A comparison of the stability of oils from Brazil nut, para rubber and passion fruit seeds

Abstract

The oxidation at 46 C of oils from Brazil nut, Bertholletia excelsa H.B.K.—Lecythidaceae (BNO), and from seeds of Para rubber, Hevea brasiliensis—Euphorbiaceae (PRO), and passion fruit, Passiflora edulis—f. flavicarpa—Passifloraceae (PFO), was followed over 115 days through the measurement of peroxide, acidity values, refractive indices, combustion energies and infrared (IR) spectra. The addition of 3 ppm Cu2+ to PFO oil shortened the induction period by 12%. The oxidation of BNO and PRO exhibited first-order kinetics in the production of hydroperoxide (RO2 H), up to the maximum values of the concentration of RO2 H. On the other hand, the oxidation of PFO and PFO+Cu2+ displayed first-order kinetics at higher concentrations of RO2 H and possibly half-order kinetics at low hydroperoxide concentrations in the first 15 days. Therefore, the 3 oils studied and PFO+Cu2+ did not show the same stability pattern over the 115 days of the experiment. The application of kinetic data, a side from the other parameters, allows the definition of 2 different stability patterns. From 0–15 days the oxidation rates led to the following order of stability: PFO+Cu2+<PFO<BNO<PRO. From the 15th day to the end of the period corresponding to the maximum concentration of RO2 H, the rate constants led to the pattern: PFO+Cu2+<BNO<PFO<PRO. Considering the whole period of the experiment, the changes in viscosity and the values of the induction periods point toward the first-mentioned stability pattern, demonstrating that without kinetic data these 2 parameters are insufficient to determine such patterns. © 1984, American Oil Chemists’ Society. All rights reserved.