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Evaluation of the Oxidative Stability of Cold‐Pressed Rapeseed Oil by Rancimat and Pressure Differential Scanning Calorimetry Measurements

Symoniuk, Edyta, Ratusz, Katarzyna, Krygier, Krzysztof
European journal of lipid science and technology 2019 v.121 no.2 pp. e1800017
antioxidant activity, differential scanning calorimetry, fatty acid composition, markets, monounsaturated fatty acids, oxidation, oxidative stability, peroxide value, pigments, polyphenols, polyunsaturated fatty acids, principal component analysis, rapeseed oil, temperature
Cold‐pressed market rapeseed oils are evaluated for oxidative stability using two accelerated methods: Rancimat and pressure differential scanning calorimetry. In the study, oils are also determined by their acid, peroxide and p‐anisidine values, fatty acid composition, antioxidants capacity, and phenolic compounds content. Obtained results of oxidative stability are correlated to determine the possibility of using interchangeably tested methods. To examine the impact of individual quality factors on oil oxidative stability, the principal components analysis is applied. Analyzed oils are characterized by good quality, having a typical fatty acid composition, and oxidative stability. Rapeseed oils induction time are determined by Rancimat measurement at 100 °C and pressure differential scanning calorimetry test at a temperature of 120 °C. The induction times obtained using these two methods are strongly correlated (r = 0.96). A high value of correlation coefficient might be caused by too little differentiation; thus the possibility of using these methods interchangeably may be applied only to results range between 12.96 and 14.03 h for a Rancimat method and 60.28–67.05 min for PDSC measurements. Principal components analysis shows that the greatest influence on rapeseed oil induction time in Rancimat, and PDSC methods have peroxide values (r = −0.73 and r = −0.80, respectively), Totox indicators (r = −0.67 and r = −0.75, respectively), and total polyphenols content (r = 0.67 and r = 0.78, respectively). There is no correlation between the monounsaturated fatty acid content and the antioxidant capacity. Moreover, the induction time is poorly correlated with saturated, polyunsaturated fatty acids, and pigments content. Practical Applications: The results show that Rancimat and pressure differential scanning calorimetry (PDSC) methods might be used interchangeably (r = 0.96) for assessing the oxidation stability of cold‐pressed rapeseed oil, for a given set of data. PDSC can be recommended as an appropriate objective method for evaluating the oxidative stability of cold‐pressed rapeseed oils. Results of the principal component analysis (PCA) proved that its primary oxidation state has a high influence on cold‐pressed rapeseed oil oxidative stability. Differences in rapeseed oil oxidation stability do not depend on its fatty acid composition. Market cold‐pressed rapeseed oils are evaluated for their chemical composition and oxidative stability using Rancimat and PDSC measurements. Based on the obtained results the correlation between oxidative stability determined by these two methods and the influence of the individual quality factors on oil oxidative stability is determined by applying the principal component analysis.