Impurities in vegetable oil refining soapstock

Abstract

SummaryThe nature of the impurities in vegetable oil foots renders them resistant to treatment by acids as in normal acidulation. Strong caustic was found to attack the gums and make them at least partially soluble in a 5 to 10% aqueous caustic solution. At this concentration a soap phase of 45–60% TFA could be centrifugally separated, and the majority of the impurities or their degraded products were discharged in the lye. The ratio of Oxidized Acids and Insoluble Impurities to the TFA was much lower in the soap than in the raw soapstock; the Oxidized Acids/Black Acids ratio could generally be reduced to 5% or less. This reduction in impurities was found to improve laboratory still yields markedly without the necessity of Twitchell‐ or pressure‐ splitting the black acids from treated stocks. Distillate yields of 86–89% were obtained from treated stocks, compared to 69–70% from untreated stocks.