Why Some Like It Hot: The Science of Spicy

Spicy, or the perception of it, is found in most cuisines around the world. The hot red pepper of the genus Capsicum (family Solanaceae) is one of the most widely used spices in the world, found in thousands of recipes and sometimes eaten as a separate dish. One in four people on the planet currently eat chili peppers every day.

As a forest ecophysiologist, I study the adaptive traits developed by plant organisms to interact with other living things and the environment.

The study of hot peppers and spiciness represents an outstanding example of multidisciplinary science. Several researchers in recent decades have provided information and curiosity about this most unique and desirable oral sensation.

Short story

Chili peppers were unknown to much of the world until Christopher Columbus made his way to the New World in 1492. Several origin theories point to different parts of South America as where chili peppers came from.

A phylogenetic analysis found them to be native to a region along the Andes from west to northwestern South America. These ancestral wild peppers were small red, round fruits similar to strawberries.

The earliest evidence of domestication dates back to 6,000 years ago in Mexico or northern Central America. Hot peppers were introduced to Europe in the 16th century. There are currently five domesticated species of chili peppers.

The five domesticated species are Capsicum annuum, C. chinense, C. frutescens, C. baccatum and C. pubescens. The species with the most varieties is C. annuum, which includes the New Mexican jalapeƱo and bell pepper. Habaneros and scotch bonnets instead belong to C. chinense, while Tabasco peppers are C. frutescens. South American ajis are C. baccatum, while Peruvian roccotos and Mexican manzanos are C. pubescens.

Nowadays, more than three million tons of chili peppers are produced annually for a global market that exceeds US$4 billion.

Why does chili burn?

Spicy is a burning sensation caused by capsaicin in food. When we eat spicy food, capsaicin stimulates receptors in our mouth called TRPV1 receptors and causes a reaction. The purpose of TRPV1 receptors is thermoreception, heat detection. This means that they should deter us from consuming food that burns.

When TRPV1 receptors are activated by capsaicin, the sensation we experience is related to the sensation of encountering something hot, close to the boiling point of water. However, this pain is nothing more than an illusory side effect of our confused neural receptors, there is nothing hot about spicy food.

Not all chili peppers are created equal

There are different degrees of spiciness depending on the chili you eat. In 1912, pharmacist Wilbur Scoville created a scale to measure the hotness (spiciness) of hot peppers. This scale, measured in Scoville heat units (SHU), is based on the sensitivity to capsaicinoids experienced by people who eat chili peppers.

On the standard Scoville heat scale, peppers (SHU=0) are at the bottom. Jalapeno peppers can range from 2,500 to 10,000. In comparison, Tabasco peppers are between 25,000 and 50,000 units, and habanero peppers range between 100,000 and 350,000.

The hottest pepper in the world, the Carolina Reaper, goes as high as 2.2 million units. Bear spray with two percent capsaicin is advertised at 3.3 million units, and pure capsaicin hits 16 million at the top of the Scoville scale.

Human pleasure

Psychologist Paul Bloom writes: Philosophers have often sought the defining characteristic of human language, rationality, culture, and so on. I’d stick with this: Man is the only animal that likes Tabasco sauce.

Bloom was right. There isn’t a single animal that loves chili peppers, but we’re not the only animal species that eats chili peppers. Mammals, such as mice and squirrels, share the same pungent food receptors as humans and tend to avoid hot peppers as a food source.

Birds eat chili peppers, but they don’t actually feel the heat. Birds have different receptors than humans and biologically cannot register the effects of capsaicin.

Explaining the reason for the evolution of capsaicin is not so easy. Some argue that this is an adaptation to select birds to eat chili fruits. Birds do not chew and grind seeds like rodents and carry them far away.

Other studies suggest that capsaicin is also an effective deterrent against the attack of parasitic fungi, and the sensation of warmth in mammals is a side effect.

Some experts claim that people like chili peppers because they are good for us. They have some beneficial effects on human health. They lower blood pressure and may have some antimicrobial effects. The pain from hot peppers can even beat and help manage other pains.

Another hypothesis can be described as benign masochism. Psychologist Paul Rosin suggests that there is a kind of thrill akin to the fun of riding a roller coaster. In an interview he explained: Mind over body. My body thinks I’m in trouble, but I know I’m not.

Reducing burnout

What happens when food is too hot to handle? Several common beverages have been tested for their ability to extinguish fire or reduce oral burn from capsaicin.

With capsaicin, a glass of water will be ineffective because capsaicin is hydrophobic, the molecule does not bind to water. Although it remains to be fully proven, the ethanol in cold beer may even increase the burning sensation.

Drinks with a significant amount of sugar can help because the activation of the taste for sweetness basically confuses our brain. Too many coping stimuli will reduce the hotness of the chilies.

A glass of milk, a few spoonfuls of yogurt or ice cream will soothe the burning sensation. These products are usually sweet, but there’s more: casein, the main protein in cow’s milk, attracts capsaicin molecules. The casein molecules surround the capsaicin molecules and wash them away, the same way soap washes away fat.

So the next time you want to try a new hot sauce or spicy dish, don’t forget to order a glass of milk.

(The talk: by Roberto Silvestro, PhD candidate in biology, Universite du Quebec a Chicoutimi)

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