Factors affecting sorghum protein digestibility

In the semi-arid tropics worldwide, sorghum (Sorghum bicolor (L.) Moench) is cultivated by farmers on a subsistence level and consumed as food by humans. A nutritional limitation to its use is the poor digestibility of sorghum protein when wet cooked. The factors affecting wet cooked sorghum protein digestibility may be categorised into two main groups: exogenous factors (grain organisational structure, polyphenols, phytic acid, starch and non-starch polysaccharides) and endogenous factors (disulphide and non-disulphide crosslinking, kafirin hydrophobicity and changes in protein secondary structure). All these factors have been shown to influence sorghum protein digestibility. More than one factor may be at play at any time depending on the nature or the state in which the sorghum grain is; that is whether whole grain, endosperm, protein body preparation, high-tannin or condensed-tannin-free. It is proposed that protein crosslinking may be the greatest factor that influences sorghum protein digestibility. This may be between ?- and ß-kafirin proteins at the protein body periphery, which may impede digestion of the centrally located major storage protein, a-kafirin, or between ?- or ß-kafirin and a-kafiri

Insights into SusCD-mediated glycan import by a prominent gut symbiont

In Bacteroidetes, one of the dominant phyla of the mammalian gut, active uptake of large nutrients across the outer membrane is mediated by SusCD protein complexes via a “pedal bin” transport mechanism. However, many features of SusCD function in glycan uptake remain unclear, including ligand binding, the role of the SusD lid and the size limit for substrate transport. Here we characterise the β2,6 fructo-oligosaccharide (FOS) importing SusCD from Bacteroides thetaiotaomicron (Bt1762-Bt1763) to shed light on SusCD function. Co-crystal structures reveal residues involved in glycan recognition and suggest that the large binding cavity can accommodate several substrate molecules, each up to ~2.5 kDa in size, a finding supported by native mass spectrometry and isothermal titration calorimetry. Mutational studies in vivo provide functional insights into the key structural features of the SusCD apparatus and cryo-EM of the intact dimeric SusCD complex reveals several distinct states of the transporter, directly visualising the dynamics of the pedal bin transport mechanism

Rheological properties of Danwake flour blends from sorghum, wheat and cassava bases

The rheological properties of seven danwake flour blend formulations from sorghum, wheat and cassava bases were investigated. The different ingredients in the danwake were sorghum flour, cowpea flour, wheat flour, cassava flour, baobab leaf powder, and trona (sodium sesquicarbonate) (kanwa). The viscosity of the flour blends were determined using standard methods. The viscosity of the danwake flour blends decreased with the increase in shear rate, a case of pseudoplasticity. The viscosity also decreased with the increase in temperature for all of flour blends but increased with the increase in cowpea flour content in sorghum based danwake flour blends. The Power law indices obtained which were less than 1.00 (n < 1.00) confirmed the non- Newtonian and possibly pseudoplastic behavior of the pastes (r = 0.89 – 0.99). The Power law indices were significantly (p < 0.05) affected by the flour blend formulations and by temperature. The activation energies showed that pastes from sorghum based danwake with 7% cowpea and 30% cowpea gave the highest (32.27 MJ/mol) and the least (16.30 MJ/mol) sensitivity to temperature changes, respectively.Key words: rheological, properties, danwake, sorghum and wheat