Capsaicin: active component of chili pepper

Capsaicin is the spicy, pungent compound of chili peppers, and the most fiery of the pepper alkaloids. Capsaicin probably evolved to protect the pepper from being eaten by predators.

Capsaicin, also known as N-Vanillyl-8-methyl-6-(E)- noneamide, is the most pungent of the group of compounds called capsaicinoids.

The biosyntheses of capsaicinoids takes place in the fruit and they are stored mainly in the placenta (the central portion in the fruit to which the seeds are attached). Capsaicin is an alkaloid. Chemically, capsaicin is trans-8-methyl-Nvanillyl-6-nonenamide.

Capsaicin

Capsaicin has a molecular weight of 305.40 and forms white translucent crystals that melt at 64.5°C.

In humans, this substance can help digestion by stimulating salivation, stomach acid production, and, perhaps, peristalsis. Capsaicin has other potential benefits: It may also kill bacteria, reduce the risk of blood clots, and serve as an antioxidant.
Capsaicin: active component of chili pepper

Shogaols compound in ginger

Gingerols and shogaols are the chemesthetic compounds found in species from the Zingiber genus, ginger being the most common species. Shogaols, a monodehydrated gingerol was reported to be a pungent component of ginger.

Gingerols, through dehydration, form shogoals. Zingerone, a compound not found in fresh ginger, is formed by a retro-aldol reaction when gingerol is heated.

Usually, the fresh rhizome contains none or very small amounts of shogaols, while the dried rhizome is rich in shogaols. This suggests that shogaols are formed through dehydration during processing or storage of the fresh rhizome.

With formation of shogaols by the dehydration of gingerol, the pungency doubles - which is why aged ginger usually has a stronger bite.

HPLC is by far the most popular technique to separate and detect gingerols and shogaols in ginger.
Shogaols compound in ginger

Black and White Pepper

Black and White Pepper
The pepper of commerce is produced from unripe fruits of the perennial climbing vine and is available in two distinct forms – black pepper and white pepper.

The former consists of the whole dried fruits picked while still green and sun dried.

During drying they turn to a brownish black color with the individual peppercorns having a much wrinkled outer skin.

White pepper is the dried kernel of the fruits which are gathered when they are just turning slightly yellow.

The fruit are subsequently soaked in water to soften and loosen the outer skin which is then removed by friction, white peppercorns are smooth surfaced.

Pepper originated in the Western Ghats of India from where it has spread to many parts of tropical Asia, notably Indonesia, Cambodia, Vietnam and Sri Lanka.

As a seasoning and condiment, pepper is second to none, and its use is ubiquitous.

The distinctive odor and flavor of pepper overlie its pungency due to its essential oil content which varies both quantitatively and qualitatively between sources and varieties.

The chemical composition of the oil is complex and is present from 1 to 3%.

The oil from white pepper contains similar components to that from black pepper are markedly different from that of the spice stored in a ground condition as regular users of the domestic pepper mill will readily attest.

Not only does the ground material soon lose it pleasing freshness but it also develops an obvious and insistent ammoniacal note which detracts from its true peppery character.

The profile of essential oil distilled directly from freshly crushed peppercorns has a most attractive nuance much appreciated in blending of high quality, spicy fragrances.
Black and White Pepper

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