食用油の水素添加に関する研究 (第1報)

水素添加オリブ油のグリセリド組成

抄録

Physical and chemical properties of hydrogenated oils produced at equivalent levels of hydrogenation of a fatty oil are affected to a signficant extent by changes in operating variables in hydrogenation. Although the fatty acid composition of hydrogenated oil may be the primary factor which influences physical properties such as melting behaviours and consistency, the glyceride composition is more closely and directly correlated with these physical properties. Effects of the operating variables upon the fatty acid composition of hydrogenated oil have been dealt with in a number of reports, but their effects upon the glyceride composition are not yet well understood.
In this paper, two hydrogenation runs of an olive oil (I.V. 87.5) were carried out with 0.15% of a commercial nickel catalyst under different conditions, one under relatively selective (180°C, 1.0kg/cm², 200rpm) and the other under relatively non-selective (150°C, 3.0kg/cm², 500rpm) conditions. The hydrogenation was continued until the iodine value has fallen to about 62. Four samples of hydrogenated oils were taken at different stages of hydrogenation, the iodine values of the corresponding samples being approximately same for both runs. Each sample was analyzed for its softening point, S.F.I., trans'is-omen (%) and fatty acid composition. Further, each of the hydrogenated samples and the original oil was separated by argentation-TLC into five fractions. From the yield and fatty acid composition of each fraction, the proportions of four glyceride types, i.e., GS 3, GS 2 U, GSU 2, and GU 3 were calculated.
Results of the experiments indicate that the non-selective hydrogenation favors the formation of high melting glycerides of the GS 3 type at equivalent levels of saturated acid content and accordingly gives S.F.I.-curves with a relatively gentle slope. It is postulated that in the selective hydrogenation the adsorption and desorption of glyceride molecules on the catalyst surface take place very frequently and the more unsaturated glyceride molecules are preferentially hydrogenated as compared to the less unsaturated glyceride molecules, whereas in the non-selective hydrogenation the double bonds remaining in the molecules once adsorbed on the catalyst surface are likely to be hydrogenated more or less preferentially as compared to the unsaturated fatty acid groups of other glyceride molecules.