Red Pepper Flakes: What’s in the Jar, How Hot They Are, and How to Use Them

Red pepper flakes, also sold as crushed red pepper, are the shaker on the pizzeria table and a quick hit of heat for almost anything. They’re dried red chiles broken into coarse flakes, seeds and all, and in the United States the chile is usually cayenne, alone or blended with other cultivars. How hot they are is murkier than you’d think: the 30,000 to 50,000 SHU figure you see everywhere has no traceable source. And Turkey’s flakes, pul biber, come with a legal limit on how much of the jar can be seeds.

At a glance

What red pepper flakes are

Under the international standard for dried chile (Codex CXS 353-2022), dried chilli and paprika can be sold whole, “crushed/cracked/broken/flakes”, or ground, with or without seeds or stalks.² Red pepper flakes are the crushed style.

What goes into a particular jar is up to the maker. McCormick Science Institute says crushed red pepper flakes typically use the cayenne variety alone or blended with other cultivars, and that most commercially available red pepper is Capsicum annuum.³ It describes the dried flakes as orange-red to deep dark red, often with visible yellow seeds. PepperScale also describes the typical jar as a mix of chiles with the seeds left in: cayenne most often, with chile de árbol or ancho among the others.⁴ You’ll often read that jalapeños, serranos and Anaheims are standard ingredients and that blends contain three or four cultivars. None of the sources we checked shows either.

Where the heat sits. Researchers at The Ohio State University describe capsaicinoids building up in small structures called blisters that form along the inner walls of the fruit (the interlocular septum).⁵ The popular idea that the heat lives in the seeds themselves isn’t what that source describes.

Turkish pul biber, isot and Balkan flakes

Several countries make their own flakes, and at least one regulates them closely.

Turkey. The Turkish Food Codex communiqué on spices (2022/7) defines pul kırmızıbiber (pul biber) as red pepper conditioned with water and ground or broken into flakes of different sizes, with edible vegetable oil and salt allowed.⁶ Its limits:

So standard pul biber can legally contain a fair share of seeds. It’s the “silk” grade, ipek, that’s nearly seed-free. You’ll often read that pul biber is made only from the pepper walls. The Turkish standard doesn’t say that.

The same communiqué defines isot: red pepper conditioned with water, broken, held at 70 to 80 °C for 3 to 12 days, and mixed with vegetable oil and salt.⁶ It’s a different product from ordinary dry flakes.

North Macedonia. Slow Food has backed a Presidium for the Bukovo red pepper, which was close to extinction. The peppers dry on strings hung beside farm buildings for about three months and are often crushed into flakes or powder, still by hand.⁷ It’s widely claimed that red pepper flakes were invented in the village of Bukovo and that the words for chile flakes in several languages come from its name. None of the sources we checked supports either claim.

Korea. Gochugaru comes as coarse flakes and as powder. See its page for heat and history.

How hot are red pepper flakes?

The figures below come from different kinds of sources and measure different things, so they’re listed side by side and not combined:

How to read this:

• The Codex figures are category boundaries, the lines a product has to meet to be labeled chilli instead of paprika or hot paprika. They aren’t measurements of any jar.²
• The 30,000 to 50,000 range is untraceable, not wrong. We found no study, standard or named measurement behind it. McCormick Science Institute says cayenne powder is usually hotter than flakes, with cayenne itself at about 8,000 SHU, and that doesn’t sit easily with the bigger number.³ But neither source states its samples, so there’s no way to settle it. PepperScale gives 30,000 to 50,000 SHU for cayenne powder, not flakes, and says the flakes won’t come near it.⁸ The widely repeated figure may be a cayenne range that got attached to the flakes, though no source shows that.
• Heat varies by chile and by lot. Scoville taste tests are subjective. High-performance liquid chromatography (HPLC), which measures the heat compounds directly, is the most accurate method.¹ Retail jars rarely state either.

For the cultivar measurements behind cayenne, see cayenne pepper.

Flavor

Flakes taste of dried red chile with a quick, sharp heat. The seeds add a little nuttiness and texture, and the heat comes in small bursts instead of evenly the way a fine powder’s does. Each blend’s character depends on its chiles.

Origin and history

Chiles are New World plants. Capsicum annuum is native from the southern United States to Brazil and the Caribbean, and a 2014 study combining genetics, ecology, archaeobotany and linguistics points to domestication in central-east Mexico.⁹ Once red peppers reached Europe, Portuguese traders spread them quickly through Asia.

We couldn’t trace several stories told about red pepper flakes: that southern Italians took them up in the 19th century, that early Italian immigrants brought them to the United States and the oldest Italian-American restaurants served them, and that China and Turkey are the top producers. They may be true. None of the sources we checked shows them.

How they are used

• At the table. Red pepper sits on kitchen tables in many households, as a finishing sprinkle for pizza, pasta, soups, sandwiches, salads and anything that wants a dash of heat. See good spices for pizza.
• Chili oil. Steep the flakes in hot oil with other spices, and their heat and color carry into the oil.
• Pickles. Crushed red pepper adds color and heat to pickle brines.
• Meats, seafood and blends. Red pepper goes into seasoning blends, meats, pickles and seafood, and into Italian, Indian, Mexican and Caribbean cooking. Italian sausage is a familiar example.
• In cooking. Flakes go into the oil with garlic at the start of a pasta sauce or stir-fry, where the heat spreads through the whole dish. Added at the end, they stay sharper and easier to see. Start with about ¼ teaspoon for a dish that serves four and adjust from there. We found no measurement of that, so let your taste decide.

For more ideas, see cayenne pepper uses.

Buying and quality

• Color. Look for bright orange-red to deep red flakes. Brown, dull flakes have probably lost color and aroma.
• Seeds. Lots of pale seeds is normal in American flakes. If you want fewer, Turkish ipek pul biber is held to 2% seeds by its standard.⁶
• Salt and oil. Turkish pul biber and isot can contain added salt and oil within the codex limits,⁶ so check the label before you salt the dish.

Storage

Keep flakes airtight, away from light and the stove. We found no shelf-life figure from a regulator or standards body for red pepper flakes, and we couldn’t trace the figures that circulate online. When the color’s gone dull and the flakes don’t smell like much, replace them.

Nutrition and health

We didn’t check a USDA nutrient entry for crushed red pepper, and you use flakes in amounts too small to matter much nutritionally anyway. None of the sources we reviewed supports claims that they prevent or treat diabetes, prostate cancer or constipation.

Capsaicin. The strongest human evidence on capsaicin is about a prescription skin patch, not chile in food. A 2017 Cochrane systematic review found moderate-quality evidence that a high-concentration (8%) capsaicin patch gave moderate pain relief to a minority of people with postherpetic neuralgia.¹⁰ We’re not claiming red pepper flakes treat or prevent any disease.

Safety

• Mycotoxins (EU). EU law caps ochratoxin A at 20 µg/kg in dried Capsicum fruits, a category it says includes chillies, chilli powder, cayenne and paprika, and sets 5.0 µg/kg for aflatoxin B1 and 10.0 µg/kg for total aflatoxins.¹¹
• Handling. Keep flakes away from your eyes and wash your hands after handling them.

Substitutes and comparisons

• Red pepper flakes substitutes
• Ground chiles: cayenne pepper, chile de árbol powder, paprika, chili powder
• Other flakes: gochugaru
• Black pepper vs. cayenne