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Oxidative stability and the chemical composition of market cold-pressed linseed oil

Research paper by Edyta Symoniuk, Katarzyna Ratusz, Krzysztof Krygier

Indexed on: 24 Oct '17Published on: 08 Aug '17Published in: European Journal of Lipid Science and Technology



Abstract

Oxidative stability and minor components of market linseed oils were evaluated. The oils were investigated for their primary and secondary oxidation products, fatty acid composition and pigment content, and samples were also examined for their scavenging of 1, 1- diphenyl-2-picrylhydrazyl (DPPH) and total phenolic content. Rancimat and pressure differential scanning calorimetry were used to assess oxidative stability. The analysed oils were of good quality, meeting the requirements of the Codex Alimentarius standard. Linseed oils were characterised by 45–65% content of α-linolenic acid. The TEAC equivalent of linseed oils ranged from 1.25 to 1.42 mM of Trolox kg−1 oil, and FAE ranged from 60.25 to 115.12 mg of ferulic acid 100 g−1 oil. The correlation between linseed oil oxidative stability as measured by the Rancimat and PDSC methods was low (r = 0.55). Based on the obtained results of oxidative stability and the content of chemical compounds, principal components analysis was conducted. PCA indicated that none of the chemical compounds correlated strongly with the oxidative stability of linseed oils as determined by the Rancimat method. However, in the case of the PDSC method, the content of primary and secondary products of oxidation had the strongest impact on the oxidative stability of linseed oils. The correlation coefficients describing the impact of different chemical compounds on induction time using the Rancimat and PDSC tests were between −0.43 to 0.45 and −0.82 to 0.72, respectively.Practical applications: The results show that linseed oils available on the market were of differing but good quality. Results of oxidative stability tests demonstrate that Rancimat and pressure differential scanning calorimetry (PDSC) methods should not be used interchangeably for assessing linseed oil oxidative stability (r = 0.55). The initial degree of oxidation had the greatest impact on the oxidative stability of linseed oil, but none of the measured quality parameters showed a high correlation with the Rancimat induction time. Principal component analysis verified the designated correlations between induction times in the Rancimat and PDSC tests and quality features. PCA also confirmed differences between the examined linseed oils.Market linseed oils are examined to their oxidative stability using Rancimat and pressure differential scanning calorimetry, and their chemical composition. The influence of selected discriminants on the oxidative stability of linseed oil is determined.