Scoville Units in Peppers

by Kelly Kellow, Horticulturist and Greenhouse Manager, Gardens on Spring Creek

Ever wonder what makes a pepper hotter than the next?  Why one burns your mouth so badly that you need milk while the other doesn’t?  Peppers have this amazing chemical called capsaicin.  Capsaicin is a chemical component of chili peppers that gives them their heat.  It is a colorless, odorless, oil-like compound found in the fruit.  It is not in the flesh part of the pepper but is concentrated primarily in the capsaicin gland – the midrib of the membrane that holds the seeds.  

Peppers’ heat is determined and ranked on the Scoville scale.  It is named after Wilbur L. Scoville (1865-1942), who developed the Scoville Organoleptic Test in 1912 as he attempted to find a suitable pepper for use in a heat-producing ointment.  The scale is used to measure the total amount of capsaicin in peppers.  

The newest technology for figuring out true Scoville units requires high-performance liquid chromatography that determines the exact concentration of capsaicin.  However, many experts and heat lovers still love to be a part of the traditional way of measuring Scoville Heat Units (SHU) of peppers – through taste testing!

To complete this, an individual dried hot pepper gets an alcohol extraction of capsaicin oil that is mixed with a solution of sugar and water.  A panel of human taste testers then get drops of this solution until they can’t detect the heat of the pepper.  The pepper is then assigned a SHU with respect to the dilution required for the “burn” to no longer be sensed.  For example, if a pepper has 5,000 SHU, the oil obtained from the extract must be diluted 5,000 times before the heat is barely detectable.  The accuracy for this has many different factors, including how the pepper was grown and, of course, the tolerance of the taste-tester.  Additionally, some peppers may be hotter than others, even if they come from the same batch.  I know I have ordered an appetizer of jalapeno poppers, and one always seems to be hotter than the others. This taste testing is less common in determining the SHU but can be fun for those that love the heat! 

Peppers from all around the world range from 0 to more than two million SHU.  

• Sweet Bell P:  0 SHU
• Jalapeno:  2,500 – 8,000 SHU,
• Habanero:  100,000 – 350,000 SHU
• Carolina Reaper:  400,000 – 2.2 million SHU – holder of the Guinness World Record

Today, breeders have been working on the next hottest pepper, known as the Primotalii Pepper.  It doesn’t have an official SHU rating, but it is no doubt one of the hottest and is most likely over 2.2 million.  For reference, pure capsaicin is ranked as 15 million, with United States-grade pepper spray at 5.3 million SHU.  

Competition between the hottest peppers will never stop as breeders are constantly trying to grow the next hottest pepper for that “hurts so good” flavor.