The phosphorus content of refined soybean oil as a criterion of quality

Summary Restricted tests in pilot‐plant equipment have indicated that, starting with good quality crude soy‐bean oil, the phosphorus level of the deodorized oil is closely associated with its color and oxidative stability but that the refined or bleached color is not a good criterion for predicting the quality of the finished oil. Phosphorus is removed by water in the presence of adequate concentrations of alkali, and optimum oil quality is achieved at phosphorus levels in the deodorized oil of no less than about 2 and no greater than about 20 p.p.m. Over‐refining to a lower phosphorus content, by the use of too great an excess of caustic (and therefore of water) was harmful to oxidative stability in every instance and generally increased the color of the deodorized oil. The ash analysis of the deodorized oil is a fair indication of its residual phosphorus content at levels above 20 p.p.m.