A method for producing a monounsaturated cooking oil from beef tallow has been investigated. Immobilised lipases were used to interesterify tallow during fractional crystallisation from melted tallow, both with and without hexane present. Significant increases in the unsaturated fatty acid content of the liquid fractions were achieved by the use of lipases. The water content of the enzyme beads appeared to have a large effect on reaction rates and free fatty acid formation. The presence of hexane greatly improved the efficiency of the reaction by improving the efficiency of crystal filtration.