Humanity’s love of spice and heat is so strong that we have sought it out wherever we are, in whatever way we can find it. We’ve used spices like pepper, chillies and tingling Sichuan peppercorns as well as fresh aromatics like ginger, garlic and horseradish. We’ve dried it, smoked it, powdered it, fermented it – everything you can think of. However, there are noticeable differences in the type of heat each ingredient provides. The throat-tingling sting of ginger is not the same as the nose-burning heat of horseradish. So if you’ve ever wanted to learn more about exactly what spiciness even is, read on. 

It makes sense to start with black pepper, the most ubiquitous spice on British dining tables. While there are hot ingredients that are native to Europe, like mustard and garlic, beloved black pepper is native to South India. It was one of the earliest spices to be imported to Europe, having been used in Ancient Greece since 500 BCE. Black pepper was so prized and expensive that nearly 1000 years later, when the visigoths ransacked Rome in 410 AD, they demanded this 'black gold' as ransom.

Pepper’s distinctive, well, pepperiness comes from the chemical compound piperine. Green, white and black peppercorns, like green, white and black tea, all come from the same plant, and so all contain piperine, while pink peppercorns' heat is slightly different. Piperine is also found in long pepper, a separate, delicious species which is well worth seeking out. 

Despite not being so common in savoury recipes, the combination of sweet molasses and fiery ginger is at the heart of many renowned British desserts. Gingerbread, ginger beer, gingerbread men – the list goes on. One of ginger’s most interesting properties is that its heat changes depending on whether it is served raw, cooked or dried. Drying or cooking ginger causes a chemical reaction in the rhizome that makes it more or less spicy respectively. So, if you’re after a less spicy and more aromatic cake, try using some fresh ginger instead of ground ginger.

Whereas the fragrance of black pepper, cardamom and nutmeg has long been associated with prestige, garlic’s smell has historically been looked down upon. It’s quite well known that Italian migrants to the UK and US were labelled ‘garlic eaters’, but what’s less well known is that eating too much garlic was also highly stigmatised within Italy. This could be because of garlic’s ubiquity: unlike many aromatics and spices, garlic is native to Europe and has always been affordable and fairly easy to grow.

Any home cook who has used garlic is likely to have noticed that garlic’s pungency depends on how it's prepared. Microplaned raw garlic is strong enough that even a touch in a vinaigrette will be immediately apparent, while confit garlic cloves can be eaten whole, straight from the jar. This variability is due to two main factors. One is that allicin, the sulphur-containing compound that gives garlic its burn, is only produced when you break down the cell walls of garlic. The more garlic cells are crushed (through grating or fine chopping) the stronger its aroma. So, grated garlic has a stronger flavour than sliced garlic. The other factor is heat. Unlike chillies and ginger, cooking garlic completely removes its spiciness, rendering it mild and gently fragrant. The same is true of alliums like leeks, shallots and onions, which all become sweet and gentle when cooked.

For the most part, when someone says ‘spicy’ they’re thinking of chillies. And with good reason – no other plant comes close to the fierceness of a Scotch bonnet, let alone a Carolina reaper. Chillies’ heat can’t be tamed by drying, stewing or frying, so if you're using chillies in any form, you're looking for heat.

The heat of chillies comes from capsaicin, a compound produced in the white pith that attaches the seeds to the flesh (technically called, rather disconcertingly, the placenta). Unlike mustard and garlic, which cause a mild but very real irritation in the throat, the burn of capsaicin is ‘all in your head’. Capsaicin binds to pain receptors called TRPV1, which then send signals to the brain that your mouth is too hot. This is the opposite of what happens when you try something mentholated – that causes your mouth to feel like it's cooling.

Unlike with mustard or garlic, you can build up a tolerance to spice over time. So if you feel like you’re unable to try certain delicious spicy food, there is hope! Start small with milder chillies and work your way up.

All the other spices on this page have one thing in common: they mostly affect your mouth. Mustard, as anyone who’s accidentally bitten into a blob of the stuff knows, goes right up your nose. This is because the burn in mustard comes from a different class of chemicals, called isothiocyanates. All plants in the cabbage family – cabbage itself, horseradish, wasabi etc. – contain these nose-tingling compounds. Unlike with chillies, where the heat always comes from capsaicin, different types of mustard burn in slightly different ways. Black and brown mustard contain the most pungent compound, sinigrin, while yellow mustard and wasabi contain the slightly milder sinalbin.

Last but certainly not least, the infamous Sichuan peppercorns – which are in fact not peppercorns at all. Sichuan peppercorns are actually the dried husk which surrounds the berry of the prickly ash tree. The peculiar buzzing sensation they produce on the lips and tongue is beloved in, but by no means unique to, Sichuan. The sensation which Sichuan peppercorns produce is sometimes called ‘numbing’ after the Chinese term mǎlà (麻辣 numbing-spice). It’s hard to describe if you’ve never had Sichuan peppercorns, but the food scientist Harold McGee compares it to drinking something highly carbonated – or even licking a battery.

Both Sichuan peppercorns and the lesser known Japanese sanshō produce this tingling, thanks to the chemical compound sanshool. Sanshool attaches to pain receptors (like capsaicin) but also inhibits certain types of potassium channels in the mouth. This is probably the cause of the addictive buzzing sensation.

If all of this talk of heat has made you crave spicy food, why not check out this list of the seven hottest recipes on our website.