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Chemical characteristics and thermal oxidative stability of novel cold-pressed oil blends: GC, LF NMR, and DSC studies
Plant oils contain a high content of unsaturated fatty acids. Studies of food products have revealed a considerable disproportion in the ratio of ω6 to ω3. This article presents information on the healthful qualities of eight new oil blends that contain a beneficial proportion of ω6 to ω3 fatty acids (5:1), as well as their degradation during heating at 170 and 200 °C. The fatty acid profile was analyzed by gas chromatography (GC), content of polar compounds and polymers of triacylglycerols by liquid chromatography (LC), water content was measured by the Karl Fischer method, and oxidative stability was measured by differential scanning calorimetry (DSC) and low-field nuclear magnetic resonance (LF NMR) methods. The results showed that during heating, the polar fraction content increased in samples heated at both analyzed temperatures compared to unheated oils. This was mainly due to the polymerization of triacylglycerols forming dimers. In some samples that were heated, particularly those heated to 200 °C, trimers were detected, however, even with the changes that were observed, the polar fraction content of the blends did not go beyond the limit. Despite the high content of unsaturated fatty acids, the analyzed blends of oils are characterized by high oxidative stability, confirmed by thermoanalytical and nuclear magnetic resonance methods. The high nutritional value as well as the oxidative stability of the developed oil blends allow them to be used in the production of food, in particular products that ensure an adequate supply of ω3 fatty acids.
Characteristics of Langmuir monomolecular monolayers formed by the novel oil blends
Abstract The aim of this work was to assess the physical properties of Langmuir monolayers of three new oil blends “RBWg” (obtained by mixing rapeseed oil, black cumin oil, and wheat germ oil), “REp” (rapeseed oil and evening primrose oil), and “CRb” (camelina oil and rice bran oil), as well as to characterize the molecular dynamics of their protons using low-field nuclear magnetic resonance (LF NMR) method. The studied blends are rich in oleic acid (C18:1), linolenic acid (C18:2), and α-linolenic acid (18:3). The chromatographically determined ratio of n6 to n3 fatty acids was found to be in the range of 5.18–5.27. The appropriate n6/n3 fatty acid ratio was also confirmed by FT-IR analysis. The spin–lattice relaxation rate (R 1) and spin–spin relaxation time (R 2) measured by LF NMR method were similar for the RBWg and REp blends but different from the third oil blend (CRb), which indicates lower proton mobility in CRb. The observed changes in the properties of monolayers of oil blends suggest that the refined rice bran oil in the CRb blend also significantly changes the viscoelastic properties of this blend. The results obtained in this study provide a theoretical basis for the development of a well-balanced approach to using oils in food production technology.