You might have already heard of the Scoville scale. But something you’ve probably noticed is that not every hot sauce bottle in your favorite restaurant has a scoville rating printed on the label. Why is this scale important? What are Scovilles? And why don’t you see it more publicly in the wild? This guide will give you some context to the creation, use, and limitations of the Scoville scale in the world of hot sauces.
Think of the scoville scale as a pungency scale, measuring spiciness or the “heat” levels of spicy things, like chili peppers. The individual measurements of this scale are called Scoville Heat Units, or SHU, but you might hear people refer to them colloquially as just “Scovilles.”
The scale has been used for over a century now, as it was invented by Wilbur Scovile in 1912. Depending on the amount of capsaicin in what you eat, the Scoville Scale will give you an idea of the sensation of heat to expect when eating, say, a hot pepper. Capsaicin is a natural chemical that makes your tongue burn, body sweat and ears ache!
When testing peppers and rating them on the Scoville scale, a dried pepper at an exact weight is dissolved in alcohol. The alcohol helps extract the capsaicin oil from the hot pepper, which is then mixed in sugar water. The next steps are a series of dilutions: the extracted capsaicinoids are diluted in declining concentrations and given to trained taste testers. The job of these taste testers is to taste these concentrations until they can’t “feel” the heat anymore. The final dilution is rated on the Scoville scale by a factor of 100 SHU.
For example, the carolina reaper pepper is rated at 2.2 million SHU, which means it would need to be diluted 2.2 million times before the heat would no longer be detectable. In comparison, a jalapeño is usually between 2,500 to 8,000 SHU!
Despite its popularity across the hot sauce industry as a method of measurement, the Scoville Scale is not one without limitations.
You have probably met people who have an extremely high spice tolerance level. On the other hand, you might bite into a jalapeño and immediately need some water to disperse the heat. Everyone is different, and even trained Scoville taste testers will always have their own spice tolerance levels that differ from their peers.
This is why the current method of “taste testing” is problematic. Even though some current scoville tests try to remedy the subjectivity of this method by using 5 taste testers, it still does not eliminate the subjectivity of each individual tester’s spice tolerance. At the same time, if the same 5 testers are used and no rotation happens, their palate can develop a tolerance to even the spiciest capsaicin solutions out there.
Hot sauce ingredients like vinegar and the water content in a pepper can significantly skew SHU ratings during testing.
Let's say the manufacturer of a hot sauce wanted to advertise its Scoville level. This manufacturer would most likely get their hot sauce tested, which happens through a dehydration process. The dehydrated powder will be tested and rated at 1,000,000 SHU. However, if vinegar was added to this sauce in a set ratio, say 1 part vinegar for 1 part hot pepper, this vinegar evaporates during the dehydration process. The existence of vinegar in the hot sauce would mean that the 1,000,000 SHU rating does not account for the vinegar dilution. A more accurate SHU rating that accounts for the dilution would be a much lower number, around, say 500,000 SHU.
Additionally, fresh peppers used in hot sauce production are usually 90% water. This would further dilute the SHU rating, and make it closer to 50,000 SHU. The problem is not that these tests are inaccurate or wrong, but rather that different companies will report different SHU numbers depending on their awareness of dilutions. Usually, the lowest number is the most accurate, since it accounts for all possible dilutions from ingredients used in the sauce itself.
The first form of more accurate capsaicin concentration evaluation is called High Performance Liquid Chromatography (HPLC). It is regarded as a more scientific and accurate method of measuring and rating capsaicin concentration in hot peppers, since it relies on machines, not human taste testers.
During HPLC, the capsaicin extract is pumped through a machine. This machine contains layers of absorbent material, and each element of the extract will interact differently with these materials. In the end, overall flow rates are measured, and are assigned a pungency unit.
HPLC is the American Spice Trade Association’s preferred method of measuring capsaicin concentration. HPLC measurements are assigned “ASTA Pungency Units,” where 1 ASTA unit equals around 15 SHU. On the whole, HPLC results are more reliable, accurate, and are usually 20% to 40% lower than Scoville ratings.
Ivette Guzmán and Paul W Bosland, researchers and authors of the journal “Appetite”, devised a way to evaluate and classify peppers based on 5 distinct sensory qualities. These 5 sensory qualities are:
This method of evaluating spice levels and pepper qualities is a far more comprehensive assessment of what goes into the sauce. It doesn’t simply rely on just the SHU to give the entire picture of the pepper, it also is aware of the relationship between varieties of capsaicin compounds and their relationship to how our taste receptors interact with them.
Industry-wide, the Guzmán and Bosland method can also be used to determine which chilli pepper varieties would be best suited for different cuisines or cultures. Some cultures might prefer more intense, sharp qualities that rapidly take over your mouth but disappear just as quickly. Other cultures might favor more moderate ramping up of heat, and can adjust their preferences based on the info from this method.
While the Scoville scale is a popular choice in the hot sauce world to measure capsaicin concentration, it does come with its own set of limitations.
Taste testers are far too subjective to determine an accurate SHU number for most peppers. This is because each tester’s existing spice tolerance is different, and their spice tolerance will increase over extended periods of testing.
Ingredients in hot sauces like vinegar, or the existing water content of peppers themselves also need to be reflected in testing, but cannot be guaranteed to be 100%. This is because these ingredients actually dilute capsaicin concentrations, and aren’t always reported.
Finally, more scientific and holistic evaluation methods exist. HPLC uses machines to report capsaicin concentrations instead of humans, creating more accurate and calculated results. Guzmán and Bosland’s method evaluates 5 pepper qualities, and diverts the focus away from just using a SHU number.
All in all, the Scoville scale is useful as a popular industry standard of measurement, but not as the sole method of determining heat levels in hot peppers or hot sauces.
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