DETECTION OF SOYBEAN ANTIGENICITY AND REDUCTION BY TWIN-SCREW EXTRUSION

Antiserum toward soybean meal was prepared by feeding a soybean meal diet containing large amounts of antigens to calves. The antiserum was used to develop a sensitive detection method for soybean meal antigens by competitive inhibition enzyme-linked immunosorbent assay. With this method, the effectiveness of twin screw extrusion cooking in reducing antigenicity in soybean meal was examined. Antigenicity was reduced to 0.1% of the original activity by extrusion cooking with screws containing kneading-disc elements and die-end temperatures exceeding 66 degrees C. Electrophoretic analysis of the cooked meal indicated that the reduction in antigenicity was due to degradation of protein structures, particularly those with molecular weights exceeding 40 kDa.