What Actually Makes Chillies Hot?
Chilli heat isn’t caused by capsaicin alone. It comes from a group of compounds called capsaicinoids — primarily capsaicin and dihydrocapsaicin — which together shape both the intensity and the way heat is experienced.
Capsaicin vs Capsaicinoids: What Actually Makes Chillies Hot?
Most people think chilli heat comes down to one thing — capsaicin.
And while capsaicin is the main compound responsible for the burn, it’s only part of the story. In reality, chilli heat is created by a group of related compounds known as capsaicinoids.
This distinction matters more than most people realise. Two chillies can have a similar Scoville rating but feel completely different when eaten — one might hit fast and fade, while another builds slowly and lingers.
The reason comes down to the balance of capsaicinoids inside the chilli.
This article breaks down what capsaicinoids are, how they differ, and why they play a major role in how chilli heat is experienced in both cooking and food production.
What Are Capsaicinoids?
Capsaicinoids are a group of naturally occurring compounds found in chilli peppers (Capsicum species). They are responsible for the heat or “pungency” that chillies are known for.
All capsaicinoids share a similar chemical structure, but small differences between them change how they behave — particularly in how heat is perceived on the palate.
When people refer to “capsaicin,” they are usually referring to the dominant compound within this group. However, chillies contain a mixture of capsaicinoids, not just one.
These compounds are produced in the placenta of the chilli — the white internal tissue that holds the seeds — not the seeds themselves, which is a common misconception.
The Main Capsaicinoids Found in Chillies
Although there are several capsaicinoids present in chillies, a small number of them make up the majority of the heat profile.
Capsaicin
Capsaicin typically accounts for around 60–70% of the total capsaicinoid content in most chilli varieties. It delivers a sharp, immediate heat that is most noticeable on the tongue.
Dihydrocapsaicin
Dihydrocapsaicin is the second most abundant compound, usually making up 20–30%. It produces a similar intensity of heat but tends to linger longer, often contributing to the throat burn and afterheat.
Nordihydrocapsaicin
This compound is present in smaller amounts and is milder. It contributes background warmth rather than dominant heat.
Homocapsaicin and Homodihydrocapsaicin
These are minor capsaicinoids present in very small concentrations. While they don’t significantly increase overall heat, they contribute to the complexity and character of the chilli’s burn.
Together, these compounds create a combined heat experience rather than a single-dimensional sensation.
Why Different Chillies Feel Different
The way a chilli feels when eaten is not determined by total heat alone, but by how that heat is distributed across different capsaicinoids.
This is why two chillies with similar Scoville ratings can produce very different experiences. One may deliver an immediate, sharp burn that peaks quickly, while another may build more slowly and linger for an extended period.
These differences are shaped by the ratio of capsaicinoids, as well as other factors such as sugar content, acidity, and overall fruit composition.
From a practical standpoint, this is where chilli selection becomes more than just choosing a heat level. It becomes a question of how that heat behaves in the final product.
Applying Capsaicinoid Profiles in Sauce Making
For sauce makers, understanding capsaicinoids is not just theoretical — it has direct implications for how a product performs.
When working with fresh chillies, variability is unavoidable. Differences in growing conditions, ripeness, and handling can all influence capsaicinoid levels and ratios, leading to changes in both heat intensity and heat profile between batches.
This can make it difficult to maintain consistency, particularly as production scales.
Using chilli paste changes this dynamic. Because paste can be produced in controlled batches — and because different chilli varieties can be blended — it becomes possible to stabilise both total heat and the underlying capsaicinoid profile.
In practical terms, this means a sauce maker can:
- Balance fast, sharp heat with longer-lasting burn
- Blend different chilli types to achieve a specific flavour and heat profile
- Maintain consistency across batches
- Reduce variability caused by seasonal changes in fresh produce
Rather than relying on a single chilli and accepting its natural variation, blending allows for a more controlled and repeatable outcome.
This approach becomes increasingly important as production moves beyond small test batches and into commercial volumes.
Do All Chillies Contain the Same Capsaicinoids?
Most chilli varieties contain the same core capsaicinoids, but the ratio between them varies significantly.
This variation is one of the key reasons why different chillies feel different, even when they have similar Scoville Heat Unit (SHU) ratings.
For example, a chilli with a higher proportion of capsaicin may deliver a faster, sharper heat, while one with more dihydrocapsaicin may produce a slower, longer-lasting burn.
Environmental factors such as climate, soil conditions, water stress, and ripeness can also influence these ratios, meaning even the same variety can vary between batches.
In practical terms, this means that chilli heat is not just about how much heat there is — but how that heat is distributed across different compounds.
Scoville Rating vs Heat Profile
The Scoville Scale measures the total concentration of capsaicinoids in a chilli, expressed as Scoville Heat Units (SHU). However, it does not differentiate between the individual compounds.
This means two chillies can have the same SHU rating but feel very different when consumed.
For example, super-hot chillies like the Carolina Reaper are known for a slow-building, lingering burn, while varieties like Fatalii tend to produce a faster, cleaner heat. This difference is influenced by the balance of capsaicinoids rather than total heat alone.
One may produce a fast, aggressive heat that fades relatively quickly, while another may build gradually and persist for several minutes.
This difference is often referred to as the “heat profile” — and it is largely driven by the balance of capsaicinoids present.
Understanding this distinction is important for anyone working with chillies at a deeper level, particularly in sauce making and product development.
How Capsaicinoids Are Measured
While the Scoville Scale is widely used to describe chilli heat, modern measurement relies on analytical techniques that directly quantify capsaicinoids.
The most common method is High-Performance Liquid Chromatography (HPLC). This technique separates individual capsaicinoids within a sample and measures their concentration with a high degree of accuracy.
Unlike traditional Scoville testing, which was based on human taste panels, HPLC provides a detailed breakdown of each compound present — including capsaicin, dihydrocapsaicin, and the minor capsaicinoids.
This allows producers and researchers to understand not just how hot a chilli is, but how that heat is composed.
In commercial settings, this level of analysis is useful for quality control, product consistency, and formulation — particularly where repeatable results are required.
Is Capsaicin Ever Truly “Pure”?
Capsaicin is often referred to as the compound responsible for chilli heat, but when it is extracted from chillies, it is rarely isolated on its own without further processing.
Capsaicinoids are fat-soluble compounds, which means they can be extracted using solvents such as ethanol or through processes like supercritical CO₂ extraction. However, this initial extraction typically pulls out the full range of capsaicinoids, not just capsaicin.
The resulting material is often referred to as oleoresin capsicum — a concentrated extract that contains capsaicin, dihydrocapsaicin, and other related compounds.
To isolate capsaicin on its own, additional refinement steps are required. These may include chromatography or crystallisation techniques that separate compounds based on their chemical properties.
In most food applications, this level of isolation is unnecessary. The full spectrum of capsaicinoids is usually retained, as it contributes to a more complete and natural heat profile.
Final Thoughts
Chilli heat is often simplified to a single number, but in reality, it is shaped by a combination of compounds working together.
Capsaicin may be the most well-known, but it is the broader group of capsaicinoids — and their relative balance — that defines how heat is experienced.
Understanding this helps explain why different chillies behave the way they do, and why consistency can be difficult to achieve when working with fresh ingredients alone.
For anyone working seriously with chillies, particularly in sauce making or product development, thinking beyond total heat and considering heat profile opens up far greater control over the final product.