[Ureasic activity in soy products. Proposal of a new method]

The evaluation of residual ureasic activity in soy products is usually employed as an indicator of the efficiency of the inhibition treatments. The purpose of this study is to compare the AACC method (22-90), based on differences of pH, with an assay where ureasic activity is measured by its hydrolytic action on urea and quantification of the ammonium produced with Berthelot reaction. Twenty different samples of soy bean flour with and without thermal inactivation treatments were assessed with the two methods. The new method has a good correlation with that of the AACC--r = 0.9416 (p < 0.0001). It also presents a better specificity because it measures the concentration of the reaction product and shows a more amplified answer than the increase of pH.