Oil bleaching is a refining stage in which crude or neutralised vegetable oil is treated with bleaching earth or activated carbon to adsorb pigments, residual soaps and oxidation products, improving colour and stability before deodorisation.
In trade practice
Bleaching earth is mixed with the oil under vacuum and mild heat, then removed by pressure filtration; spent earth is a regulated waste stream that refiners must handle separately. QA teams assess the result by Lovibond colorimeter, comparing red and yellow units against the buyer’s specification. A common problem is over-bleaching, which can strip natural antioxidants and shorten shelf life. Buyers should request colour data alongside peroxide value to confirm the stage was carried out correctly.
In a specification
A refined oil specification typically states maximum Lovibond colour values, for example red and yellow units measured in a defined cell length, as the primary acceptance criterion for the bleaching outcome.