Abstract
In this study, 27 market and edible cold-pressed oils from 10 different oilseeds were analysed. Oxidative stability and the chemical composition of oils were evaluated. The oils were investigated for their primary quality, fatty acid composition, total phenolic content and antioxidant activity. Rancimat and pressure differential scanning calorimetry (PDSC) were used to assess oils oxidative stability. Principal component analysis (PCA) was conducted to determinate impact of selected chemical characteristics on tested oils’ oxidative stability in accelerated modes. PCA indicated that none of the chemical compounds correlated strongly with the oils’ oxidative stability determined by the Rancimat method. Correlation coefficients describing the impact of different chemical compounds on induction time determined using the Rancimat method were between r = −0.54 (C18:3) to r = 0.62 (chlorophyll pigments). Oxidative stability of oils determined using the Rancimat and pressure differential scanning calorimetry (PDSC) were characterised by low correlation (r = 0.66). According to the statistical analyses, oils were divided into four groups, which depend on the method of oxidative stability evaluation did not differ.
Highlights
Oxidative stability is one of the most important parameters used to assess oil quality, determining its resistance to the oxidation process
Analysed oils peroxide value was higher than panisidine value, which is typical for cold-pressed oils
The results of this study showed that both accelerated methods, the Rancimat and pressure differential scanning calorimetry, used to assess oxidation stability of cold-pressed oils from different oilseeds, were not highly correlated (r = 0.66)
Summary
Oxidative stability is one of the most important parameters used to assess oil quality, determining its resistance to the oxidation process. Its stability depends on the fatty acids composition and on the content of antioxidants, primary and secondary oxidation products, metals and other contaminants which might accelerate or inhibit oxidation process (Choe and Min 2006; Górnaś et al 2014; Szterk et al 2010). Shelf-life test involves placing oil samples on shelves and evaluating its basic quality features at regular time intervals (Farhoosh 2007). Due to the long duration of the test (several months) and the need to apply chemical reagents currently, to determinate oil oxidative stability, accelerated methods are mainly used. The Rancimat test is a popularly used accelerated oxidative stability evaluation method, it allows for a faster determination of the stability time by submitting the oil sample to a high temperature and constant airflow. Water conductivity is dependent on volatile compounds formed from the decomposition of unstable peroxides produced during the first step of oxidation (Raczyk et al 2016; Shahidi and Zhong 2005)
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