Extraction of capsaicin from Scotch Bonnet peppers and determination of the Scoville Rating
Posted by aonomus on February 17, 2010
So a soxhlet extractor has been on my list of ‘cool glassware to get’ (right next to an actual fractionation column out of glass, with real plates). I suppose the first experiment I can try is to extract capsaicin from habanero peppers, and then get a panel of friends to try serial dilutions of the extract to determine its Scoville heat rating.
Preface and Warnings
- Pure capsaicin powder in milligram amounts can cause severe skin blistering, burns, and reported nerve damage
- Oleoresin (the desired target of this procedure) can also cause severe skin blistering and burns.
- Use full personal protection equipment (lab coat, goggles, gloves) and have an eye wash ready
- Use a dust mask (preferrably N95) when handling dried peppers
- Start with 10 unripe Scotch Bonnet peppers, they should be firm, not leathery or soft.
- Cut peppers into quarters, separate out seeds manually (contains the largest amount of capsaicin), place into pyrex containers, chop peppers finely*. Place into an oven, and begin drying at minimum setting (preferrably under 100degC). *Ideally, a blender can be used once seeds have been separated.
- Remove seeds when dry, allow peppers to dry fully, stir as needed
- When fully dry, begin next procedure segment.
- Set up 250mL round bottom flask in heating mantle or water bath, add clean, new boiling chips, and 100mL 95% ethanol.
- Place soxhlet extractor onto flask, fluff 1 or 2 cotton balls and place at the bottom of the extractor (pack with a glass rod).
- Add dried seeds to extractor, and level out. Add pepper flesh until full* and level out. Place another 1-2 cotton balls ontop and pack gently with a glass stir rod.
- Fit adapter (depends on extractor construction) and condenser to the extractor. Begin heating to boiling.
- Maintain heating and replenishing water bath as necessary for 2 hours (typically until ethanol coming off the extractor is clear).
- Proceed to concentration step.
Note: at this stage, assuming a ideal sphere of 2cm radius with 10 peppers gives a volume of 335mL reduced to 100mL ethanolic solution. You can try to taste test this carefully, pipette off a small aliquot (approx 0.2mL) to a clean Eppendorf microtube, and use a clean qtip or coffee stirrer to sample a small portion and touch it to your tongue. You may notice that the spicyness is not very strong, however once fully concentrated, the extract will be hazardous to sample in this method. Do not try this with any higher concentrations of capsaicin extract.
- If available, use a rotary evaporator with a bump-trap to remove solvent.
- Set up a distillation apparatus, evaporate solvent under reduced pressure carefully to prevent bumping
- Allow concentrate to stand overnight in a sealed vial once cool. Oil will form separate layer.
- Use pasteur pipette to remove bottom oil layer (red-brown).
Characterization of Scoville Rating:
- A panel of 5 volunteers tasted 1:10 serial dilutions of the original concentrate in 5% sucrose.
- Spicy taste/sensation was noted at the 1:100 dilution by 4/5, and again at 1:10 with 4/5 (different individual as the negative result individual)
- Concentrate was tasted after concluded to be safe enough to try – volunteers noted that the concentrate was comparable to tobasco sauce.
- Avoid the vacuum distillation process, as some capsaicinoids could have been lost at this step
- Obtain better peppers, dry fully, and grind up well (this step was bypassed in lieu of filming the video quickly)
- Perform TLC to determine composition of dilute extract and concentrate.