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<p>The oxidative stabilities of avocado, macadamia, marula and moringa oils were determined at different temperatures using Rancimat analysis and also with pressure differential scanning calorimetry (PDSC) at different scan rates. The experimental data were regressed using the single-step kinetics approximation. The estimated activation energies and the characteristic time constants obtained by the two methods were found to differ. These differences were considered in the construction of an expression that links the Rancimat oxidation induction time (OIt = <i>t</i><sub><i>R</i></sub>) to the oxidation onset temperature (OOT = <i>T</i><sub>onset</sub>): <Equation ID="Equa"> <EquationSource Format="TEX">\(\ln {t_R} \approx A+\frac{B}{{{T_{iso}}}}+\frac{C}{{{T_{onset}}}} - \ln \beta\)</EquationSource> </Equation> Where <i>T</i><sub><i>iso</i></sub> is the temperature at which the Rancimat is operated, <i>β</i> is the temperature scan rate used in the PDSC run and A, B and C are oil-specific material constants. The Rancimat-measured OIt results indicated the following order of oil stability: Marula &gt; moringa &gt; macadamia &gt; avocado. However, PDSC results indicated that the macadamia oil was less stable than avocado oil. The PDSC tests returned OOT values in the range typically used for food frying, i.e. 160–190&#xa0;°C. Rancimat evaluations usually employ significantly lower test temperatures (below 140&#xa0;°C). The implication is that the OOT approach might provide a more realistic assessment of the oxidation susceptibility for certain oils intended for frying.</p>

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Oxidative stability of edible oils: linking rancimat to PDSC results

  • 期刊论文

  • 发表日期：

    2025年11月8日

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  • Ana-María Díaz-Díaz,
  • Jorge José López-Beceiro,
  • Ramón Pedro Artiaga Díaz,
  • Wilma Augustyn,
  • Isbe Van der Westhuizen,
  • Walter Wilhelm Focke

摘要

The oxidative stabilities of avocado, macadamia, marula and moringa oils were determined at different temperatures using Rancimat analysis and also with pressure differential scanning calorimetry (PDSC) at different scan rates. The experimental data were regressed using the single-step kinetics approximation. The estimated activation energies and the characteristic time constants obtained by the two methods were found to differ. These differences were considered in the construction of an expression that links the Rancimat oxidation induction time (OIt = tR) to the oxidation onset temperature (OOT = Tonset): \(\ln {t_R} \approx A+\frac{B}{{{T_{iso}}}}+\frac{C}{{{T_{onset}}}} - \ln \beta\) Where Tiso is the temperature at which the Rancimat is operated, β is the temperature scan rate used in the PDSC run and A, B and C are oil-specific material constants. The Rancimat-measured OIt results indicated the following order of oil stability: Marula > moringa > macadamia > avocado. However, PDSC results indicated that the macadamia oil was less stable than avocado oil. The PDSC tests returned OOT values in the range typically used for food frying, i.e. 160–190 °C. Rancimat evaluations usually employ significantly lower test temperatures (below 140 °C). The implication is that the OOT approach might provide a more realistic assessment of the oxidation susceptibility for certain oils intended for frying.