Potential of defatted marama flour-cassava starch composites to produce functional gluten-free bread-type dough

Abstract

Marama bean is a drought-tolerant oilseed legume. Isolated marama bean protein has high foaming capacity, strong dough extensibility and good elasticity characteristics. The dough properties of composites of defatted marama flour (DMF) and cassava starch (CS) were compared with wheat flour dough with the aim of determining the potential of DMF as a functional nutritious gluten-free ingredient in bread. DMF-CS doughs with similar strength to wheat flour dough could be produced. However, they had much shorter Mixolab development time and stability. Alveography revealed that the DMF-CS doughs could inflate into a bubble, with the 33:67 DMF-CS ratio having the most similar bubble size, extensibility and deformation energy to wheat flour dough; with a higher proportion of DMF (57:43) these parameters were lower. Rheofermentometry showed that the DMF-CS composites could also hold gas produced by yeast fermentation. Confocal laser scanning microscopy revealed that as the proportion of DMF to CS was increased, the DMF protein tended to aggregate rather distribute throughout the dough, probably because the highly hydrophilic marama protein and pectin had great affinity for each other. Nevertheless, defatted marama flour appears to have considerable potential as a functional gluten replacement for making protein- and fibre-rich gluten-free bread.