Gardening for You. Capsaicin in chile gives the heat
Today’s column looks at chile heat chemistry. But first, how to classify chile. When eaten, chile is a vegetable, a fruit in horticulture but it can also be a spice. Pigments found in chile are used as food coloring, unique chemical constituents have medicinal and analgesic properties and extracts can be used as sprays for personal defense.
The fruit of a chile plant is horticulturally and correctly called a pod. When chile is consumed as main ingredient or added to dips and specialty dishes, it is a vegetable but when dehydrated and ground chile is becomes a spice.
The specific epithet of chile is Capsicum annuum. The genus Capsicum is derived from the Greek “kaptos”, which means “to bite”. The compound in chile that gives pods pungency, medicinal and defense properties is the molecule capsaicin (cap-SIGH-a-sin).
Capsaicin is the chemical synthesized in chiles and peppers that is responsible for its heat. Capsaicin is not found throughout the pod but is located in specialized glands in the interior of the pod.
Slicing a pod in half lengthwise exposes the interior of the pod, revealing the glands.
Chile pods have thick walls with tough outer skins called the exocarp (exo, external). Chiles are roasted to blister the skin, making the tough exocarp easier to peel off. The thick outer walls of mature pods are composed of the tissues called pericarp (peri, around), found just under the exocarp, and further inside is the fleshy mesocarp (meso, middle). Connected to the mesocarp are capsaicin glands that are found along the innermost interior placental membrane, the specialized membrane to which the seeds are attached.
Capsaicin molecules are synthesized in the placenta. The heat of capsaicin molecules is contained in the placental membrane that holds the seeds, but not the seeds themselves.
The amount of capsaicin inside a pepper is quantified by the Scoville Scale, expressed in Scoville Heat Units (SHU). SHU are comparative values because heat levels can fluctuate by location, even in pods on the same plant. SHU range from 0 (bell peppers) to 3,000,000 in Pepper X, the spiciest chile in the world (Chile Pepper Institute NMSU). The chiles in the photo are likely mild 'New Mexico 6-4’ with SHU of about 1,500.
The burning sensation upon ingesting capsaicin is due to receptors on the tongue that stimulate chemical responses in the body. Numbers of receptors vary with individuals, leaving some with greater heat tolerance than other individuals.
Chemistry answers the desire to drink after eating capsaicin. Capsaicin molecules are nonpolar, therefore, follow only with non-polar substances. Drinking water exacerbates the heat sensation. Water cannot dissolve capsaicin and actually spreads heat all over the mouth because water is a polar molecule, but casein proteins found in milk dissolve capsaicin. To relieve the burning sensation of capsaicin, drink milk or eat ice cream.
Ellen Peffley taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at gardens@suddenlink.net
This article originally appeared on Lubbock Avalanche-Journal: Gardening for You. Capsaicin in chile gives the heat
