Pungency describes a distinct sensation often felt as sharpness, stinging, or heat in the mouth. This experience arises from chemical irritants interacting with our sensory system, rather than being one of the five basic tastes like sweet, sour, salty, bitter, or umami.
The Chemistry of Pungency
Specific chemical compounds are responsible for generating the sensation of pungency in various foods. Capsaicinoids, particularly capsaicin, are the active components in chili peppers, causing their characteristic heat. These compounds are alkaloids, nitrogen-containing substances, and are primarily found coating the seeds of chili pepper fruits. Plants often produce these compounds as a defense mechanism against herbivores and pathogens, such as fungi.
Piperine is another pungent compound, widely recognized as the substance that gives black pepper its bite. Allyl isothiocyanate, commonly found in mustard, horseradish, and wasabi, also contributes to a sharp, irritating sensation.
Allicin is the primary pungent compound in raw garlic and onions. It is formed when the plant’s cells are damaged, such as by crushing, through a reaction catalyzed by the enzyme alliinase.
How We Perceive Pungency
The human body perceives pungency not through taste buds, but through specialized pain and temperature receptors located on nerve endings. These nerve endings are part of the somatosensory system, which detects various stimuli including pressure, temperature, and chemical irritants in areas like the oral and nasal cavities. The trigeminal nerve, a major sensory pathway, transmits these signals from the face, nose, and mouth to the brain.
Specific transient receptor potential (TRP) channels play a significant role in detecting these pungent chemicals. The TRPV1 receptor is activated by capsaicin, the compound in chili peppers, and also by temperatures above approximately 43°C, leading to the sensation of heat. This receptor is highly expressed in sensory neurons, including those of the trigeminal nerve.
Another important receptor is TRPA1, which responds to compounds like allyl isothiocyanate from mustard and wasabi, and allicin from garlic. Activation of these TRP channels on sensory neurons sends signals to the brain, which are interpreted as the burning or stinging feeling associated with pungent foods. This neurological response explains why these substances can feel painful or hot, even though they do not involve actual temperature changes.
Measuring Pungency
The Scoville scale is a widely recognized method for quantifying the pungency of chili peppers and other substances. Pharmacist Wilbur Scoville developed the original method in 1912, known as the Scoville Organoleptic Test. This test involved dissolving dried pepper extract in alcohol and then diluting it with sugar water until a panel of five trained tasters could no longer detect any heat. The number of dilutions required was then assigned as the Scoville Heat Units (SHU).
Since the 1980s, a more objective and accurate method, High-Performance Liquid Chromatography (HPLC), has largely replaced the original subjective test. HPLC measures the concentration of capsaicinoids, the heat-producing chemicals, directly. The results from HPLC are converted to Scoville Heat Units by multiplying the parts-per-million of capsaicinoids by a conversion factor, typically 16.
On this scale, a bell pepper has 0 SHU, indicating no detectable pungency. A jalapeño pepper typically ranges from 2,500 to 8,000 SHU, while a habanero pepper can reach between 100,000 and 350,000 SHU. Extremely hot varieties, like the ghost pepper, can exceed 1 million SHU.