Trypsin inhibitor is one of the most important antinutritional factors in legumes. It decreases the utilisation of proteins and therefore reduces the utility of grain legumes for human and animal nutrition. Heat processing of soybean has proved to be an effective method for eliminating, or at least considerably reducing, the activity of antinutritional factors. This paper deals with the effect of instantaneous controlled pressure drop (Detente Instantanee Controlee or DIC) on soybean trypsin inhibitors. Trypsin inhibitor activity decreased by 94% after one minute of DIC treatment and by 99% after a six minute treatment, demonstrating the efficiency of DIC as a new process for soybean treatment. (c) 2006 Elsevier Ltd. All rights reserved.