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.
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.
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.
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.
