Chemical composition and physical properties of modified dietary fibre sources

The influence of thermal treatments on the chemical composition and the physical properties of yellow pea hulls, apple pomace and depectinised apple pomace were determined. The chemical composition of yellow pea hulls and apple pomace was altered only slightly. With depectinised apple pomace, however, the heat treatments led to a significant loss of the total dietary fibre (TDF) content. Water uptake, water binding capacity, rheological behaviour in the farinograph and oil absorption were determined before and after boiling, autoclaving and extrusion cooking. The physical properties of all samples were considerably affected by the thermal modifications. Whilst in cooked dietary fibre samples the water uptake, the water binding capacity and the oil absorption was always enhanced, the influence of autoclaving and extrusion cooking on the physical properties depended very much on the dietary fibre source. Yellow pea hulls showed unchanged or slightly increased values, while the results for the two apple pomace preparations were lower compared with the untreated samples. The differences in the farinogramsiwere less obvious since the dietary fibre content in the dough mixtures was only in the range of 10–20%.