Organoleptic Testing vs HPLC
The original Scoville test uses human tasters to measure how much sugar water it takes to neutralize the burn. HPLC (High-Performance Liquid Chromatography) measures capsaicinoid concentration directly. HPLC is objective and precise; the Scoville test is subjective but gave us the scale we still use.
Scoville's original method
Wilbur Scoville's 1912 organoleptic test: dissolve a pepper extract in sugar water, dilute it in increasing ratios, and have a panel of tasters report when they can no longer detect heat. The dilution ratio becomes the SHU rating. A jalapeño takes about 5,000 dilutions; a Reaper takes 2.2 million.
HPLC method
High-Performance Liquid Chromatography separates and quantifies individual capsaicinoids by pushing a dissolved sample through a column at high pressure. Each capsaicinoid produces a distinct peak on the chromatogram. The peak areas are converted to SHU using a standard multiplier (typically 16.1M SHU per gram of capsaicin).
Why we still say SHU
HPLC measures capsaicinoid concentration in ppm (parts per million) or ASTA pungency units. But the pepper world still uses SHU because Scoville's scale is intuitive — 'this pepper is 2 million' means something to people in a way that '128 ppm total capsaicinoids' doesn't.
How Scoville Splice measures
All Scoville Splice specimens are measured by HPLC with results reported as both total capsaicinoids (ppm) and the equivalent SHU. The five-capsaicinoid breakdown (capsaicin, dihydrocapsaicin, nordihydrocapsaicin, homodihydrocapsaicin, nonivamide) is reported for every specimen.
Organoleptic (Scoville) Test
Wilbur Scoville's 1912 organoleptic test: dissolve a pepper extract in sugar water, dilute it in increasing ratios, and have a panel of tasters report when they can no longer detect heat. The dilution ratio becomes the SHU rating.
HPLC Analysis
A jalapeño takes about 5,000 dilutions; a Reaper takes 2.2 million.