Solubility of capsaicin and dilution

The FoodSense - ChilliPot from  ZP is a fast and easy instrument able to measure the hotness of chili, the pungency of garlic, the gingerness of ginger, the curcumin in turmeric, the sulfite in wine, the pH and E. coli.

In this note we discuss measuring the hotness of chili products and the impact of capsaicin solubility on the necessary dilution when using the FoodSense for measuring the hotness of chili and chili products.

In order to 'make FoodSense fast and easy to use we  have minimized and simplified the sample preparation, for example by 'saying' add one volume of sample to 1 volume to 4 volumes of buffer. The contrast to this are the HPLC methods where the sample extraction time can be five hours in refluxing/boiling solvent.

In many of our videos we see that we use the 1:4 dilution of sauce/product to buffer, often works for sauces and salsa, but in the case of hot powders, pastes and resins then the 1:4 dilution is not necessarily recommended. It comes down to the fact that capsaicin has a limited solubility of approximately 29 mg/L ( approximately 29 ppm). This means that the most capsaicin you can have dissolved in pure water is theoretically 435 Scoville Heat Unit (SHU).  The pH and other things in sample like fats and oils increase this solubility of 29 ppm/435 SHU to a higher value, the final solubility limit depends on the sample itself; is it an oil, paste, resin etc. Clearly adding alcohols/organic solvent to the water also increase solubility and extraction efficiency, but at FoodSense we have not used organic solvents as these can increase the risk to the user, and it is not necessarily appropriate to have solvents around food manufacturing.

 At FoodSense, if we think the sample is 'mild, medium, hot or extra hot' then we change the dilution accordingly. For samples that are 'mild' we use a low dilution and for sample that are extra hot we use a higher dilution, in accordance with the table