Comparison and integration of analytical methods for the characterization of vanilla chemistry

There is a need for an analytical method to establish a universal criterion for quality of cured vanilla bean. The chemistry of vanilla, one the world’s most popular flavors is extremely complex. As such, no single analytical technique can fully characterize it. Commercially, vanilla is analyzed for many reasons including flavor/aroma quality, authenticity, geographic sourcing, concentration of vanillin and other major components, adulteration, contamination and quality defects. Furthermore, vanilla for analysis may be present in various forms such as alcoholic extracts or whole beans which present analytical challenges. In this research an integrated analytical approach was used for the analysis of whole beans and extracts which spanned volatile and semi-volatile components. An improved high pressure liquid chromatography (HPLC) analytical method was developed for routine analysis of vanillin and other phenolics in vanilla extracts resulting in lowered costs, greatly reduced analysis time and reduced solvent usage. A series of headspace concentration techniques including solid phase microextraction (SPME), headspace sorptive extraction (HSSE) and dynamic headspace were used to pinpoint a common sour, fermented off-odor quality defect in commercial Bourbon vanilla beans. Indicator compounds for microbial fermentation including fusel oil, microbial transformation products and depletion of flavor precursors were identified. Each headspace method has its own advantages and disadvantages. The sensitivity and selectivity of each method was manipulated to reveal individual clues of the off-odor. The combination of all three techniques gave detailed insight into the source of the defect. An improved direct thermal desorption gas chromatography mass spectrometry (DTD-GC-MS) method was developed to enhance resolution. Vanilla beans from Tanzania were analyzed for the first time using the improved DTD-GC-MS method and were found to contain very high concentrations of vanillin. Additionally, analysis of Bourbon, Indonesian, Ugandan, and Tahitian vanilla beans by the new DTD-GC-MS method revealed several new compounds in each that were not previously reported. Several novel compounds identified in a wild type vanilla bean previously by DTD-GC-MS including anisyl anistate, anisyl myristate and anisyl palmitate were synthesized to confirm the structure and GC-O was employed to evaluate their sensory properties.Ph. D.Includes bibliographical referencesby Stephen J. Tot