Colorimetric determination of capsaicin in local chili in Nakhon Ratchasima Province

Abstract

The objective of this project was to determine the capsaicin in local chili in Nakhon Ratchasima Province with colorimetric detection based on the reaction between capsaicin and phosphomolybdic acid under alkaline condition. The phosphomolybdic acid was reduced by capsaicin to molybdenum blue producing blue solution. The absorption was monitored at the wavelength of 650 nm. The conditions of analytical method were optimized including concentration of phosphomolybdic acid, concentration of sodium hydroxide and reaction time. Under optimum conditions, this method provided high precision (%RSD=1-3) and accuracy (%Recovery = 80-100). The linear range concentration was 2-40 mg/kg. The limit of detection and limit of quantitation were 2 mg/kg and 5 mg/kg, respectively. The results showed that every species of chili at ripen stage provided higher concentration of capsaicin than those of raw stage. In addition, the concentrations of capsaicin in chili were relied on chili species ranging between 22-4,517 mg/kg.