Effects of a membrane-based soft purification process on olive oil quality

Because of the high temperatures applied in classical refining processes, many quantitative and qualitative changes occur in the chemical compositions of oils. This causes refined olive oil to lose many of its organoleptic and nutritional properties. Research has been carried out to ascertain the influence of a soft purification process, based on oil conditioning, to form micronic aggregates which were subsequently removed by a microfiltration operation. The quasi total acidity and the resulting soaps were removed in a single microfiltration step. The deacidified and filtered oils showed similar peroxide values and the variation of the specific extinction around 270 nm (ΔK) was slightly improved. The process lowered the monoglyceride contents up to 78% while the diglyceride contents were just slightly decreased. The various sterol components were also lowered (in the range 36–50%) upon treatment. Phenolics were the most affected components; reductions reached 93%. The partitioning of such components between the bulk triglyceridic medium and the aggregate phase are considered with regard to their properties. Despite the low operating temperature, the sensory evaluation of the deacidified and filtered oils still showed poor organoleptic characteristics.