to identify the less obvious differences of wine would have to be performed for a more precise explanation of the wine’s characterisation and sensory profile. It should be noted that the method of this study does leave room for improvements to improve the quality of the results. For example, since the most abundant compounds are not necessarily the ones with the most powerful odours, quantification based on response of an internal standard would strengthen the study. Additional compounds in the samples could also be further investigated. Statistically the method would also need improvement for satisfactory results regarding reproducibility of the samples. 3 1. Introduction 1.1 Aim A current problem in Sweden is the large volume of destruction of wine that has a deviant sensory profile than what was intended. By combining chemical characterisation and sensory analysis it would be possible to re-label these wines with an appropriate label. Combining this with recommendations of suitable food for the new correct profile the wines could be sold in the stores instead of being sent to destruction. The aim in this project is to find chemical markers that can be connected to certain sensory profiles, so that chemical profiling could be used instead of sensory analysis for new profiling of wines, with the goal to reduce the large volumes of wine sent to destruction. 1.2 Scope This project is a part of a larger study and covers the gas chromatography analysis of volatile odourant compounds in wine samples. Liquid chromatography of the same samples will also be performed but will not be included in this project. This and sensory analysis could be used for comparison of results within the study. 1.3 Background 1.3.1 Wine Wine is a very popular drink that has been produced for thousands of years (1). Wine is obtained when fermenting grape must and reflects a distinguishable flavour. Originally, wine was only produced in Europe, by the Romans and the Greeks, but now the production has spread all over the world where the climate is suitable. Wine is usually appreciated combined with food as it enhances the flavour experience and is also a social phenomenon. Chemically, wine consists of non-volatile tastants, such as phenolic compounds, and volatile aroma compound, such as phenolic acids (1, 2). The aroma is complex because the aroma compounds have different origins (1). The compounds can be found in different places such as the grape itself, produced during grape processing, alcoholic fermentation and during maturation of the wine. Consumers need correct description of the product that they are purchasing, but traditional descriptive methods are time demanding (3). There is also issues with vocabulary use to
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