The potent spicy heat you experience eating chili peppers is caused by capsaicin, a colorless, odorless, waxy compound found in the white pith of the pepper’s inner wall where the seeds are attached.
Capsaicin is an irritant to most mammals—including humans; the sensation it leaves when it comes in contact with mucus membranes of most herbivores is one of burning—thus we commonly classify chili peppers by their heat or bite. The more capsaicin in a chili—actually measured chemically in parts per million—the hotter the pepper.
Measuring Pepper Heat: Scoville Scale
The measure for capsaicin pungency in peppers is called the Scoville scale, named for American pharmacist Wilbur Scoville who developed the scale in 1912. The greater the number of units on the Scoville scale the hotter the pepper. A sweet bell pepper has 0 Scoville heat units (SHUs); the Naga Viper pepper, one of the world’s hottest peppers, has 1,382,118 SHU; by comparison, a jalapeño pepper—hot enough to cause most humans some discomfort–has 2,500 to 8,000 SHU.
The shape and size of chili peppers was once a sure indicator of a pepper’s heat; tiny and small and long and thin peppers would be hot, but pepper breeders have changed all that—today you can find jalapeños and other chiles that have been bred to be mild.
Choosing a Hot Pepper
The best way to know how hot a pepper is: read the grower’s description, the plant label, or seed packet and look for these descriptors–mild, hot, or very hot. And, of course, tasting is a sure way to understand a pepper’s heat, but it is best to err on the side of caution if you are unsure of a pepper’s pungency—begin with small amount and increase the amount as you get used to it. (The antidote to pepper burn on the tongue: bananas, milk, yogurt, and granulated sugar are often mentioned by pepper lovers.)
Care in Using Hot Peppers
Because capsaicin resides in the white pith surrounding the seeds in the pepper’s inner wall, you can trim and wash the pith away to dilute the capsaicin, but use disposable kitchen gloves and avoid wiping your eyes or nose or other moist mucus membranes. Wash your hands with vinegar or soap when you are finished working with hot peppers. (The good news when it comes to eating hot peppers—besides the enjoyment you get from spicy food—is that capsaicin can improve digestion by increasing digestive fluids in the stomach and by fighting bacteria that can cause stomach infections.)
Heat Range of Peppers Commonly Grown in Home Vegetable Gardens:
(OP=open-pollinated, which means you can save the seeds and plant them again next season; and growing days to maturity from transplanting into the garden)
- Bhut Jolokia (also called Ghost Pepper): 1,001,304 SHU (OP, 100days)
- Scotch Bonnet: 100,000-580,000 SHU (OP, 120 days)
- Habanero: 100,000-500,000 SHU (OP, 90-100 days)
- Jamaican Hot: 100,000-200,000 SHU (OP, 95 days)
- Chiltepin: 100,000 SHU (OP, 95 days)
- Thai: 50,000-100,000 SHU (OP, 90 days)
- Cayenne: 30,000-50,000 SHU (OP, 72 days)
- Aji: 30,000-50,000 SHU (OP 85-90 days)
- Tabasco: 30,000-50,000 SHU (OP, 80 days)
- Serrano: 8,000-23,000 SHU (OP, 75-80 days)
- Mirasol: 5,000 SHU (OP, 100 days)
- Jalapeño: 2,500-9,000 SHU (OP, 75 days)
- Fresno: 2,500-8,500 SHU (75 days)
- Hungarian Wax: 1,000-15,000 (OP, 70 days)
- Ancho: 1,000-2,000 (OP, 76-80 days)
- Poblano: 500-2,000 SHU (OP, 75-80 days)
- Santa Fe: 500-700 SHU (75-80 days)
- Anaheim: 250-1,400 SHU (OP-75 days)
- Pepperoncini: 100-500 SHU (OP, 62 days)
- Paprika (several peppers are used for paprika) 50-200 SHU
- Pimento: 0 SHU (OP, 100 days)
- Sweet Banana: 0 SHU (OP, 72 days)
- Sweet Bell: 0 SHU
Get tips on how to grow hot peppers at How to Grow Peppers.