Kinetics of commercial olive oil oxidation: Dynamic differential scanning calorimetry and Rancimat studies

Abstract

Four samples of olive oil were oxidized under polythermal (dynamic) conditions in the cell of a normalpressure differential scanning calorimeter (DSC) and in the Metrohm Rancimat apparatus. The DSC experiments were carried out in an oxygen flow atmosphere using different linearly programmed heating rates in the range of 4-20 7C/min. Through DSC exotherms, the extrapolated onset temperatures were determined and used for the assessment of the thermal-oxidative stabilities of the samples. Using the Ozawa-Flynn-Wall method and the Arrhenius equation, the activation energies (E a ), pre-exponential factors (Z) and reaction rate constants (k) for oil oxidation under DSC conditions were calculated. The Rancimat measurements of oxidation induction times were carried out under isothermal conditions in an air atmosphere at temperatures from 100 to 140 7C with intervals of 10 7C. Using the Arrhenius-type correlation between the inverse of the induction times and the absolute temperature of the measurements, E a , Z, and k for oil oxidation under Rancimat conditions were calculated. The primary kinetic parameters derived from both methods were qualitatively consistent and they help to evaluate the oxidative stabilities of oils at increased temperatures.

Oxidative stability of camelina (Camelina sativa L.) oil using pressure differential scanning calorimetry and Rancimat method

“…Determining parameters of oil oxidation kinetics allows us to better assess their oxidation stability, suitability for processing and resistance to high temperatures during processing and storage [16,17,20,36]. Oxidation times determined for Rancimat (s on ) and PDSC (s max ) techniques presented in Table 2 enabled to prepare the graphical dependences between logarithm of s max and s on and temperature (Figs.…”

“…Metrohm Rancimat (Europe) test and OSI-oxidative stability index (USA)-are commonly applied for analysis of edible oils [16,17], however, they cannot always be successfully used to analyze cold-pressed oils, despite being useful in assessing refined oils. Studies on oil oxidation using the DSC technique, under both isothermal (constant operating temperature) and dynamic conditions (linear temperature growth), have been carried out so far [17][18][19][20]. Nevertheless, studies were mostly conducted on refined oils [17,20,21].…”

“…Studies on oil oxidation using the DSC technique, under both isothermal (constant operating temperature) and dynamic conditions (linear temperature growth), have been carried out so far [17][18][19][20]. Nevertheless, studies were mostly conducted on refined oils [17,20,21]. Parameters of coldpressed oils-relatively high non-glycerol content, very high influence of the raw material on final product quality and pressing parameters on the oil content-make the selection of the appropriate method and conditions of the analysis arduous and difficult.…”

Use of GC and PDSC methods to characterize human milk fat substitutes obtained from lard and milk thistle oil mixtures

“…In order to maintain a healthy product, it is important that lipids are oxidatively stable [12]. Differential scanning calorimetry (DSC) is one of the most popular methods for the appraisal of the oxidative stability of oils and fats [16]. It is based on measuring of the induction times of oils oxidation.…”

Application of the calorimetric and spectroscopic methods in analytical evaluation of the human milk fat substitutes

“…Classical methods are based on ''wet chemistry'' [19]. Nowadays, instrumental methods are commonly used as they are faster, more precise, have wider scope of detection, and are more objective [20]. Differential scanning calorimetry (DSC) is a nonchemical method to determine fat quality parameters [17,[21][22][23].…”