Chemistry of YUM!
By Lydia from SLN
From the Science Bits in a World of Bytes Blog Series
It is so satisfying to cook and bake because the results delight the eye, nose, and mouth. I’ve thrown broccoli slaw, onions, and zucchini into a pan, added spices and pasta sauce and made myself a tasty, if unusual, meal. Not all of my cooking is so healthy; I enjoy brownies, cookies, and pies as much as the next person. Regardless of nutritional content, all of my favorite foods have ingredients with certain chemicals that make my mouth water.
I use onion in a lot of my savory cooking because it adds so much flavor. I’m not alone; my mom was working a fundraiser, and she was cooking some food. She dumped some onions on the griddle, and the smell reeled in people. Someone was waxing so poetic about the carmelized onions that she thought he would have a bun with just onions on it.
Certain chemicals give onions their flavor; most involve the element sulfur in the form of thiosulfinates, which contain sulfur with a single bond to another sulfur and a double bond with an oxygen atom. Different molecules are distinguished by the groups attached to the sulfur atoms.
The compound that makes you cry is a smaller structure:
Onions and garlic go together like macaroni and cheese. (Actually, they’d probably go well in mac and cheese.) Garlic and onions are in the same family and so are flavored by the same class of compounds, thiosulfinates.
The main component of garlic flavor is allicin. The plant uses this molecule to ward off pests. Sorry, garlic; you can’t win. What makes you resistable to insects makes you irresistible to us.
Allicin is unstable and degrades into beneficial breakdown products that do much to enhance health, such as protecting the heart and preventing cancer.
Black pepper has been one of the most popular spices in history. It is, in fact, called “The King of Spices.” Piperine gives pepper its kick. The receptor named TPV1 senses it; this particular receptor is also involved in the sensing of pain. Considering the burning sensation that ingesting too much pepper gives, this makes sense.
Piperine is under investigation for its ability to alter the metabolism of pharmaceuticals, making them available for longer times in the body. Companies have put it to a more sinister use as an ingredient in pesticides, which I suppose is why it’s in the plant in the first place. It works on contact. In the cowpea beetle, it reduces the number of eggs laid by the female and the emergence of adults. In another type of beetle, the bruchid, it is thought that it irritates the cuticle, possibly causing loss of bodily fluids. It also blocks the spiracles, the holes which allow the beetle to breathe. To crown it all, piperine can kill nerve cells in large enough doses.
Another chemical to set your mouth on fire is capsaicin. It, too, is sensed by TPV1. It is commonly found in hot peppers, again used as a deterrent against things that would eat the plant.
We people are a weird species. Besides cooking, capsaicin has found use in self-defense sprays and topical pain relievers. These, however, are not without risk. People have reported respiratory problems, especially in asthmatics, and irritation of the skin.
To soothe a cough or sore throat, my mom prescribes a mug of lemon-honey-ginger tea. It’s full of good things. The citric acid in the lemons has bacteriocidal properties due to its low pH, and the lemon smell improves the mood, which really helps when you’re sick. The honey acts as a sweetener and can also help inhibit bacterial activity. This property stems from the makeup of honey. It has water content ranging from 15 to 19 percent and sugars at about three-quarters. This dry environment makes bacterial growth impossible. The beneficial aspects of ginger can be attributed to three molecules: zingerone, shogaol, and gingerol. Only shogaol and gingerol are found in fresh ginger. Zingerone is produced upon cooking, which lops off part of the long chain present in gingerol. This has been shown to have antidiarrheal properties. Shogaol is produced in the dehydration of gingerol and has been investigated for pharmaceutical activity.
Gingerol is the main component of fresh ginger’s flavor. Of the three, it is the one that most closely resembles its chemical cousins piperine and capsaicin. It shows a promising range of benefits, including reducing nausea and treating cancer.
The food we eat is a conglomeration of chemicals, and I’ve shown only a few of the molecules that add up to tastiness. Structure determines function, so the ones like zingerone, gingerol, and piperine give off similar taste sensations. Many of these molecules have health benefits in addition to their killer flavors, so eat up!
Amagase, Harunobu, Brenda Petesch, et al. "Intake of Garlic and Its Bioactive Components." Journal of Nutrition. 131.3 (2001): 9555-9625. Web. 14 Feb. 2013.
Bhardwaj, Rajinder, Hartmut Glaeser, et al. "Piperine, a Major Constituent of Black Pepper Inhibits Human P-glycoprotein and CYP3A4." Journal of Pharmacology and Experimental Therapeutics. 302.2 (2002): 645-650. Web. 27 Feb. 2013.
Idoko, J.E., and J.M. Adesina. "Evaluation of the Powder of Piper Guineense and Primophos-Methyl F for the Control of the cowpea Beetle Callosobruchus Maculatus." Journal of Agricultural Techonology. 8.4 (2012): 1365-1374. Web.
Lanzotti, Virginia. "The Analysis of Onion and Garlic." Journal of Chromatography. (2006): 3-22. Web. 14 Feb. 2013.
McNamara, Fergal, Andrew Randall, and Martin Gunthorpe. "Effects of piperine, the pungent component of black pepper, at the human vanilloid receptor (TRPV1)." British Journal of Pharmacology. 144.6 (2005): 781-790. Web. 14 Feb. 2013.
Reilly, Christopher, Dennis Crouch, et al. "Determination of Capsaicin, Nonivamide, and Dihydrocapsaicin in Blood and Tissue by Liquid Chromatography-Tandem Mass Spectrometry." Journal of Analytical Toxicology. 26. (2002): 313-319. Web. 14 Feb. 2013.
Szallasi, Arpad. "Piperine: Researchers discover New Flavor in Ancient Spice." TRENDS in Pharmacological Sciences. 26.9 (2005): 437-439. Web. 14 Feb. 2013.
Unchern, Surachai, Hiroshi Saito, and Nobuyoshi Nishiyama. "Selective Cytotoxicity of Piperin on Cultured rat Hippocampal Neurons in Comparison with Cultured Astrocytes: The Possible Involvement of Lipid Peroxidation." Biological Pharmeceutical Bulletin. 20.9 (1997): 958-961. Web. 20 Feb. 2013.