REGENERATION OF OILS USED FOR DEEP FRYING - A COMPARISON OF ACTIVE-FILTER AIDS

A number of products are promoted for the purpose of regenerating used frying oils. These materials are referred to as ''active'' filter aid s. They are purported to adsorb polar compounds, which are the product s of oil degradation, and to retain them for removal by filtration. To evaluate some of these materials, portions of a used oil were treated with each of several ''active'' filter aids and filtered in a commerc ial-type recirculating oil filter. The triglycerides and any adsorbed compounds were extracted from the filter cake with a series of increas ingly polar organic solvents. The composition of each of the filter ca kes was quantitatively determined. The materials tested in this study were diatomaceous earth, acid-activated bleaching earth, activated alu minas, silica, carbon and synthetic magnesium silicate. Significant di fferences in the adsorbent characteristics of the materials were found . Adsorption of polar oil degradation compounds ranged from 2 mg of po lar compounds per gram of diatomaceous earth to about 200 mg/g magnesi um silicate.