Optimisation of soya bean oil bleaching by ultrasonic processing and investigate the physico‐chemical properties of bleached soya bean oil

Abstract

Summary In this study, an ultrasonic bleaching method for soya bean oil under different conditions was optimised by monitoring the reduction of oil‐containing colourants. Ultrasonic power, clay content, temperature and time had a significant interaction effect on (P < 0.05) the reduction of oil pigments and colourants. Under optimised conditions, red and yellow colour indices in the ultrasound‐bleached soya bean oil reduced to 74.44% and 75.55%, and 54.18% and 58.85%, respectively, at amplitudes of 85% and 65%. Carotenoid and chlorophyll concentrations also reduced to 81.19% and 83.62%, and 94.66% and 95.26%, respectively, at 85% and 65% ultrasonic power. The overall contents of sterols and tocopherols decreased using ultrasonic bleaching process compared with the neutralised soya bean oil. Although the peroxide value (PV) of the soya bean oil after ultrasonic and control bleaching reduced, this index was higher in the ultrasonic bleached oil than the control one. The results showed that the ultrasonic bleaching process could be an alternative to the industrial bleaching method as it reduced clay usage, temperature and time of bleaching about 35%, 35% and 10%, respectively.

The Effect of Ultrasonic Waves in Bleaching of Olive and Sunflower Oils and Comparison with Conventional Bleaching

“…Their findings proved that the fatty acid composition of the vegetable oils does not change after ultrasonic treatment (Chemat et al 2004). Also, Abedi et al (2015) showed that the ultrasonic process did not alter the fatty acid profile and no significant difference between the bleached oil under ultrasonic and control processes were observed. Therefore, it could be concluded that ultrasonic waves will have no destructive effects on the fatty acid compositions if the applied condition of sonication was controlled.…”

“…It can be concluded that the ultrasonic methods had been completely effective in removal of the red and yellow colors in the examined oil samples and its impact is more significant in olive oil than in sunflower oil. According to the American trading rules, maximum 2.5 red and 25 yellow units are the acceptable colors units for the bleached oils (Rossell and Pritchard 1991;Abedi et al 2015).…”

“…In the chemical refining, the bleaching process is a complementary step after degumming and neutralization which more appropriately referred to as adsorption treatment (Erten 2004). In other words, oil bleaching is a process whereby the clay adsorbents are mixed with the oil under specified conditions in order to remove unwanted components such as pigments (Abedi et al 2015). The primary functions of the bleaching in combination with catalytic actions are destruction of peroxide and equilibrium adsorption, which consists of removing the peroxides and secondary oxidation products.…”

“…The primary functions of the bleaching in combination with catalytic actions are destruction of peroxide and equilibrium adsorption, which consists of removing the peroxides and secondary oxidation products. Due to possible defects caused by the presence of decomposed peroxides, volatile aldehydes and ketones are removed in further steps However, pigments and any residues of gums and soaps from refining can also be removed (Reddy et al 2001;Abedi et al 2015).…”

“…However, chemical refining processes usually consume 0.5-2% bleaching earth on the weight basis 2-4% also can be used to obtain the desired reduction of color (Valenzulela Diaz and Souza Santos 2001). As one of the highly remarked disadvantages, long time process should be applied for the separation of bleaching earth from oils due their fine size and compact structures; therefore, the duration of the filtration step will be increased, which could cause some damages in the quality of oil (Abedi et al 2015). Also consumption of high amounts of bleaching earth could be resulted to more oil losses (Hussin et al 2011).…”