Pure capsaicin rates 16 million Scoville heat units, while resiniferatoxin from euphorbia sap is estimated at 16 billion. This episode explores how we try to measure spice, starting with pharmacist Wilbur Scoville’s 1912 organoleptic test, in which a panel of five tasters sipped diluted pepper extracts until most could no longer detect heat.

We explain how capsaicin lowers the firing threshold of TRPV1 receptors so body temperature feels like burning, why sensory fatigue made early results vary by up to 50 percent, and how high performance liquid chromatography replaced human tasters. We also look at why dry mass ratings mislead, how growing conditions change pepper heat, and climb the scale from bell peppers to the Carolina Reaper and Pepper X.

• How Scoville’s dilution method worked and why tasters’ biology made it unreliable
• The role of substance P and neural adaptation in numbing the palate
• How HPLC counts capsaicin and dihydrocapsaicin and converts ASTA pungency units to Scoville units
• Why fresh peppers are about 90 percent water and why stressed plants produce hotter fruit
• Estimated ratings for non-capsaicinoid compounds like piperine, gingerol, and resiniferatoxin