GB635571A - A process for refining vegetable and animal oils - Google Patents

Abstract

In the continuous method of refining vegetable and animal oils in two stages to remove free fatty acids, slime and colour substances, by the addition of neutralizing agent followed by centrifuging in each stage, the neutralizing agent is added in the first stage in smaller quantity than necessary for complete neutralization of the free fatty acids and in the second stage in excess of the amount necessary for complete neutralization of the free fatty acids, a soap almost free of fatty oil, slime- and colour-substances being obtained at the first stage and a soap mixed with the colloidal slime- and colour-substances being obtained at the second stage. Ordinary caustic soda lye is used and the invention is particularly exemplified with peanut oil, an oil of high fatty acid content. In either stage the oil may be preheated to such a high temperature that the formation of emulsion is prevented during the addition of the lye; alternatively the lye may be added to cold oil, the mixture then being heated to a sufficiently high temperature to break the emulsion. The latter effect may be facilitated by the addition of an emulsion-breaking electrolyte, such as common salt solution, before, during or after the heating. The lyes in the first stage are preferably of low concentrations as these are less adsorbent for slime- and colour-substances. The oil and soap at the neutralization point in each stage may be heated to a temperature higher than required for breaking the emulsions, the heating being preferably very rapid.