Improvement of Keeping Quality of Butteroil by Selective Trace-Hydrogenation and Winterization1,2

Abstract

The effect of very slight hydrogenation on the keeping quality of butteroil has been studied. Under selective conditions of low pressure, low catalyst concentration, and at 140C, such trace-hydrogenation proceeded at a controllable and moderately rapid rate. Samples of deodorized hydrogenated butteroil having iodine values reduced by 1.4, 2.5, 3.5, and 6.0 units were compared against deodorized unhydrogenated butteroil after storing at 60C. Both organoleptic evaluation and peroxide number determinations showed hydrogenated samples to have much improved keeping quality. A significant improvement was achieved by reducing the iodine value by only 1.4 units, whereas a reduction greater than 2.5 units did not offer any further improvement. Hence, it has been shown that butteroil of greatly improved keeping quality may be otained by very slight hydrogeneration with only a little loss of unsaturation. The level of unsaturation may be restored conveniently by winterization from a solvent such as n-hexane.Analysis of fatty acid composition of the hydrogenated and unhydrogenated butter oils indicated that the improvement of keeping quality by selective trace-hydrogenation is due to the diminishing of the highly unsaturated fatty acids such as linolenic and arachidonic acids.