GB865807A - Improvements in or relating to the treatment of edible oils - Google Patents

Abstract

Edible glyceride oils are refined by a process in which a solution of the oil in a nonpolar solvent, such as light petroleum, hexane, or cyclohexane, is brought into contact with activated alumina, after which the solvent is removed, the residual oil subjected to steam deodorization, and an antioxidant added. The alumina is suitably obtained by activating gibbsite or bayerite by roasting at 350-900 DEG C. for 5 hours or more, and the solution of oil, usually a 5-50% w/v solution, is passed down a column of the alumina amounting to 5-500% by weight of the oil. If preferred, however, the alumina may merely be agitated with the oil. The column is then generally washed with pure solvent to recover occluded oil and the eluates combined, after which the solvent is removed by distillation and the remaining oil steam-deodorized at 140-180 DEG C. at reduced pressure. Suitable antioxidants which may then be added are the alkyl esters of hydroxybenzoic acids, especially propyl, octyl, and dodecyl gallates, tert. alkyl substitution product of hydroxyalkoxybenzenes, especially 2- or 3- tert. butyl-4-hydroxyanisole, and trialkyl substitution products of phenol, for example 2:6-ditert. butyl-4-methylphenol. The antioxidant may be added to the main bulk of the oil, generally in amounts of 0.001-0.1%, usually as a solution in either a small quantity of the oil or in propylene glycol. It is also preferred that an equal amount of citric acid be added. The oils to be treated should desirably have been alkali refined but not bleached, and include cottonseed, olive, groundnut, sesame, sunflower, safflower, soyabean, and rapeseed oils. According to the Provisional Specification, the antioxidant may be added before or during the deodorization step, and the antioxidant may be nordihydroguaiaretic acid.