Preface: I had intended on finishing our series on taste sense with a single post on how spicy foods are a taste exception. But the information and exceptions kept pouring out of the literature; every turn gave me a new feature to look at in more depth. So, instead of a single post, here is the first in a series on spicy foods and how our sensation of spiciness or coolness is related to many biological concepts and functions. We experience these daily without ever thinking about them, but the exceptions will show just how inventive life can be.
Here is the fruit of the jalapeno pepper. It is formed from
a single ovary, where the pericarp (ovary wall) is made up
of the exocarp, mesocarp, and endocarp. The placenta is
also called the septum, and on the sides of it are the
Chili peppers are indeed considered fruits. They are true berries, but they are the exception in berries, as they don’t have a fleshy middle; they're mostly hollow. They form from a single ovary, and the chili is the entire ovary wall ripened into an edible form called a pericarp.
The capsaicin (the dominant spicy molecule in chili peppers) is present in all the fruit structures, but there are higher concentrations in the seeds and the ribs (septa) that hold the seeds to the inner face of the fruit wall. Even the hottest peppers have tastes other than spice, but it's really a matter of how much capsaicin is packed into the flesh that determines the overall sting of the pepper.
Chili peppers got the name "pepper" because they were spicy, like the black pepper plant, but there's no botanical relationship between these two kinds of plants. Chili peppers are from the genus Capsicum. There are about 27 species in the genus, but each species comes in several varieties – bell peppers and jalapenos come from the same species. The Capsicum genus is just one of the 90 or so genera in the family Solanacae, the nightshades. This is a diverse family of plants, including potatoes, tomatoes, tobacco, petunias, and even some trees.
But on the other hand, why put the hot stuff in the fruits? Don’t you want animals to eat the fruits and then spread the seeds around in their feces? Isn’t that the point of making a fruit – to entice some animal to disperse your seeds? It makes one wonder.
For what ever reason they do it, there's a new king of the spicy fruits: the Carolina Reaper. Bred in South Carolina specifically to be the world’s spiciest pepper, the Reaper weighs in at a whopping 1.6 million Scoville heat units. Here is a video of some nut downing one, but be careful – there's vomiting involved. That should give you some idea of this pepper’s powerful potency.
What’s a Scoville heat unit (SHU), you ask? In the test originally designed by pharmacist Wilbur Scoville in 1912, this number referred to the number of squirts of sugar water needed to extinguish the flames in your mouth after you bite a pepper. Later, SHU became more scientifically defined as the number of dilutions needed to make a given mass of chili flesh lose its sting. But this was still a subjective measure, with different people reporting different dilutions as necessary.
The 1.6 million SHU for the Carolina Reaper is about 100,000 units more than the previous record holder, the Trinidad Morgua Scorpion pepper, which is still the spiciest pepper that grows in the wild. Take note that the value is the average for a batch of the peppers grown at the same time at the same place, but the SHU will vary from pepper to pepper.
For the Reaper, at least one individual pepper has been measured at more than 2.2 million SHU, and a Morgua Scorpion individual has come close to this at 2.01 million SHU. The individual differences can come from slight variations in environmental and soil conditions between plants.
A 2013 study found that temperature will affect capsaicin levels. For several pepper cultivars, as the growing temperature increased, so did the capsaicin levels. But the effect was the opposite in jalapenos; higher growing temperatures led to lower capsaicin levels.
The cause of all this spiciness – capsaicin. It's not a protein, but is more aptly described as a nitrogen containing fatty acid – yet another amazing fat. It is one of many compounds called vanilloids, named after one member, the vanillin molecule that gives us vanilla taste and aroma.
The best bet to take the sting out of your curry is whole milk. Why? Because whole milk has sufficient fat to draw the capsaicin off your tongue, and milk also contains a protein called casein. Casein is lipophilic (lipo = fat, and philic = loving), so it will take the capsaicin off your tongue too. You won’t look very manly, but at least you’ll survive.
Many “professional” chili eaters don’t worry about the manly thing at all. After proving how strong they are by eating a ghost pepper or a Carolina Reaper, they will often fill their mouth with Cheez Whiz, or even shove cheesecake up their nose to try and placate their burning nasal membranes!
Pure capsaicin is rated at 16 million SHU, so even the hottest Carolina Reaper is only 1/8 as spicy as theoretically possible. Of course there is no way you could make a pepper that contains only capsaicin. The chili with the best public relations firm is the Ghost Pepper (Bhut Jolokia) of India. The Ghost is all the rage in culinary spice these days, but it only carries a 1 million SHU warning. I wonder if your mouth can actually feel (not taste) the difference between a Carolina Reaper, a Morgua Scorpion and a Ghost Pepper. I’m not planning to investigate my question.
Habaneros range from 350,000 to 500,000 SHU, depending on the cultivar (Red Savina habaneros were developed to be hotter). Jalapenos manage only a 3500-8000 on Scoville’s scale, and I have a hard time with these!
Now for a question with a seemingly easy answer, but one that opens many doors for investigation. Why do we say that spicy foods are “hot?” In culinary terms, “hotness” is made distinct from other spice characteristics by being called piquancy. Chili peppers are piquant (from Middle French for irritating or pricking), not hot. This is where we get the name of picante sauce.
The capsaicin in chili peppers causes pain in the mouth, like a burning sensation. It burns on the skin as well. And eating peppers make you sweat, just like when it is very hot. I'm guessing that this is where the term "hot food" came from. With very spicy peppers, like the reaper or the Morgua Scorpion, the amount of capsaicin brings blistering of the oral mucosa. Basically, your body is sensing a burn, and creates blisters to try and keep the burning compound away from the deeper tissue.
It's true that the closer to the equator people live, the more chili peppers they tend to eat. Believe it or not, eating peppers helps to cool you off. On a very hot day, the heat builds up in your body and you need to get rid of it. Sweating is one way we dissipate heat; the evaporation of water from the skin requires an input of energy, and this comes from the heat of the skin. The loss of heat makes you feel cooler.
So how does eating a pepper turn into a sensation of burning and pain? You definitely transmit neural signals of pain when you are burned by heat, and this is the key. The protein on pain neurons that sense burning heat and conduct the signal to the brain to be perceived as pain – well that same protein is activated by capsaicin! The signal is the same; your brain doesn’t know the difference between activation by capsaicin and activation by scalding heat – it interprets them both as pain!
The protein responsible for this is called TRPV1, and we will have much more to say about this ion channel in the weeks to come. It's a heat sensor, a pain sensor, an acid sensor. It can create pain and inhibit pain. It can cause itch and cough, and maybe prevent cancer. Oh, and it creates vampire bats too.
For more information or classroom activities, see:
Scoville heat scale –
Chili fruits –
Fusarium fungus –