Differences in the extent of breakdown of phytate in wholemeal and white flours prepared from three wheats when the flours were made into bread using the three main UK commercial breadmaking processes were investigated. 2. The extent of breakdown (31-46% for wholemeal breads, 88-99% for white breads) was not proportional to the relative processing times involved (1-4 h). The importance of destruction of phytate in the oven is stressed. 3. The phytase (myo-inositol hexaphosphate phosphohydrolase, EC 3. 1. 3.8) activities of the wholemeal flours and the yeast were determined. Re-examination of some information in the literature enabled the relative importance of these activities, and of the various stages of breadmaking, in determining the extent of hydrolysis of phytate to be assessed. 4. Average values for the molar ratio, phytate: zinc, of 22:1 and 0.8:1 were calculated for wholemeal and white breads respectively. The nutritional significance of these results is discussed.
