Wheat proteins can be balanced with supplementation of dried yeast; however the dramatic increase in protein biological value was accompanied by the impairment of dough or pasta quality. These negative findings might be the result of high proteolytic enzyme activity of yeast. To confirm this hypothesis we investigated the effect of baker's yeast proteinases on gluten at two incubation temperatures, 30 degrees C and 50 degrees C resp. after 10, 30 and 60 min incubation time. Reaction was followed up by determination of protein solubility. Results showed a significant increase in protein solubility at both temperatures. The effect of yeast on S-S bond content was determined from dough samples after 30, 60 and 90 min incubation. After 60 min significant increase of S-S bonds occurred, this drastically decreased after extension of leavening time. As the main proteinase activities of baker's yeast are influenced by propagation parameters (glucose content and aeration intensity) while high proteolytic level causes gluten degradation, this should be taken into consideration in the yeast production.
