Chilli heat and pungency on pizza

Short answer

Chilli heat comes from capsaicin, which triggers the body's heat-and-pain receptor rather than a taste, so a small amount tends to lead the whole pizza and linger. Sweetness and dairy tend to temper it. Raw garlic's bite comes from allicin, an unstable compound that cooking largely destroys, so garlic baked or roasted is far milder than garlic added raw. Black pepper acts on the same receptor as chilli; rocket's pepperiness comes from different compounds again and varies from leaf to leaf. Chilli oil and fresh chilli keep most character added after the bake; 'nduja goes on before so it can melt and spread.

What is actually happening

Capsaicin, the active compound in chilli, activates TRPV1, a receptor on pain-sensing nerves that also responds to painful heat — which is why chilli is felt as burning rather than tasted, and why the sensation builds with each bite and lingers after swallowing. Piperine, the pungent compound in black pepper, activates the same receptor in laboratory studies, so pepper's sharpness is a relative of chilli burn rather than a separate taste. Raw garlic is different: crushing or cutting it produces allicin, one of the sulphur compounds (thiosulfinates) responsible for its bite, and raw garlic extract activates both TRPV1 and a second pain receptor, TRPA1. Allicin is unstable, and baked garlic in the same study did not activate either receptor — the laboratory basis for the familiar observation that roasted garlic is mellow. Onion's sharpness also comes from sulphur compounds formed on cutting and also fades with cooking. Rocket's heat and pepperiness are tied to its glucosinolates and the isothiocyanates they release, vary markedly between varieties, and seem weaker where the leaf is relatively sweet. In a controlled study, milk (skim as well as whole) and a sweet drink reduced chilli burn more than water or carbonated drinks; on a pizza, honey, sweet onion, ricotta or burrata next to the chilli are applying the same directions, though the study used drinks, not toppings.

What it changes

Each claim below is deliberately hedged. PizzaHQ's sensory vocabulary has no “always” — the strongest statement available is “usually”.

What it does not change

Tempering is not removal: honey or burrata changes how the burn is perceived, not how much capsaicin is on the pizza. Cooking clearly mellows garlic and onion, but PizzaHQ has no source showing that a pizza bake does the same to chilli, so do not count on the oven to tame a hot chilli. None of this predicts how hot a particular chilli, salami or 'nduja is — that varies by product and batch — and the receptor studies say nothing about how pungent a given pizza will seem.

Where this becomes a matter of taste

Sensitivity to chilli and to raw garlic differs a great deal between people, and so does liking: for some the burn is the point of the pizza, for others any heat spoils it. Sensitivity to the bitter side of rocket also varies between individuals. The mechanisms explain why a little goes a long way; they do not say how much is too much for you.

In practice

• Add heat in a small amount first — it outweighs its share of the pizza, and more can always go on at the table.
• If a pizza turns out hotter than wanted, honey, ricotta or burrata near the chilli, or a glass of milk, tends to help more than water or a fizzy drink.
• For a sharp garlic hit, add raw garlic after the bake; for a gentle one, roast it or stir it into the oil or sauce under the cheese.
• Put 'nduja on before the bake in small dollops so it melts and spreads; spoon chilli oil or fresh chilli on afterwards to keep its aroma.
• Taste the rocket before piling it on — its pepperiness varies from bag to bag.

Related

Evidence

• The capsaicin receptor: a heat-activated ion channel in the pain pathway — Nature 389:816–824 (doi:10.1038/39807)
• Effects of piperine, the pungent component of black pepper, at the human vanilloid receptor (TRPV1) — British Journal of Pharmacology 144(6):781–790 (doi:10.1038/sj.bjp.0706040; open access, PMC1576058)
• The pungency of garlic: activation of TRPA1 and TRPV1 in response to allicin — Current Biology 15(10):929–934 (doi:10.1016/j.cub.2005.04.018)
• The influence of phytochemical composition and resulting sensory attributes on preference for salad rocket (Eruca sativa) accessions by consumers of varying TAS2R38 diplotype — Food Chemistry 222:6–17 (doi:10.1016/j.foodchem.2016.11.153; open access, PMC5243146)
• Putting out the fire — efficacy of common beverages in reducing oral burn from capsaicin — Physiology & Behavior 208:112557 (doi:10.1016/j.physbeh.2019.05.018)