FOOD. Science. Technology. Quality

Food. SCIENCE. Technology. Quality

Food. Science. TECHNOLOGY. Quality

Food. Science. Technology. QUALITY




Assessing the effect of pressing conditions in expeller press on quality and chemical composition of rapeseed oil


The objective of this study was to determine the effect of pressing conditions in an UNO expeller press (manufactured by a ‘Farmet’ company) on the quality and chemical composition of pressed rapeseed oil. The research material included 2 batches of industrial rapeseed from the harvest campaigns in 2010 and 2011. Oils were pressed from rapeseed in the expeller machine (a screw-type press) with 3 different nozzles, their diameters being 6, 8, and 10 mm. Also, one batch of seeds was additionally heated (150 °C, 1 h) prior to pressing. The content of water and fat in the seeds and in rapeseed cake were determined as was the content of contaminations in the seeds. The extraction efficiency was computed. In the oils determined were the degree of hydrolysis, the primary and secondary lipid oxidation degree (acid value, peroxide value, and anisidine value; Totox index was computed]. Moreover, the colour of oils was determined as were the content of pheophytin a, the composition of fatty acids, and the oxidative stability according to the Rancimat test (120 °C). It was found that with the use of the expeller press for cold pressing, and regardless of the nozzle used, it was possible to press oil under very mild conditions, at a temperature ranging from 38 to 42 °C, and no oxidative changes occurred in the fat as regards the content of primary and secondary products of fat oxidation; furthermore, no changes were produced in the composition of fatty acids and in oxidative stability of the oils pressed. However, the extraction efficiency was relatively low (40 – 50 %), and the residual fat content in the cake was high (20 – 27 %). Similar trends were found in the case of the two analyzed batches of rapeseed. The heating of seeds prior to pressing caused the extraction efficiency to significantly increase, and, simultaneously, the degree of hydrolysis of lipids and the content of pheophytin to slightly increase; the heating prior to pressing also caused the colour of the oil produced to darken.


cold pressing, expeller press, rapeseed oil, quality, stability, Rancimat test, composition of fatty acids