Properties of vanillin

Vanillin, perhaps the most important aroma compound, occurs in the bean of Vanilla planifolia. At present in the world flavor market, only 0.2% of this compound is extracted from beans; the remainder is produced synthetically.

Vanilla planifolia

Vanillin is a colorless, crystalline solid (melting point 82-83 ° C) with a typical vanilla odor.

Because it posses aldehyde and hydroxy substituents, it undergoes many reactions. Additional reactions are possible due to the reactivity due the aromatic nucleus. Since vanillin is a phenol aldehyde, it is stable to autooxidation and does not undergo the Cannizzaro reaction.

In common with many other low-molecular weight phenolic compounds, vanillin displays antioxidant and antimicrobial properties and hence has the potential for use as food preservative.

It is active against both Gram-positive and Gran-negative food spoilage bacteria and has been shown to be effective against both yeasts and moulds in fruit purees and laboratory growth media.

Vanillin exhibits in vitro antifungal activity against the yeasts Candida albicans and Cryptoccoccus neoformans. Minimal inhibitory concentrations of vanillin for C. albicans and C. neoformans were found to be 1250 and 738 ug/ml.

Vanillin is found to be a good antioxidant. It offers significantly good protection against protein oxidation and lipid peroxidation induced by photosensitization in rat liver mitochondria.
Properties of vanillin

Theory of odor

The sense of smell is important to human beings and has always been so. The human nose has an almost unbelievable ability to distinguish odors.

The lock and key theory of odor (systemic effect theory) suggest that odor acts very much like a specific neurotransmitter, a drug or an enzyme.  In this paradigm, an odorant has a specific effect on behavior or emotion – one odor for one emotion or one odor for at most a few emotions.

The stereochemical theory of odor suggests that a molecule that fits into an olfactory receptor can fire nerve cells, ultimately producing a particular odor perception.

Lucretius, one of the early Greek atomists, suggested that substances having odor gave off a vapor of tiny ‘atoms’, all the same shape and size, and that these atoms gave rise to the perception of odor when they entered pores on the nose.

Five basic odors were associated with different molecular shapes. Football shaped molecules fit in to a "camphoraceous" receptor, and smell like mothballs.  Necklace-shaped molecules have a musky odor because they fit into a "musky" receptor.

While, wedged-shaped molecules have a pepperminty odor, tadpole-shaped molecules smell like flowers, and long thin ether molecules are, well, ethereal.

A substance must have certain physical characteristics to have the property of odor:
*It must be volatile enough to give off vapor that can reach nostrils
*It must be water soluble, so that it can pass the layer of moisture (mucus)
*It must have lipid solubility to allow it to penetrate the lipid layers that form the surface membranes
Theory of odor

Garlic

Garlic
Botanically name Allium sativum, L. Because of their attractive flavor and acknowledged medicinal properties the bulb or “cloves” of garlic have been used in the cuisine of most Mediterranean countries since the dawn of history.

Like onions the entire cloves are almost without odor but once cut or bruised they produce an intensity strong and characteristics odor which too many is obnoxious.

The chemistry of the compounds responsible for the garlic profile is similar to the found in onion. The differences are attributed to qualitative and quantitative differences in the precursors present; the active ingredients being primarily allyl (2-propenyl) sulfides together with much smaller amounts of methyl and 1-prophykl compounds.

The flavor of onion and garlic is complementary the former being mild and sweet whereas the latter is harsh and insistent, because of its relatively high flavoring power, garlic is frequently blended with onion in order to increase the initial impact of the onion but this can only be done to a very limited extent as garlic is quickly recognizable as such and its flavor associations are not always acceptable.

If garlic is incorporated into an end product which is to be distributed in a container such as a screw capped bottle or jar, the head space above the product nearly always has a higher proportion of the garlic odor.

This may be detectable as such and detract from the product even though the product itself may not contain a sufficient level of garlic to be noticeable when the product is consumed.
Garlic

Cornmint Oil

Cornmint Oil
Botanically name Mentha Arvensis. About 7,100 tons of cornmint oil (sometimes incorrectly called Chinese peppermint oil) are produced annually.

It is almost all converted into menthol (2,800 tons) and dementholized oil (4,300 tons). China accounts for around 65% of the world production and India accounts for most of the remainder.

Dried plants yield 2.5% oil by steam distillation. Cheap synthetic menthol has reduced the demand for cornmint oil into the main markets in the Unites States, Western Europe and Japan.

The major quantitative components of the dementholized oil are typically:
35% laevo- menthol (cooling, light, mint)
30% laevo-menthone (harsh, herbal, mint)
8% iso-menthone (harsh, herbal, mint)
5%limonene (weak light, citrus)
3% laevo-menthyl acetate (light, cedar, mint)
3% piperitone (herbal, mint)
1% octa-3-ol (herbal, oily)

Cornmint oil contains about 1% of pulegone (pennyroyal mint odor) which is suspected of being toxic. The raw oils are rectified to remove some of the front and back fractions.

Careful blending of fractions can reduce the characteristically harsh odor of cornmint oil but it still remains much less attractive than peppermint oil. Adulteration of cornmint oil is not a commercially attractive proposition.

Most cornmint oils are used to give a cheap peppermint flavor to a wide range of applications often blended with true peppermint oil. It is more frequently used in blended flavors than peppermint oil because of its price advantage.
Cornmint Oil

Cassia oil

Cassia oil
It’s extracted from plant Cinnamonum cassia. Virtually all of the more than 500 tons of cassia oil produced annually originate in China. Very small quantities are produced in Taiwan, Indonesia and Vietnam. Leaves, twigs, and sometimes inferior bark 0.3% oil by water distillation. Demand is increasing steadily despite unpredictable production levels in China.

The major quantitative components of the oil are typically:

• 85% cinnamaldehyde (spicy warm, cinnamon)
• 11% o-methoxy cinnamaldehyde (musty, spicy)
• 6% cinnamyl acetate (sweet, balsamic)

Other qualitatively important components are:

• 1% benzaldehyde (bitter almond)
• 0.4% ethyl cinnamate (balsamic, fruity)
• 0.2% salicylaldehyde (pungent, phenolics)
• 0.2% coumarin (sweet, hay)

Coumarin is suspected of being toxic. Cinnamaldehyde is the most important contributor to the characteristic odor of cassia but o-methoxy cinnamaldehyde is mainly responsible for the unique note which distinguishes cassia from cinnamon oil. Cassia oil is often imported in a crude state and required redistillation to improve the odor and remove metallic impurities. Adulteration of the oil with cinnamaldehyde is practiced but can be easily detected by gas chromatography.

In the flavor industry, the oil makes a unique contribution. In its own right, it is a major part of the traditional; flavor of cola drinks. It is used in confectionary, sometimes in conjunction with capsicum oleoresin. Use of cassia oil in other natural flavors is restricted to cherry, vanilla and some nuts flavors. There are no legal constraints in the use of cassia oil in flavors.
Cassia oil

Molecular fundamental of food flavor

A similar lock-and-key type of model has been used to explain why different substances have different flavors. The stereochemical theory of odor suggests that a molecule that fits into an olfactory receptor can fire nerve cells, ultimately producing a particular odor perception.

Five basic odors were associated with different molecular shapes. Football shaped molecules fit in to a "camphoraceous" receptor, and smell like mothballs. Necklace-shaped molecules have a musky odor because they fit into a "musky" receptor. Wedged-shaped molecules have a pepperminty odor, tadpole-shaped molecules smell like flowers, and long thin ether molecules are, well, ethereal.

Putrid and pungent smells were explained on the basis of partial charges on atoms within the molecule, rather than by shape alone. Putrid molecules have a buildup of negative charge somewhere in the molecule that's strongly attracted to a partially positive site on the "putrid" receptor. Pungent molecules (like acetic acid, in vinegar) are just the opposite: they have an electron-deficient region that is strongly attracted to an electron-rich site on the "pungent" receptor.

These seven receptors were believed to be the only letters in the olfactory alphabet in Amoore's version of the theory, published in the early 1970's. Molecules that can lock into more than one receptor have more complex odors. For example, Amoore explained the almondy odor of benzaldehyde by showing that it could fit comfortably into the postulated shapes for the camphoraceous, floral, and pepperminty receptors.

Amoore's stereochemical theory is now known to be an oversimplification, but it's still useful in relating smells to molecular shapes. There are over a thousand olfactory receptors, not just seven. The molecule's ability to move through tissue containing layer after layer of receptors also determines how its odor is perceived.

For example, attaching a hydrocarbon tail to a molecule improves its solubility in fats and alters its behavior at cell membranes. Perfume chemists have long known that adding a hydrocarbon tail to some perfume molecules increases their potency. Next article we will look to some specific examples.
Molecular fundamental of food flavor