A method for preserving cooking oil comprises contacting the oil with oil- permeable cementitious material in the form of either stand-alone blocks, pellets, granules, or balls and which has been hydraulically hardened from a paste comprising (a) >； 50 wt% of (i) white OPC clinker, (ii) white OPC or (iii) a mixture of white OPC clinker and white OPC, and (b) optionally further ingredients selected from silica, titama, lime, calcium sulphate, hydrated alumina, natural feldspars, diatomaceous earth, Na and Ca forms of natural and synthetic zeolites, clays, pillared clays, activated clays/earths, silicate minerals selected from calcium silicate, magnesium silicate, aluminium silicate, agalmatolite, amphiboles, attapulgite, granite porphyry, kaolinite, porphyry, rhyolite, talc and wollastonite, wherein the porosity of the cementious material is 30-55%. The treatment of the cooking oil takes place in a location separate from the frying chamber.
