AbstractA series of pilot plant batches of castor meal have been prepared using steam as the deactivating medium. Treatments consisted of 12 combinations of 10, 20, 40 and 80 psig steam pressure for 10, 30 and 60 min each. A multiple regression equation derived from the above data relates the guinea pig response to the process variables. This equation is also presented as a two‐dimensional surface contour. The antigenicity levels of untreated castor meals were found to be significantly different. This difference was not retained after treatment. Because of the uncertainty of the antigenicity of the pomace before treatment, an alcohol extract from castor beans (CBWU) has been adopted as a standard for potency evaluations. Amino acid analyses were performed on selected treatments. Considerable antigen deactivation has been achieved using mild steam treatments, e.g., 10 psig for 60 min. This process has a mild effect upon the essential amino acid, lysine.