Abstract:
Marama bean is an indigenous Southern African oilseed legume with an unusual
protein composition. Hence, its rheological properties were studied. Marama protein
formed a highly viscous and extensible dough when compared to soya and gluten.
With a dough of 38% moisture, marama protein extensibility was very high (304%),
twice that of gluten and soya, and this increased considerably (> 3 fold) when the
moisture content was increased to 45%. With added peroxidase, the storage modulus
(G') of marama protein dough increased with time, suggesting the formation of new
and strong protein networks. Dityrosine crosslinks were detected in the doughs.
Marama protein showed a single transition with a denaturation temperature higher
than soya glycinin. Marama protein appeared more hydrophobic and contained more
β-sheet structure than soya. Thus, the highly viscous and extensible rheological
behaviour of marama protein is probably related to its high β-sheet conformation,
hydrophobic interactions and tyrosine crosslinks.
