A simple and rapid electrochemical determination of pungency: Application to aqueous and ethanolic extracts of Capsicum annuum cubana red

Abstract

Chili peppers are rich in ascorbic acid and capsaicin. In this article is proposed an easy, fast, sensitive, and inexpensive method for determining the pungency and content of ascorbic acid in chili pepper extracts. The voltammetric (cyclic and differential pulse) behavior of capsaicin on a glassy carbon electrode has been evaluated at different pH values. A calibration curve has been obtained for the peak current, IP, of capsaicin as a function of the capsaicin concentration, C, in differential pulse voltammetry in phosphate buffer solution at pH 7.0: IP(µA) = 0.0147 (±5.346·10−3) + 0.0507 (±8.984·10−4) C(µM), with limit of detection, LOD = 0.198µM, limit of quantification, LOQ = 0.660µM, and dynamic linear range from 0.660 to 20.9 µM. A variant of the standard addition method has been used for simultaneous determination of the pungency and ascorbic acid content of extracts of Capsicum annuum cubana red. In this case, the calibration for ascorbic acid was I(µA) = 0.467 (±0.012) + 2.039·10−3 (±4.601·10−5) VAA(L)), with LOD = 17.56 µL, LOQ = 58.55 µL, and dynamic linear range from 58.6 to 500 µL, being VAA the volume of 10-mM ascorbic acid added to 50 mL of solution. The ascorbic acid content was compared to that of a sweet pepper. The method is cheap, simple, and fast (30 min vs c.a. 2 h compared to the spectrophotometric method), its sensitivity being comparable to other more expensive and/or more laborious methods.