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A versatile isothermal glass apparatus provided with sintered glass on the bottom was designed for the bench scale adsorptive bleaching and deodorisation of vegetable oils. The stream of argon bubbles agitated the sample in both cases and protected the vegetable oil effectively against undesirable autoxidation and photooxygenation changes. However, a variable concentration of hexanal (27-30 μmol/kg) was always present in half-refined oils due to the heterolytic fragmentation of alkyl hydroperoxides. The colour on the Lovibond scale and the content of phosphorus (< 5 mg/kg) were efficiently decreased during the laboratory bleaching of rapeseed oil. It was found out that the adapted glass apparatus connected with a vacuum pump (1 hPa, a stream of argon gas instead of stripping steam) was able to reduce the content of carbonyl compounds below detectable concentration at 220-240°C. Furthermore, the extent of minor geometrical and positional isomerisation reactions was negligible (0.035-0.130 wt%). The results of the bench scale bleaching and deodorisation experiments were completely comparable with the industrial equipment under reduced pressure of the air. [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]