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°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.