Easy and green method for the peroxide value determination in olive oil

Le résumé fourni par la source

The official method for the determination of the peroxide content in olive oil (PV) is based on iodometric titration, i.e. on the redox reaction between the oil hydroperoxides with potassium iodide; the latter, in an acidic environment, releases molecular iodine. The iodine released is complexed by starch which acts as an indicator. By quantifying the iodine liberated with sodium thiosulphate, the hydroperoxide concentration can be calculated. One of the well-known problems of this method is the co-presence of the interfering reaction due to the oxidation of iodide by oxygen present in solution, causing an overestimation of the PV. In addition, the accuracy of the method is influenced by a variety of experimental factors such as skill of operator, light, temperature, sodium thiosulfate decomposition. Furthermore, the iodine released in the organic phase can also react with unsaturated lipids and cause an underestimation of the concentration of peroxides. Finally, this method requires relatively long analysis times, large amounts of sample and organic solvents with a high environmental impact. Considering these disadvantages, a novel approach based on the spectrophotometric detection of triiodide was developed. Olive oil sample was added with 0.5 % HCl in ethanol, saturated KI solution and incubated. Then, the resulting solution was filtered and the I3- generated following the oxidation-reduction reaction between iodide and lipidic hydroperoxides was measured at 353 nm. A good linearity (with correlation coefficient (r) of 0.9997) of the calibration curve was obtained with purified olive oil spiked with tert-butylhydroperoxide at levels ranging from 1.0 to 10.0 meqO2/kg, with variation coefficients less than 5% (n = 3) and limit of detection and quantification of 0.3 and 0.9 meqO2/kg, respectively. Results obtained with the spectrophotometric method showed good correlation with those obtained with the official method with a r of 0.9819 confirming the reliability of the developed method.

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