The decomposition of S35-labeled potassium persulfate by flour doughs
Small, Donald George
In some of the more recent studies on the improver problem, one line of attack has been the determination of the rate of reduction or decomposition of the improvers by flours and doughs. Thus the decomposition of bromate in fermenting and nonfermenting doughs has been followed by Cunningham and Anderson (12) by means of amperometic titration, while Lee, Tkachuk and Finlayson (13) have measured the conversion of bromate to bromide in fermenting and nonfermenting doughs and in baked bread by use of radioactive bromine -82 as tracer. Detailed studies on persulfate, however, are still lacking. A fluorometric method for the determination of persulfate in flour and dough has been reported (14). It was claimed to be sensitive for the quantitative determination of as little as 5 to 10 parts ammonium persulfate per million parts of flour or dough. The method involves the re-oxidation of leuco-fluorescein to fluorescein through the action of persulfate ion. Under controlled conditions, the intensity of the developed fluorescence bears a reproducible relationship to the persulfate content of the sample. Since persulfates are used only in the order of 200 p.p.m., the measurement by ordinary analytical means of such minute amounts of improver in relatively large quantities of flour is, at best, rather difficult. The application of radioactive tracers, with its high sensitivity and the ease of identification of the labeled compounds by the carrier technique, provides an excellent tool for determining the fate of flour improvers in dough systems. Conn and coworkers (15), for example, have used I131-labeled potassium iodate to investigate the decomposition of iodate during the baking of bread, and have shown the major decomposition product to be iodide. In the present work, the degrees of reduction of s35-labeled persulfate to sulfate are determined for water slurries of flour and of gluten, and for nonfermenting doughs prepared from ordinary and defatted flours.