Thermal Gelation of Proteins from Cajanus cajan Influenced by pH and Ionic Strength

Cajanus cajan [pigeon pea (PP)] is an important legume crop for subsistence agriculture and its seeds are an alternative plant-based protein source. PP protein isolates (PPI) are able to form heat-induced gels that could be used for food applications. The aim of this work was to study the influence of pH (2.1, 3.9, 6.3, and 8.3) and ionic strength (& mu;) (0.10 and 0.54) on thermal stability and thermal gelation of PPI obtained by alkaline extraction (pH 8.0) and isoelectric precipitation. Thermal stability of PPI changed with pH variation at low ionic strength (& mu; = 0.10), decreasing this dependence with the increase of ionic strength (& mu; = 0.54). At & mu; = 0.10, gelation capacity of PPI was lower at pH 2.1 and pH 3.9. These gels presented a coarse network, which entails low WHC. At pH 6.3 and pH 8.3, gels showed a solid-like character with a compact and homogeneous matrix, with better WHC. At & mu; = 0.54, gel formation was favoured at pH 2.1 and pH 3.9. G & PRIME;(20)/G & PRIME;(95) ratio values and differential solubility results suggest that hydrogen bonds and electrostatic interactions could play an important role in gel formation at pH 6.3 and pH 8.3.

Automated summary

The aim of this study was to investigate the effect of pH and ionic strength on the thermal stability and thermal gelation of PP protein isolates (PPI) obtained by alkaline extraction and isoelectric precipitation. The results showed that the thermal stability of PPI changed with pH variation at low ionic strength, while this dependence decreased with the increase of ionic strength. At low ionic strength, gelation capacity of PPI was lower at pH 2.1 and pH 3.9, while at pH 6.3 and pH 8.3, gels showed better water holding capacity.