Spiciness is not a flavor detected by taste buds, but rather a sensation of heat or irritation. This feeling is triggered by specific chemical compounds.
The Main Chemical: Capsaicin
The primary chemical responsible for the heat in chili peppers is capsaicin. It is a colorless, odorless, crystalline alkaloid. Capsaicin originates in plants of the Capsicum genus, which includes all chili peppers.
This compound is produced in the placenta of the pepper, the white pith where the seeds are attached, and to a lesser extent, in other fleshy parts of the fruit. Capsaicin plays an evolutionary role for the chili plant, acting as a deterrent against mammals that might consume the fruit and destroy the seeds. Birds, however, are unaffected by capsaicin, allowing them to disperse the seeds effectively.
How Your Body Detects Spiciness
The sensation of spiciness arises when capsaicin interacts with specific receptors on nerve endings. These sensory receptors, primarily the Transient Receptor Potential Vanilloid 1 (TRPV1) receptor, are found in the mouth, skin, and mucous membranes. The TRPV1 receptor is a non-selective cation channel, meaning it allows various positively charged ions to pass through it.
When capsaicin binds to the TRPV1 receptor, it causes the ion channel to open. This opening allows calcium ions to rush into the nerve cell. The influx of calcium ions generates an electrical signal that the brain interprets as a burning or painful sensation, similar to the feeling of actual heat. This mechanism explains why spicy foods can feel hot, even though no actual temperature change occurs.
Measuring the Heat: The Scoville Scale
The heat level of chili peppers is quantified using the Scoville Scale, developed by American pharmacist Wilbur Scoville in 1912. A Scoville Heat Unit (SHU) represents the degree of dilution required for a solution of pepper extract to no longer be detectable as spicy by a panel of tasters.
For instance, if an extract needs to be diluted 1,000 times, it registers as 1,000 SHU. While the original Scoville Organoleptic Test relied on human subjectivity, modern methods use High-Performance Liquid Chromatography (HPLC) for more precise measurement. HPLC quantifies the concentration of capsaicinoids, which is then converted to SHU.
Bell peppers, lacking capsaicin, have 0 SHU. Jalapeños typically range from 2,000 to 8,000 SHU, while habaneros can reach 100,000 to 350,000 SHU. The Carolina Reaper, one of the world’s hottest peppers, can exceed 2 million SHU.
Other Compounds That Create Heat
While capsaicin is prominent in chili peppers, other compounds also produce a spicy sensation. Piperine, found in black pepper, contributes to its distinct pungency. Gingerol, present in ginger, is responsible for its characteristic spicy and pungent flavor.
Isothiocyanates are volatile compounds found in mustard, horseradish, and wasabi. These chemicals create a sharp, often nasal and sinus, burning sensation. Unlike capsaicin, isothiocyanates primarily activate the TRPA1 receptors, contributing to a different sensory experience.
Soothing the Spicy Sensation
Alleviating the burning sensation from spicy foods often requires methods beyond simply drinking water. Water is ineffective because capsaicin is oil-soluble and hydrophobic, meaning it does not mix with water and can instead spread the sensation around.
Dairy products, such as milk or yogurt, are effective remedies because they contain casein protein. Casein binds to capsaicin molecules, helping to wash them away from the pain receptors.
Sugar or honey can also help by diluting the capsaicin or by overwhelming the taste buds with sweetness. Alcohol, being a solvent, can dissolve capsaicin due to its lipophilic nature. Additionally, starchy foods like bread or rice can provide some relief by physically absorbing a portion of the capsaicin.