The effect of protein disulphide isomerase on dough rheology assessed by fundamental and empirical testing

Fundamental rheological tests were carried out on wheat flour dough containing protein disulphide isomerase (PDI, E.C. 5.4.3.1.) and compared with their respective controls. The Controlled Stress Rheometer (CSR) and the Dynamic Mechanical Thermal Analyzer (DMTA) were used. Results from these instrumental tests which are essentially non-destructive were compared with results obtained when using a traditional Extensometer. The possibility of PDI duplicating the effect of potassium bromate was evaluated. Fundamental testing provided more information about the structure of the dough when used under a wide range of different testing conditions. The Extensometer, under the conditions used in this work, was better than the CSR and the DMTA for showing the effect of PDI (50 ppm, flour basis), which seemed to make the dough more elastic the longer the resting time. Although the effect was basically the same as that produced by potassium bromate, it was not of the same magnitude.