Determination of Dimers and Polymers in Heated Fats and Oils by Sublimation
Abstract A sublimation procedure is described for separating dimers and polymers from oxidized or polymerized fats and oils. Under the described conditions, involving sublimation at 90°C and 0.02–0.05 mm Hg pressure, common fatty acid methyl esters standards yielded 99–2100% sublimate, methyl esters of commercial vegetable oils yielded 97.4-99.2% sublimate, heated cottonseed oils yielded 64–83% sublimate, a thermal dimer acid yielded 1.0% sublimate, and laboratory-prepared oxidative dimers and polymers yielded 7.5% sublimate. A comparison of the sublimation procedure with urea adduction gave good correlations with thermally oxidized oil samples; however, with fresh vegetable oil or with samples consisting of predominantly thermal or oxidative dimers, sublimation gave more accurate results than urea adduction.
