Vanillin

OVERVIEW

Vanillin is a white crystalline solid with a pleasant, sweet aroma, and a characteristic vanilla-like flavor. Chemically, it is the methyl ether of 4-hydroxybenzoic acid, a ring compound that contains the carboxyl (-COOH) group and the hydroxyl (-OH) group. Vanillin is the substance responsible for the familiar taste of vanilla, which has been used as a food additive and spice for hundreds of years. Vanilla was probably first used as a flavoring by the inhabitants of South and Central America before the arrival of Europeans in the sixteenth century. Spanish explorers brought the spice back to Europe, where it soon became very popular as a food additive and for the flavoring of foods. Since that time, vanilla has become one of the world's most popular spices.

KEY FACTS

OTHER NAMES:

4-hydroxy-3-methoxybenzaldehyde; 3-methoxy-4-hydroxybenzaldehyde; vanillic aldehyde

FORMULA:

(CH₃O)(OH)C₆H₃CHO

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Ether (organic)

STATE:

Solid

MOLECULAR WEIGHT:

152.15 g/mol

MELTING POINT:

81.5°C (179°F)

BOILING POINT:

285°C (545°F)

SOLUBILITY:

Slightly soluble in water; soluble in glycerol, ethyl alcohol, ether, and acetone

HOW IT IS MADE

Vanilla is obtained naturally from the seed pod of the tropical orchid Vanilla planifolia by a lengthy and expensive process. The pods are picked before they ripen and then cured until they are dark brown. The curing process involves soaking the pods in hot water, sun-drying them, and allowing them to "sweat" in straw. The cured pods are then soaked in alcohol to produce a product known as pure vanilla extract. The primary constituent in pure vanilla extract is vanillin, which gives the product its flavor. The process of extracting pure vanilla from seed pods may take as long as nine months.

Some people prefer a vanilla product that contains no, or almost no, alcohol. If alcohol is removed, almost pure vanilla is left behind, leaving a product known as natural vanilla flavoring.

Vanilla can also be extracted from plants other than Vanilla planifolia, such as potato peels and pine tree sap. The most economical source of the product, however, is waste material left over from the wood pulp industry. That waste material consists primarily of lignin, a complex natural polymer that, along with cellulose, is the primary component of wood. The wastes from wood pulping can be treated to break down and separate the lignin. This leaves behind a complex mixture, a major component of which is vanilla. This vanilla is called lignin vanilla and has many of the same physical properties as natural vanilla. Since it is so much less expensive to make, it has become one of the major forms of vanilla used by consumers. Lignin vanilla is known commercially as artificial vanilla flavoring.

The two forms of vanilla described earlier—natural vanilla and lignin vanilla—are mixtures in which the compound vanillin is a major component. In both mixtures, other components are present in lesser amounts. These components may add somewhat different flavors and aromas, modifying the pure taste and smell of vanillin. Artificial methods for the production of pure vanillin have been available since the late 1890s. The most popular of those methods begins with eugenol ((C₃H₅)C₆H₃(OH)OCH₃) or isoeugenol ((CH₃CHCH)C₆H₃(OH)OCH₃). Either of these compounds is then treated with acetic anhydride ((CH₃CO)₂O) to obtain vanillin acetate, which is then converted to pure vanillin. The product of this reaction, unlike natural vanilla and lignin vanilla, is a pure compound, 4-hydroxy-3-methoxybenzaldehyde, pure vanillin. This method was the primary method for making artificial vanillin for more than 50 years. It has since been replaced by an alternative method of preparation, the Reimer-Tiemann reaction. This method for making artificial vanillin begins with catechol (C₆H₄(OH)₂) or guaiacol (CH₃OC₆H₄OH).

The Remier-Tiemann reaction is also used to produce another form of vanillin called ethyl vanillin. Ethyl vanillin is the ethyl ether of 4-hydroxybenzoic acid, 4-hydroxy-3-ethoxybenzaldehyde ((CH₃CH₂O)(OH)C₆H₃CHO). It is a close chemical relative of natural vanillin in which the methyl (-CH₃) group of natural vanillin is replaced by an ethyl (-CH₂CH₃) group. Ethyl vanillin is also known as artificial vanilla or synthetic vanilla. Its flavor is about three times as strong as that of methyl vanillin and is used to fortify or replace natural vanillin and lignin vanillin.

COMMON USES AND POTENTIAL HAZARDS

All forms of vanillin are used as a flavoring agent and sweetener in many types of foods, including candies, dessert products, ice creams, puddings, yogurts, diet shakes, and soft drinks. It is also added to some wines, alcoholic liquors, toothpastes, and cigarettes. The vanillins have also been shown to stimulate one's appetite, so they have been used to treat appetite loss. They are also added to cattle feed to enhance weight gain.

However, less than half the vanillin produced is used in food products. Vanillin's rich fragrance makes the compound useful also as an additive in perfumes, air fresheners, soaps, shampoos, candles, creams, lotions, colognes, and ointments. The compound is also used as a raw material in the manufacture of a variety of drugs, particularly the compound known as L-dopa, used to treat Parkinson's disease.

Interesting Facts

• The tropical orchid Vanilla planifolia is pollinated naturally by the tiny Melipone bee, native to Mexico. In areas where the bee does not live, the orchid must be pollinated artificially by humans.
• Less than 1 percent of the vanillin produced annually comes from vanilla beans. The remaining 99 percent comes from lignin or is produced by synthetic means.
• Small amounts of vanillin are present in the wood used to make wine casks and adds to the flavor of wine.
• The Coca-Cola Company is believed to be the world's largest buyer of pure vanillin. Since the company does not reveal the recipe for its products, that assumption cannot be confirmed.
• The word vanilla comes from the Spanish word vainilla, meaning "little sheath," which refers to the shape of the vanilla orchid.

Vanillin is considered safe for human consumption, although it can be toxic in very large quantities. Known reactions include respiratory irritation, including coughing and shortness of breath, and gastrointestinal tract irritation. Contact with the skin or eyes can also cause irritation, redness, and pain. These symptoms are virtually unknown except for individuals who work directly with the pure compounds.

FOR FURTHER INFORMATION

"All about Vanilla Extracts and Flavors." The Vanilla.COMpany. http://www.vanilla.com/html/facts-extracts.html (accessed on November 19, 2005).

"Aroma Chemicals from Petrochemical Feedstocks." National Economic and Development Council of South Africa. http://www.nedlac.org.za/research/fridge/aroma/part3/benchmarking.pdf (accessed on November 19, 2005).

"Food Guide Question." Gloucester Muslim Welfare Association. http://www.gmwa.org.uk/foodguide2/viewquestion.php?foodqid=69&catID=1&compID=1 (accessed on November 19, 2005).

Rain, Patricia. Vanilla: A Cultural History of the World's Most Popular Flavor and Fragrance. Edited by Jeremy P. Tarcher. New York: Penguin Group USA, 2004.

"Vanillin." Greener Industry. http://www.uyseg.org/greener_industry/pages/vanillin/1Vanillin_AP.htm (accessed on November 19, 2005).