A versatile apparatus for the bench scale bleaching and deodorsation of vegetable oils

Abstract

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.

Keywords

• hexanal
• alkyl hydroperoxides
• heterolytic cleavage
• rapeseed oil
• bleaching