Effects of plant-scale alkali refining and physical refining on the quality of rapeseed oil
The physical refining of soybean oil was introduced as an energy saving and environmentally friendly procedure alternative to the traditional alkali refining, and the process was successfully applied to other vegetable oils. We had compared the two procedures in industrial refining under conditions, which enable a clear comparison. In nine plant-scale experiments, crude rapeseed oil, taken from the same tank of crude oil, was processed on the same day both by alkali refining and by physical refining. Quality changes (free fatty acids, peroxide value, conjugated fatty acids, polar lipids, minor constituents) were determined, and also their stability against oxidation (Rancimat and Schaal Oven Test), and the fatty acid composition. In refined oils, the sensory acceptabilities and the sensory profiles were assayed. Finally deodorized oils, produced by the two methods, did not appreciably differ in their sensory characteristics and chemical composition, excepting slightly higher concentration of isomeric polyunsaturated fatty acids in physically refined oils. During storage for one year in commercial packagings at 15 °C, oxidative and sensory changes were negligible.