Plant Materials. The samples analyzed for phenolic composition included Neepawa wheat, Neepawa wheat flour, Harmon oats, yellow dent com, long grain brown rice, and Netted Gem potatoes.The seed samples were mature, sound, and, except for rice, had been harvested about 2 months previously.The cereals, after dehulling in the case of oats, were debranned by roller milling or pearling and ground into a fine flour. The potatoes were peeled, sliced, freeze-dried, and ground.

Fenton et al. (1980) reported that previous investigators had failed to consider cis and trans isomerization of phenolic compounds, interference by lipids, and formation of artifacts during extraction and separation procedures.The objective of this investigation was to develop a more rapid procedure for the accurate estimation of the free, esterified, and insoluble-bound phenolic acids. Although

No 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.

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.