engleski

Electrochemistry-based determination of pungency level of hot peppers using the voltammetry of microparticles

Hot peppers are among the most popular food additives, valued for their attributes of colour, aroma and, most of all, for their pungent flavour. The pungency is caused by capsaicinoids, and among the most abundant of these components in hot peppers are capsaicin and dihydrocapsaicin, which are responsible for about 90 % of spiciness. The level of pungency of hot peppers or other spicy foods is usually measured by Scoville Test, which is a subjective organoleptic test because it relies on the tester's perception of pungency. The most accurate method of calculating pungency in hot peppers is high–performance liquid chromatography (HPLC). Chromatographic methods are generally complicated, time-consuming and require expensive instruments. Electrochemical techniques, particularly voltammetry, are a promising alternative to traditional methods due to their low-cost, good miniaturization potential, as well as rapid and simple analysis. In spite of this, there are only few reports on the voltammetric determination of capsaicinoids. All these methods include extraction of capsaicin prior to the analysis, which enhances the costs of analysis and is time consuming. Here we will show that the voltammetry of immobilized microparticles can be used as a powerful technique for the direct determination of pungency in solid samples of hot peppers. The electrochemical behaviour of capsaicin on a paraffin-impregnated graphite electrode (PIGE) was investigated using square- wave (SWV) and cyclic voltammetry (CV) in a wide range of pHs and potential scan rates. The results revealed that the oxidation of capsaicin is an irreversible, pH dependent process, and involves the oxidation of the hydroxyl group in benzene ring. A redox mechanism for capsaicin oxidation has been proposed. Analysis of microparticles of dry ground pepper samples immobilized on the surface of PIGE was performed using SWV under optimal experimental condition: pH 11, ESW = 50 mV, f = 150 Hz, dE = 2 mV. The presence of capsaicin in samples was registered with good precision and sensitivity. The proposed methodology exploits the current intensity of capsaicinoids in pepper samples in order to classify samples according to their pungency. A strong positive correlation was observed between the measured peak currents for capsaicinoids in pepper samples and the average of Scoville heat units reported in the literature (R = 91.3 %, see Fig.2.).

voltammetry of immobilized particles ; square-vawe voltammetry ; capsaicin ; hot pepper ; pungency

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