Sourdough fermentation of wheat fractions rich in fibres before their use in processed food

Fibre-rich fractions of wheat are an important source of minerals but also contain considerable amounts of phytic acid, known to impair mineral absorption. This study explores the efficiency of wheat bran sourdough fermentation on phytate hydrolysis and mineral solubility, in comparison with whole-wheat flour. In vitro trials were performed to assess the consequences of the addition of calcium carbonate (CaCO3), an alkalinising salt, on phytic acid breakdown and mineral bioavailability during sourdough fermentation. Sourdough fermentation was found effective for solubilising minerals in whole-wheat flours but was less effective with bran. In addition, sourdough acidity was blunted by the addition of CaCO3, whereas degradation of phytic acid remained effective. Despite extensive breakdown of phytic acid (almost 70%), the addition of calcium exerted a very negative effect on zinc solubility. In conclusion, a pre-fermentation process of whole cereals or bran, in suitable conditions of hydration, allows degradation of the major part of phytic acid and optimal mineral bioavailability. (C) 2007 Society of Chemical Industry.