Synthesis and properties of very high erucic acid oils

Abstract

Very high erucic acid oils have potential industrial uses and many different techniques are being studied to develop crops that could produce these oils. However, the physical properties of these potential oils have not been studied very thoroughly. This research was designed to first synthesize very high erucic acid oils and then to characterize their physical and chemical properties. A method was developed for the synthesis of trierucin by direct esterification of glycerol and erucic acid, without the use of a catalyst. The esterification reaction was conducted in a two-step heating process under 25 mm Hg vacuum. The two-step heating process included heating glycerol and erucic acid at 160±5°C for 4 hr followed by heating at 250±10°C for 8 hr. Purification of the esterified product was achieved by alkali refining followed by passing through an alumina column. Greater than 85% yield of pure triacylglycerols, containing ~90% erucic acid, was obtained through chemical synthesis by using a 5% molar excess of erucic acid in the reaction. The use of an initial low temperature (160±5°C) of reaction resulted in a light colored product with optimum yield of trierucin. Erucic acid oils containing 45 to 91% erucic acid content were prepared by interesterifying native HEAR oil and synthetic oil product. Chemical and physical properties of all these synthetic oils were then examined. Melting point, cloud point, pour point, titer, viscosity and heat capacity of all synthetic oils exhibited positive correlations with the erucic acid content, whereas saponification value, iodine value and refractive index showed negative correlations. Randomization of HEAR oil resulted in an increase in the melting point, cloud point and pour point. Very high erucic acid oils, having a low degree of unsaturation, will be able to withstand oxidation, and will remain stable during high temperature processing conditions. The increased viscosity of very high erucic acid oils will also add to the lubrication capability of these oils. The use of very high erucic acid oils would be limited by their melting point as they would be solid at room temperature. These synthetic oils could find use in lubrication and in high temperature applications and work to produce these oils through selective breeding of plants, or through chemical synthesis should continue.