Determination of hydroperoxides in oils and fats using kits

The primary products of lipid oxidation are peroxides, which are usually quantified using iodometric methods, although interferent action and difficulty in determining the titration end point can lead to imprecise results. PeroxySafe (TM) kits determine the peroxide value (PV) on the basis of ferrous oxidation in the presence of xylenol orange in an acidic medium. They provide a fast and simple alternative requiring minimal sample sizes and generating few residues. The present study, correlating statistically the results of these kits with the official iodometric method (AOCS method Cd 8b-90) for the determination of PVs of refined vegetable oils, lard and hidrogenated fats, proved that they can be used satisfactorily. Larger differences were found for PVs of less than 2 meq kg(-1) owing to the relatively small titrant volume used in the official method. The low sensitivity of the official iodometric method was not compensated for by the use of a more dilute solution, although it was assumed that the use of a larger volume of titrant would lead to a smaller difference. The results obtained here revealed that the PVs had doubled, with the kits giving up to four times those obtained using the modification of the official method. (c) 2007 Society of Chemical Industry.8791659166