Handbook of Vanilla Science and Technology

A significant review of vanilla flavor research is found in the 1991 Encyclopedia of Food Science & Technology, which covers vanilla flavor analyses up to that time fairly extensively.

In 1992 and 1993, researchers at Rutgers University used direct thermal desorption-gas chromatography (DTD-GC) and thermal desorption-gas chromatography-mass spectrometry (DTD-GC-MS) methodologies and identified 60 flavor compounds among 10 vanilla bean samples of different origin (Hartman et al. 1992; Adedeji etal. 1993). Several of the compounds were identified in vanilla for the first time. The phenols identified in Bourbon vanilla were suggested to be used as flavor quality indicators. These investigations identified a wide variety of constituents, which contribute to the “characteristic” flavor and aroma, mostly aldehydes, ketones, acids, alcohols, esters, ethers, and long and short chain hydrocarbons.

Taylor (1993), from the Natural Resources Institute, developed an HPLC procedure capable of separating 40 constituents of vanilla extracts. Various method conditions were investigated and retention times and wavelength absorbencies for the constituents were reported. However, this effort focused on the quantitation of the four main vanilla constituents for which regression equations had greater than 0.99 correlation coefficients and a small comparison was made between HPLC and the ISO 5565:1982 (withdrawn in 1999 and replaced) spectrophometric method.

Hydroxymethylfurfural (HMF) was identified as a minor constituent of vanilla extracts after isolation by liquid-liquid extraction and column chromatography, followed by a thin layer chromatographic method. Typical HMF concentrations ranged from 0.2 to 34 mg/100 mL using a rapid test amendable to any laboratory (Kiridena et al. 1994). German researchers (Ehlers et al. 1994) compared V. tahitensis and V. planifolia extracts by HPLC analyses. The Tahitian beans had low levels of vanillin and vanillic acid and relatively high quantities of p-hydroxybenzaldehyde. These beans also had significant levels of anisic acid and anisyl alcohol imparting a unique flavor to this product. In addition, they indicated that piperonal was probably not a natural constituent of vanilla, as had been thought previously.

Gas chromatography-olfactometry (GC-O) was applied by US researchers (Yang and Peppard 1996) “to bridge the gap between instrument analysis and sensory perception.” They used an “odor intensity technique” (OSME) of GC-O to explore the origin of the “beany notes” in vanilla extract. Perez-Silva et al. (2006) used GC-MS and GC-O to identify 65 vanilla volatiles in a pentane/ether extract of vanilla beans. Sensory analysis showed this extract to be the most representative of vanilla beans. GC-O revealed 26 odor active compounds and that guaiacol, 4-methylguaiacol, acetovanillin, and vanillyl alcohol, although found in much lower concentrations then vanillin, are as intense.

Ramaroson-Raonizafinimanana et al. (1999), from France, analyzed the neutral lipids from V fragrans (an older name for V. planifolia) and V. tahitensis, which resulted in the identification of a new product family, long chain g-pyrones. Three g-pyrones were identified and their variability studied in relation to bean maturity. They proposed that the pyrones may have anti-inflammatory and potential anti-platelet effects. The next year this group again isolated and identified an additional product family, b-dicarbonyl compounds (Ramaroson-Raonizafinimanana et al. 2000). The most abundant was nervonoylacetone, representing 74.5% of this fraction. These constituents like the g-pyrones, were studied in relation to bean maturity. The b-dicarbonyl family was found in the beans of the aromatic species V. fragrans and V. tahitensis, but not in V. madagascariensis, which produces non-aromatic beans.

Australian researchers (Sostaric et al. 2000) developed a solid-phase micro-extraction (SPME) method coupled with GC-MS and used it to profile vanilla extracts. An evaluation of several fibers and analytical conditions was undertaken. Poly (acrylate) was identified as the best fiber. Their analysis was able to distinguish among three vanilla extracts, a Bourbon, Tahitian, and an Indonesian. The extract of Tahitian vanilla was unique in the presence of p-methoxybenzaldehyde (anisaldehyde) and an unidentified component. Bourbon and Indonesian extracts could be distinguished by the quantities of hexanoic acid, 5-propenyl-1, 3-benzodioxole, and ethyl nonanoate. They proposed the use of this method for identifying adulterated products as well as indicating that this method had the potential to be used to identify the type of vanilla extract or flavoring used to flavor foods.