Highly viscous dough-forming properties of marama protein

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.

Influence of extraction pH on the foaming, emulsification, oil‐binding and visco‐elastic properties of marama protein

“…The doughs of this moisture content were easy to handle but above this moisture content a batter rather than a dough was formed. The 30% dough moisture content is somewhat lower than used in our previous investigation (38% and 45%) . The linear visco‐elastic range of marama protein preparation doughs was within 5% strain as analysed by dynamic small oscillatory analysis, in agreement with previous findings .…”

“…The 30% dough moisture content is somewhat lower than used in our previous investigation (38% and 45%) . The linear visco‐elastic range of marama protein preparation doughs was within 5% strain as analysed by dynamic small oscillatory analysis, in agreement with previous findings . The storage modulus ( G ′) of the pH 6 extracted protein preparation dough was considerably higher than the pH 8 extracted protein preparation dough, indicating that the dough matrix of the former was much stronger.…”

“…Comparatively lower Tan δ values (0.78–1.27) of pH 6 extracted protein preparation dough shows that the dough matrix was also more elastic compared to pH 8 extracted protein preparation dough (Tan δ 0.99–2.56). In fact, the pH 6 extracted protein preparation dough has a good visco‐elastic balance (Tan δ 0.78 at 100 ω), which approaches that of vital wheat gluten dough (Tan δ 0.55 at 100 ω with a dough moisture content of 45% (dry basis)) . Higher G ′ values and lower Tan δ values are related to a high degree of crosslinking of protein molecules, leading to a strong protein network and providing structural stability to a dough, as is the case in wheat glutenin, where the high molecular weight glutenin subunits are linked together into polymers by disulfide bonds .…”

“…Marama protein, when extracted under slightly alkaline conditions (pH 8), has potentially useful functional properties as it forms highly viscous, adhesive and extensible doughs . The functional properties (biological or techno‐functional) of proteins are directly related to their three‐dimensional structure .…”

“…5 Marama protein, when extracted under slightly alkaline conditions (pH 8), has potentially useful functional properties as it forms highly viscous, adhesive and extensible doughs. 6,7 The functional properties (biological or techno-functional) of proteins are directly related to their three-dimensional structure. 8 In addition, the functional properties of food proteins are further defined by the specific set (combination) of proteins present therein, 9,10 due to their synergistic or antagonistic impact on final functionality.…”