Utilization of spent bleaching earth from vegetable oil processing

Introduction. The tests of Bulgarian bentonite, which is bleaching agent for vegetable oils, were conducted in industrial environments. The purpose is the compliance of standards to colouration vegetable oils. Materials and methods. Sunflower oil which was prepared by hot pressing method. The colouration was determined by spectrophotometric methods. Colour number, refraction coefficient, acidity, peroxide number and phospholipid determined by standard methods. Results and discussion. The results of the research carried out under industrial conditions provide the basis for the following main conclusions. A decrease in the carotenoids in bleached oils in comparison with unbleached oils, estimated according to their optical density was established by the spectra in the visible region at lambda from 400 to 700 nm. During oil bleaching, a process of positional isomerisation and the formation of dienes at 235 nm and trienes at 258, 268 and 278 nm occurred with regard to the unsaturated olefins in the oil triglycerides. The enrichment of the grist with 5, 10 and 15% of SBE did not increase the moisture content because the bleaching process was carried out at 105-110 degrees C and 17 mm HgS residual pressure. The increasing in the total oil and mineral (ash) content depended on the percentage of grist enrichment. During the storage of the enriched grist, their acid and peroxide values increased slightly compared to the initial grist. It is preferable to apply 10% addition of spent bleaching earth to enrich grist or feed blends with differentiated function.