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Here, we present the effect of rapeseed microstructure on the extraction mechanism. 'Solution and diffusion' extraction had to be considered to deepen the understanding of the process. Transmitted light microscopy images of the ultramicrotome-cut casting sections proved the presence of 'conductive' capillary system with radius R from 8 to 25 μm. The rate of 'solution extraction' was controlled by capillary flow through 'conductive' voids. It was described by derived and extended Hagen-Poiseuille equation. The rate of solvent extraction of soybeans was described by negative power function, whereas rapeseed extraction was defined by complex nonlinear curve-fitting model. Specific surface area of large (1.3 ± 0.1 m g) and small (1.5 ± 0.1 m g) fraction of rapeseed extraction meal particles did not differ significantly, contrary to flaked soybeans. This is the novel finding. Significant differences could be explained by vegetable seed histology context (seed and cell size, sorption abilities). 'Diffusion extraction' was rate determining at the flat part of the time-dependent extraction curve. Isolated fraction of free fatty acids originated from simultaneous lipolysis of acylglycerol species and hydrolysis of glycerophospholipids and glyceroglycolipids. Decreasing quality of last fractions increased refining loss and material costs. Compounds such as waxes (6.89-10.40 wt%), complex glycerolipids (14.83-15.26 wt%), and free fatty acids (2.26-2.45 wt%) had to be removed by edible oil refining. [ABSTRACT FROM AUTHOR]

To improve oil yield at the final stage of process, relation among solvent extraction mechanism and the removal of homo- and heterolipid classes with different acyl chain domains was studied. Selected technological parameter was decreasing quality of crude oil in the last successively extracted fractions. The composition of fatty acids, originally linked as lipid building-blocks, indicated no differences up to 94 wt% of hexane extractable oil from the rapeseed material. During the same time interval, it was released 95.8 cumulative wt% of oleic acid and only 76.9 cumulative wt% of ( Z)-11-octadecenoic (asclepic, cis-vaccenic) acid. Steep decrease of oleic acid content was correlated with the down-trend of total monounsaturated fatty acid concentrations in the simple glycerolipid fractions (from 57.0 -59.0 to 26.7 wt%) and free fatty acid fractions (from 59.0-60.0 to 40.1 wt%). On the other hand, we have observed 7.14-fold increase of asclepic acid concentration derived from the simple glycerolipids (mono-, di- and triacylglycerols), wax and sterol esters. The increment of asclepic acid was 4.78-fold in the fraction of the complex glycerolipids and acylate steryl glycosides. Lipidomic and proteomic analyses of isolated oil bodies, rapeseed hull and dehulled seeds proved an origin of ( Z)-11-octadecenoic acid. Furthermore, we determined similar fatty acid composition of lipid fractions derived from pure oil bodies and from dehulled seeds. In both cases, the low content of total asclepic acid: 3.13-3.15 wt% in aleurone cells was observed. Low amount of ( Z)-11-octadecenoic acid is novel finding, which indicated that ( Z)-11-octadecenoic acid originated from seed coat species that are less accessible to the hexane. It was confirmed that the main portion of asclepic acid moieties were derived from wax and sterol esters, triacylglycerols and heterolipids originally present in rapeseed coat (epidermal layer, testa and aleurone layer). Therefore, increasing amounts of asclepic acid and its precursor, palmitoleic acid, released from seed coats was significant indicator of solvent extraction process efficiency. [ABSTRACT FROM AUTHOR]

Conditions of deodorization/physical refining of sunflower oil were simulated by high temperature heating in laboratory at 240, 250, and 260 °C. Oxygen atmosphere was excluded by argon atmosphere. Influence of temperature, initial oxidation of incoming oil (peroxide value 2-30 mmol ½ O/kg) on geometrical, positional isomerization, and polymerization was measured. The level of initial oxidation of the oil has a significant influence on rate of isomerization, polymerization, and duration of induction period of polymerization reactions. Induction period of polymerization is dependent linearly on temperature at constant hydroperoxide content and is extended with decreasing temperature and lower peroxide value of oil. Significant conjugation took place with geometrical isomerization and resulted in all- trans diene formation. All- trans dienes are incoming reactants for polymerization according to the Diels-Alder mechanism. Suggested 'propagation' phase of polymerization took place later. Induction period was observed only in the case of polymerization reactions of triacylglycerols. This is the confirmation of the hypothesis that the cis/ trans isomerization, positional isomerization, and polymerization are consecutive reactions in ascending order. Identification of molecular peaks and confirmation of fragments were possible by connecting HPSEC with APCI-MS. Dimers of triacylglycerols (TAG) dominated in studied system. Remaining compounds may have been formed from di-, monoacylglycerols, and other minor constituents of sunflower oil. [ABSTRACT FROM AUTHOR]