The world loves spicy food. From the curries of Asia to the wat's of East Africa, people have been turning up the heat in the kitchen for centuries. In recent years, as our understanding of biology has advanced, something of an arms race has developed among top chilli breeders. Each new year brings intense competition and the eternal battle to produce the next ludicrously hot pepper shows little sign of abating.
However, it is not just chillies that can be used to up the spice our cooking. Other naturally occurring spices offer a similarly potent, if not necessarily nuclear effect on the palate. We've taken a closer look at some of the planet's hottest ingredients.
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1. Chilli
You can’t have a conversation about heat without first discussing chilli. A near ever-present in spicy Asian, African and American cooking, chilli peppers have been bred into a startling number of varieties, each offering something unique. They range from the mild jalapeno to the infernal ghost pepper. Chillies derive their heat from the chemical capsaicin, which creates a burning effect, affecting the mouth, eyes and skin when consumed.
The potency of chilli peppers is measured on the Scoville scale, which ranges from 0 to 16,000,000 (the strength of pure capsaicin). The current hottest chilli in the world is the “Dragon’s Breath”, weighing in at an astonishing 2,480,000 units - 480,000 more than military grade pepper spray. Since no human has actually eaten this chilli yet, it doesn’t necessarily count as an ingredient. However, with terrifying prospects like the ghost chilli (1,000,000 SHU) used regularly in hot sauces and novelty dishes the world over, chillies are the undoubted kings of heat.
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2. Wasabi
Despite the world’s obsession over hot chillies, they do not have total ownership of the spice market. There are other, perhaps less lethal, but in their own way piquant ingredients. One such example is Japanese favourite wasabi. Sometimes known as Japanese horseradish, and often replaced with the Western root in restaurants due to the scarcity of true wasabi, the plant has been used for centuries to add heat to a variety of Japanese dishes.
Wasabi does not contain any capsaicin, and instead derives its heat from the volatile chemical allyl isothiocyanate (AITC). This chemical inflicts and causes a different effect than chilli peppers, instead irritating the nasal passageways and throat with a floral pungency. In the natural world, it is produced by plants as a defence mechanism to repel herbivorous animals, highlighting how potent the heat can be.
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3. Horseradish
Though Asia and Central America traditionally dominate discussion about spicy food, Europe is not without its own hot ingredients. A traditional exemplar is the aforementioned horseradish. Closely related to wasabi, horseradish is a small, nondescript plant, sporting small white flowers and typically growing to around 1.5 metres in height. It is prized in cooking for its root, which when grated releases large concentrations of AITC.
Horseradish is typically served as a sauce, preserved in vinegar. Though these sauces can be extremely strong, the volatility of AITC means that they lack the power of fresh horseradish. A staple condiment in central European cooking, horseradish is a great way to add a tempered heat to a meal.
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4. Mustard
Though many people will be familiar with this condiment as a yellow, vinegary ooze to be slathered with abandon on hot dogs and burgers, mustard can be something far more hostile. Prepared in a variety of ways around the world, the sauce is derived from the seeds of the mustard plant. The hottest example is English mustard, which has a thicker consistency than American counterparts and a strong, acidic tang and heat.
Mustard is perhaps most infamously associated with the chemical weapon mustard gas, frequently used during the First World War. Named for its yellow hue and similar smell, the weapon is not actually derived from mustard itself. However, that anyone made such an association shows how potent true mustard can be.
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Careful breeding and natural variation has meant that chillies still rule the roost when it comes to heat. However, there are clearly alternatives available for those who want to experience a different type of heat. Take note, however: none should be taken lightly. 
