Vanillin

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Vanillin
IUPAC name 4-Hydroxy-3-methoxybenzaldehyde
Other names Vanilin
Vanillic aldehyde
Methyl vanillin
Identifiers
3D model (JSmol)
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RTECS number YW5775000
Properties
C8H8O3
Molar mass 152.15 g/mol
Appearance White or lightly yellow solid
(usually in needles)
Density 1.056 g/cm³, solid
Melting point
Boiling point
Viscosity ? cP at ?°C
Hazards
Main hazards May cause irritation to skin,
eyes, and respiratory tract
R-phrases R22.
S-phrases S24/25.
Flash point {{{value}}}
Related compounds
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

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 is used as a flavoring agent in foods, beverages, and pharmaceuticals.

Methyl vanillin is used by the food industry as well as ethyl vanillin. The ethyl is more expensive but has a stronger note, and differs 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 the petrochemical guaiacol, or from lignin, a natural 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.[1]

History

Vanilla was cultivated as a flavoring by pre-Columbian Mesoamerican peoples; at the time of their conquest by Hernándo Cortés, the Aztecs used it as a flavoring for chocolate. Europeans became aware of both chocolate and vanilla around the year 1520.[2]

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.[3] 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,[4] and in 1876, Karl Reimer synthesized vanillin from guaiacol.[5] By the late 19th century, semisynthetic vanillin derived from the eugenol found in clove oil was commercially available.[6]

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 Kraft 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.[7] 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.[8]

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.[9] However, unlike vanillin synthesized from lignin or guaiacol, it can be labeled as a natural flavoring.

Occurrence

Vanillin is most prominent as the principal flavor and aroma compound in vanilla. Cured vanilla pods contain approximately 2% by dry weight vanillin; on cured pods of high quality, relatively pure vanillin may be visible as a white dust or "frost" on the exterior of the pod.

At smaller concentrations, vanillin contributes to the flavor and aroma profiles of foodstuffs as diverse as olive oil,[10] butter,[11] and raspberry[12] and lychee[13] fruits. Aging in oak barrels imparts vanillin to some wines and spirits.[14] In other foods, heat treatment evolves vanillin from other chemicals. In this way, vanillin contributes to the flavor and aroma of coffee,[15] maple syrup,[16] and whole grain products including corn tortillas[17] and oatmeal.[18]

Production

File:Vanilla fragrans 2.jpg
These green seed pods contain vanillin only in its glycoside form, and lack the characteristic odor of vanilla.

Natural production

Natural vanillin is extracted from the seed pods of Vanilla planifola, a vining orchid native to Mexico, but now grown in tropical areas around the globe. Madagascar is presently the largest producer of natural vanillin.

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.[19] 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,[20] 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.

Chemical synthesis

The demand for vanilla flavoring has long exceeded the supply of vanilla beans. As of 2001, the annual demand for vanillin was 12,000 tons, but only 1800 tons of natural vanillin were produced.[21] The remainder was produced by chemical synthesis. Vanillin was first synthesized from eugenol (found in oil of clove) in 1874–75, less than 20 years after it was first identified and isolated. Vanillin was commercially produced from eugenol until the 1920s.[22] Later it was synthesized from lignin-containing sulfite liquor, a byproduct of wood pulp processing in paper manufacture.[23] Counter-intuitively, even though it uses waste materials, the lignin process is no longer popular because of environmental concerns, and today most vanillin is produced from the petrochemical raw material guaiacol.[24] Several routes exist for synthesizing vanillin from guaiacol.[25] At present, the most significant of these is the two-step process practiced by Rhodia since the 1970s, in which guaiacol reacts with glyoxylic acid by electrophilic aromatic substitution. The resulting vanilmandelic acid is then converted to vanillin by oxidative decarboxylation.[26]

Uses

The largest single use of vanillin is as a flavoring, usually in sweet foods. The ice cream and chocolate industries together comprise 75% of the market for vanillin as a flavoring, with smaller amounts being used in confections and baked goods.[27]

Vanillin is also used in the fragrance industry, in perfumes, and to mask unpleasant odors or tastes in medicines, livestock fodder, and cleaning products.[28]

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,[29] but as of 2004 this use accounts for only 13% of the market for vanillin.[30]

References

  • Adahchour, Mohamed (1999). "Trace-level determination of polar flavour compounds in butter by solid-phase extraction and gas chromatography–mass spectrometry". Journal of Chromatography A. 844 (1–2): 295–305. doi:10.1016/S0021-9673(99)00351-9. Unknown parameter |coauthors= ignored (help)
  • Blank, Imre (1992). "Potent odorants of the roasted powder and brew of Arabica coffee". Zeitschrift für Lebensmittel-Untersuchung und -Forschung A. 195 (3): 239–245. doi:10.1007/BF01202802. Unknown parameter |coauthors= ignored (help)
  • Brenes, Manuel (1999). "Phenolic Compounds in Spanish Olive Oils". Journal of Agricultural and Food Chemistry. 47 (9): 3535–3540. doi:10.1021/jf990009o. Unknown parameter |coauthors= ignored (help)
  • Buttery, Ron G. (1995). "Volatile Flavor Components of Corn Tortillas and Related Products". Journal of Agricultural and Food Chemistry. 43 (7): 1878–1882. doi:10.1021/jf00055a023. Unknown parameter |coauthors= ignored (help)
  • Dignum, Mark J. W. (2001). "Vanilla Production: Technological, Chemical, and Biosynthetic Aspects". Food Reviews International. 17 (2): 119–120. doi:10.1081/FRI-100000269. Retrieved 2006-09-09. Unknown parameter |coauthors= ignored (help)
  • Esposito, Lawrence J. (1997). "Vanillin". Kirk-Othmer Encyclopedia of Chemical Technology, 4th edition. 24. New York: John Wiley & Sons. pp. 812–825. Unknown parameter |coauthors= ignored (help)
  • Fund for Research into Industrial Development, Growth and Equity (FRIDGE) (2004). Study into the Establishment of an Aroma and Fragrance Fine Chemicals Value Chain in South Africa, Part Three: Aroma Chemicals Derived from Petrochemical Feedstocks. National Economic Development and Labor Council.
  • Gobley, N.-T. (1858). "Recherches sur le principe odorant de la vanille". Journal de Pharmacie et de Chimie. 34: 401–405.
  • Guth, Helmut (1995). "Odorants of extrusion products of oat meal: Changes during storage". Zeitschrift für Lebensmittel-Untersuchung und -Forschung A. 196 (1): 22–28. doi:10.1007/BF01192979. Unknown parameter |coauthors= ignored (help)
  • Hocking, Martin B. (1997). "Vanillin: Synthetic Flavoring from Spent Sulfite Liquor" (PDF). Journal of Chemical Education. 74 (9): 1055. Retrieved 2006-09-09. Unknown parameter |month= ignored (help)
  • Kermasha, S. (1995). "Determination of Phenolic Compound Profiles in Maple Products by High-Performance Liquid Chromatography". Journal of Agricultural and Food Chemistry. 43 (3): 708–716. doi:10.1021/jf00051a028. Unknown parameter |coauthors= ignored (help)
  • Lampman, Gary M. (1977). "Preparation of vanillin from eugenol and sawdust". Journal of Chemical Education. 54 (12): 776–778. Unknown parameter |coauthors= ignored (help)
  • Ong, Peter K. C. (1998). "Gas Chromatography/Olfactory Analysis of Lychee (Litchi chinesis Sonn.)". Journal of Agricultural and Food Chemistry. 46 (6): 2282–2286. doi:10.1021/jf9801318. Unknown parameter |coauthors= ignored (help)
  • Reimer, K. (1876). "Ueber eine neue Bildungsweise aromatischer Aldehyde". Berichte der deutschen chemischen Gesellschaft. 9 (1): 423–424. doi:10.1002/cber.187600901134.
  • Roberts, Deborah D. (1996). "Effects of Heating and Cream Addition on Fresh Raspberry Aroma Using a Retronasal Aroma Simulator and Gas Chromatography Olfactometry". Journal of Agricultural and Food Chemistry. 44 (12): 3919–3925. doi:10.1021/jf950701t. Unknown parameter |coauthors= ignored (help)
  • Rouhi, A. Maureen (2003). "Fine Chemicals Firms Enable Flavor And Fragrance Industry". Chemical and Engineering News. 81 (28): 54.
  • Tiemann, Ferd. "Ueber das Coniferin und seine Umwandlung in das aromatische Princip der Vanille". Berichte der Deutschen Chemischen Gesellschaft. 7 (1): 608–623. doi:10.1002/cber.187400701193. Unknown parameter |coauthors= ignored (help)
  • Van Ness, J. H. (1983). "Vanillin". Kirk-Othmer Encyclopedia of Chemical Technology, 3rd edition. 23. New York: John Wiley & Sons. pp. 704–717.
  • Viriot, Carole (1993). "Ellagitannins and lignins in aging of spirits in oak barrels". Journal of Agricultural and Food Chemistry. 41 (11): 1872–1879. doi:10.1021/jf00035a013. Unknown parameter |coauthors= ignored (help)
  • Walton, Nicholas J. (2003). "Vanillin". Phytochemistry. 63 (5): 505–515. doi:10.1016/S0031-9422(03)00149-3. Unknown parameter |coauthors= ignored (help); Unknown parameter |month= ignored (help)

References

  1. According to Esposito 1997, blind taste-testing panels cannot distinguish between the flavors of synthetic vanillin from lignin and from guaicol, but can distinguish the odors of these two types of synthetic vanilla extracts. Guaiacol vanillin, adulterated with acetovanillone, has an odor indistinguishable from lignin vanillin.
  2. Esposito 1997
  3. Gobley 1858
  4. Tiemann 1874
  5. Reimer 1876
  6. According to Hocking 1997, synthetic vanillin was sold commercially in 1874, the same year Tiemann and Haarmann's original synthesis was published. Haarmann & Reimer, one of the corporate ancestors of the modern flavor and aroma manufacturer Symrise, was in fact established in 1874. However, Esposito 1997 claims that synthetic vanillin first became available in 1894 when Rhône-Poulenc (since 1998, Rhodia) entered the vanillin business. If the former claim is correct, the authors of the latter article, being employees of Rhône-Poulenc, may have been unaware of any previous vanillin manufacture.
  7. Hocking 1997
  8. Esposito 1997
  9. Rouhi 2003
  10. Brenes 1999
  11. Adahchour 1999
  12. Roberts 1996
  13. Ong 1998
  14. Viriot 1993
  15. Blank 1992
  16. Kermasha 1995
  17. Buttery 1995
  18. Guth 1993
  19. Walton 2003
  20. Dignum 2001 reviews several such proposed innovations in vanilla processing, including processes in which the seed pods are chopped, frozen, warmed by a heat source other than the sun, or crushed and treated by various enzymes. Whether or not these procedures produce a product whose taste is comparable to traditionally prepared natural vanilla, many of them are incompatible with the customs of the natural vanilla market, in which the vanilla beans are sold whole, and graded by, among other factors, their length.
  21. Dignum 2001
  22. Hocking 1997. This chemical process can be conveniently carried out on the laboratory scale using the procedure described by Lampman 1977.
  23. Hocking 1997
  24. Hocking 1997
  25. Van Ness 1983
  26. Esposito 1997
  27. FRIDGE 2004, p. 33
  28. Esposito 1997
  29. Hocking 1997
  30. FRIDGE 2004, p. 32

External links

cs:Vanilin da:Vanillin de:Vanillin it:Vanillina he:ונילין nl:Vanilline sv:Vanillin th:วานิลลิน



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