Abstract
Contents of cis- and trans-isomers in domestic margarine oils (“soft types 15” hard types 10) were determined by gas chromatographic (GLC), enzymatic and infrared spectrophotometric (IR) methods.
Results obtained were as follows:
1) Average contents of trans-C18: 1, cis, trans- and trans, trans-C18: 2 were 8.44, 1.29 and 0.18% in the soft type and 12.72, 1.45 and 0.75% in the hard type, respectively. It was noticed that the content of trans-isomers of C18: 2, was much lower than that of C18: 1, in all samples, moreover trans, trans-C18: 2 was not detected in 15 samples (soft: 12, hard: 3).
2) Average content of cis, cis-methylene interrupted polyunsaturated fatty acids determined by enzymatic method was 38.68% in the soft type and 20.39% in the hard type. In general, its content tended to slightly higher than that of cis, cis-C18: 2 determined by GLC method.
3) The difference between the total trans acids content determined by IR method and the total trans-isomers content of C18: 1 and C18: 2 determined by GLC method could not be regarded as significant. But the value by IR method can almost be regarded as trans-monoenoic acid content, because of much lower content of trans-isomers of dienoic acid than it in the margarine.
4) The percentage of trans-isomers to total C18: 2 among the soft type margarine tended to lower than that of hard type, especially in high linoleic type which contained more than 45% C18: 2 showing 1.4% value. It was also noticed that the percentage of trans-isomer to total C18: 1 in domestic margarines was 25.7%. This result indicates that the amount of trans-isomers of domestic margarine is lower than some foreign ones.
