The present work was designed to study the effect of different processing operations on the activity of trypsin inhibitor and chemical composition as well. Regarding potatoes some processing criteria were examined mainly: soaking, frying, frying after soaking, boiling and grilling. But as for wheat soaking, boiling, boiling after soaking, extraction, fermentation and baking were tasted. The obtained data showed the following, soaking only not effective on reduced trypsin inhibitor but boiling, frying, frying after soaking and grilling were more effective for reducing trypsin inhibitor on potatoes. For wheat, boiling after soaking was more effective than soaking or boiling only. The effect of extraction and fermentation on trypsin inhibitor activity was significant but baking was sufficient for reducing (TIA) so that, no TI was almost obtained in breads.