Chemical Properties of Spices

Science questions not covered in Chem 14A and 14B. Try to limit questions to chemistry (inorganic chemistry, physical chemistry, organic chemistry, biophysical chemistry, biochemistry, materials science, environmental chemistry).

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Alex Uy 2D
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Chemical Properties of Spices

Postby Alex Uy 2D » Fri Oct 07, 2016 2:19 pm

What makes something spicy? For example, in a pepper what is the actual physical/chemical property that makes us experience "spiciness"? Is it a specific molecule or does it depend on the structure?

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Re: Chemical Properties of Spices

Postby Chem_Mod » Mon Oct 10, 2016 12:07 am

Both. Specific molecules in the pepper have the correct chemical structure to bind receptors that result in nerve stimulation we call spicy.

For example.
Capsaicin, the principle ingredient responsible for the pungency of hot peppers, is eaten daily by over a third of the world's population. Capsaicin activates responses in a subset of nociceptive C fibers by opening ligand-gated ion channels that permit the entry of Na+ and Ca2+.

One of these channels (VR-1) has been cloned and has been found to be activated by capsaicin, acid, and anandamide (an endogeneous compound that also activates cannabanoid receptors), and by heating the tissue to about 43°C. It follows that anandamide and temperature are probably the endogenous activators of these channels. Mice whose VR-1 receptors have been knocked out drink capsaicin solutions as if they were water. Receptors for capsaicin have been found in polymodal nociceptors of all mammals, but are not present in birds (leading to the production of squirrel-proof birdseed laced with capsaicin!).

When applied to the mucus membranes of the oral cavity, capsaicin acts as an irritant, producing protective reactions. When injected into skin, it produces a burning pain and elicits hyperalgesia to thermal and mechanical stimuli. Repeated applications of capsaicin also desensitize pain fibers and prevent neuromodulators such as substance P, VIP, and somatostatin from being released by peripheral and central nerve terminals.

Consequently, capsaicin is used clinically as an analgesic and anti-inflammatory agent; it is usually applied topically in a cream (0.075%) to relieve the pain associated with arthritis, postherpetic neuralgia, mastectomy, and trigeminal neuralgia. Thus, this remarkable chemical irritant not only gives gustatory pleasure on an enormous scale, but is also a useful pain reliever!


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