Handbook of Vanilla Science and Technology

Vanilla flavor is often described by the layperson as being “plain” and unremarkable. However, specialists involved in the vanilla industry and flavorists or perfumers who appreciate the unique qualities vanilla brings to their creations know that vanilla flavor is extremely complex and far from “plain”. Just like a fine wine, vanilla flavor is an orchestra of individual nuances that combine to form the unique bouquet we know as vanilla. Although the compound 3-methoxy-4-hydroxybenzaldehyde (vanillin) is characterizing for vanilla, it alone does not constitute vanilla flavor. Indeed, sensory evaluation of pure synthetic vanillin or the similar compound, 3-ethoxy-4-hydroxybenzaldehyde (ethyl vanillin), which are often used for synthetic imitation vanilla renditions, both are found to possess a lack-luster vanillalike odor with a somewhat “chemical-like” nuance. The characterizing notes of vanillin must be accompanied by other compounds to produce the familiar flavor and aroma we know as vanilla. Indeed, in some cases, extracts with high amounts of vanillin will not taste as good as other extracts with lower vanillin content but containing the other flavor components. Flavor chemists call these additional compounds vanilla fortifiers or synergists. The following is a lexicon of aroma and flavor descriptors that sensory evaluators often use to grade vanilla.

11.1 LEXICON OF VANILLA AROMA/FLAVOR DESCRIPTORS

Acidic, Anisic, Aromatic, Balsamic, Barnyard, Caramelized, Chocolate, Creamy, Earthy, Floral, Fruity, Hay-like, Moldy, Musty, Phenolic, Prune, Pungent, Raisin, Resinous, Rummy, Smokey, Sour, Spicy, Sweet, Tea-like, Tobacco-like, Vanillin, Vinegar, Woody

As can be seen from this list of descriptors, vanilla flavor is not “plain” but rather complex and intriguing. Volatile and semi-volatile compounds other than vanillin that are found in vanilla extracts are responsible for many of these sensory attributes and a compilation of these many compounds is the focus of this chapter.

Vanilla renders different flavor and aroma profiles, depending on geographic growing region, cultivation methods, curing, extraction, or storage conditions. The flavor and aroma qualities undergo a constant transition as the initially flavorless green vanilla beans are cured and used directly or extracted with water and ethanol to produce vanilla extract. Reactions occurring in the bean curing process are largely enzymatic and involve conversion of nonvolatile, glycosidically-bound phenolic precursor molecules such as glucovanillin into the free forms (Walton et al. 2003; Havkin-Frenkel et al. 2004, 2005; Korthou and Verpoorte 2007). In addition, many compounds present in cured vanilla beans are further chemically transformed into different compounds as they react with ethanol in the vanilla extraction process. Pungent acids can be converted into ethyl esters with more pleasant floral and fruity aromas. Esters originally present in beans can convert into acids or alcohols. Many esters originally present as methyl esters in beans can trans-esterify into corresponding ethyl esters in the extract process. Aldehydes can be converted into more delicate acetals, which have potential to revert back when exposed to higher water concentration in downstream applications. Finally, when vanilla is used in different foods, it renders different flavor profiles. Vanillin is an aromatic aldehyde and it readily reacts with amino groups of proteins and amino acids to form resonance-stabilized, Schiff-base compounds that often attenuate its flavor impact. Frozen desert manufacturers that tried to lower calories by substituting textured proteins for milk fat learned this the hard way. Similar reaction pathways produce colored compounds that limit vanillin use in perfumery. Vanilla is actually a versatile and dynamic flavoring substance, the potential of which has still not been fully realized.

Vanilla flavor begins with the vanilla bean. The vanilla bean is the sole edible fruit of the orchid family. Out of 110 known Vanilla species only two, Vanilla planifolia Andrews and Vanilla tahitensis Moore, are allowed to be used in foods. The estimated world production of vanilla beans is around 2,000 tons per year (Havkin-Frenkel et al. 2005). Most of the growing areas, notably Madagascar, cultivate V. planifolia, while Tahiti, Papua New Guinea (PNG), and limited parts of Indonesia produce mainly V. tahitensis. Mesoamerica is known as the origin of V. planifolia but the origin of V. tahitensis was only recently been determined and appears to be a hybrid of V. planifolia and V. odorata (Lubinsky et al. 2008). Novel compounds described for the first time in this chapter appear to support this conclusion.