Kinetics of geometrical isomerization of unsaturated FA in soybean oil |
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Authors: | Nadja Ger?ar Andrej ?midovnik |
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Affiliation: | (1) Laboratory of Food Chemistry, National Institute of Chemistry, Hajdrihova 19, S1-1000 Ljubljana, Slovenia |
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Abstract: | Laboratory treatment of soybean oil were carried out at the following conditions: atmospheric pressure in the presence of
air or nitrogen at different temperatures ranging from 160 to 250°C for 12 to 72 h. These conditions were used to study geometric
isomerization of cis,cis-linoleic and cis,cis,cis-linolenic acid in the presence or in the absence of oxidative degradation reactions. Based on these experiments, a model
of consecutive, parallel reactions was developed to describe the reaction steps occurring in the soybean oil during heating
at constant temperature. For both cis,cis-linoleic and cis,cis,cis-linolenic acid, the reaction of formation isomers followed a first-order reaction, and the rate constant of isomerization
varied according to the Arrhenius law. The isomerization rate constant for linoleic acid was 9.57×10−3±0.50 h−1 in the presence of oxygen and 7.39×10−3±0.39 h−1 in its absence, and the isomerization rate constant for linolenic acid was 1.18×10−1±0.10 h−1 in the presence of oxygen and 0.87×10−1±0.07 h−1 in its absence (all obtained at 250°C). |
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Keywords: | Isomerization kinetics linoleic acid linolenic acid modeling oxidation soybean oil |
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