Vanillin, methyl vanillin, or 4-hydroxy-3-methoxybenzaldehyde, is an organic compound with the molecular formula C8H8O3. Its functional groups include aldehyde, ether and phenol. It is the primary component of the extract of the vanilla bean. Synthetic vanillin, instead of natural vanilla extract, is sometimes used as a flavoring agent in foods, beverages, and pharmaceuticals.
Methyl vanillin is used by the food industry as well as ethylvanillin. The ethyl is more expensive but has a stronger note. It differs from vanillin by having an ethoxy group (-O-CH2CH3) instead of a methoxy group (-O-CH3).
Natural "vanilla extract" is a mixture of several hundred different compounds in addition to vanillin. Artificial vanilla flavoring is a solution of pure vanillin, usually of synthetic origin. Because of the scarcity and expense of natural vanilla extract, there has long been interest in the synthetic preparation of its predominant component. The first commercial synthesis of vanillin began with the more readily available natural compound eugenol. Today, artificial vanillin is made from either guaiacol or from lignin, a constituent of wood which is a byproduct of the paper industry.
Lignin-based artificial vanilla flavoring is alleged to have a richer flavor profile than oil-based flavoring; the difference is due to the presence of acetovanillone in the lignin-derived product, an impurity not found in vanillin synthesized from guaiacol.
Vanillin was first isolated as a relatively pure substance in 1858 by Nicolas-Theodore Gobley, who obtained it by evaporating a vanilla extract to dryness, and recrystallizing the resulting solids from hot water. In 1874, the German scientists Ferdinand Tiemann and Wilhelm Haarmann deduced its chemical structure, at the same time finding a synthesis for vanillin from coniferin, a glycoside of isoeugenol found in pine bark. Tiemann and Haarmann founded a company, Haarmann & Reimer (now part of Symrise) and started the first industrial production of Vanillin using their process in Holzminden (Germany). In 1876, Karl Reimer synthesized vanillin from guaiacol. By the late 19th century, semisynthetic vanillin derived from the eugenol found in clove oil was commercially available.
Synthetic vanillin became significantly more available in the 1930s, when production from clove oil was supplanted by production from the lignin-containing waste produced by the Sulfite pulping process for preparing wood pulp for the paper industry. By 1981, a single pulp and paper mill in Ontario supplied 60% of the world market for synthetic vanillin. However, subsequent developments in the wood pulp industry have made its lignin wastes less attractive as a raw material for vanillin synthesis. While some vanillin is still made from lignin wastes, most synthetic vanillin is today synthesized in a two-step process from the petrochemical precursors guaiacol and glyoxylic acid.
Beginning in 2000, Rhodia began marketing biosynthetic vanillin prepared by the action of microorganisms on ferulic acid extracted from rice bran. At $700/kg, this product, sold under the trademarked name Rhovanil Natural, is not cost-competitive with petrochemical vanillin, which sells for around $15/kg. However, unlike vanillin synthesized from lignin or guaiacol, it can be labeled as a natural flavoring.
At lower concentrations, vanillin contributes to the flavor and aroma profiles of foodstuffs as diverse as olive oil, butter, raspberry and lychee fruits. Aging in oak (wine) barrels imparts vanillin to some wines and spirits. In other foods, heat treatment evolves vanillin from other chemicals. In this way, vanillin contributes to the flavor and aroma of coffee, maple syrup, and whole grain products including corn tortillas and oatmeal.
As harvested, the green seed pods contain vanillin in the form of its β-D-glycoside; the green pods do not have the flavor or odor of vanilla. After being harvested, their flavor is developed by a months-long curing process, the details of which vary among vanilla-producing regions, but in broad terms it proceeds as follows:
First, the seed pods are blanched in hot water, to arrest the processes of the living plant tissues. Then, for 1–2 weeks, the pods are alternately sunned and sweated: during the day, they are laid out in the sun, and each night, wrapped in cloth and packed in airtight boxes to sweat. During this process, the pods become a dark brown, and enzymes in the pod release vanillin as the free molecule. Finally, the pods are dried and further aged for several months, during which time their flavors further develop. Several methods have been described for curing vanilla in days rather than months, although they have not been widely developed in the natural vanilla industry, with its focus on producing a premium product by established methods, rather than on innovations that might alter the product's flavor profile.
Vanillin accounts for about 2% of the dry weight of cured vanilla beans, and is the chief among about 200 other flavor compounds found in vanilla.
Vanillin has been used as a chemical intermediate in the production of pharmaceuticals and other fine chemicals. In 1970, more than half the world's vanillin production was used in the synthesis of other chemicals, but as of 2004 this use accounts for only 13% of the market for vanillin.
Additionally, vanillin can be used as a general purpose stain for developing thin layer chromatography (TLC) plates to aid in visualizing components of a reaction mixture. This stain yields a range of colors for these different components.
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