Influence of gliadins on rheology of methylcellulose in 70% (v/v) aqueous ethanol

Rheological properties of methylcellulose in 70% (v/v) aqueous ethanol with and without 100 g L−1 gliadins were studied as a function of methylcellulose concentration C from 0 g L−1 to 20 g L−1. The overlapping concentration of methylcellulose is 7.5 g L−1 in the absence of gliadins while methylcellulose is in the semidilute region at C ≤ 20 g L−1 in the presence of gliadins. The presence of gliadins weakens the shear thinning under strain rate sweep. However, dynamic stress sweep reveals that gliadins may enhance the stress thinning and the solutions at C > 7.5 g L−1 exhibit two Newtonian plateaus which are not observed in the absence of gliadins. The results suggest that the mutual interaction between methylcellulose and gliadin leads to the appearance of two Newtonian plateaus. The methylcellulose solutions in the absence of gliadins do not gel upon heating. On the other hand, gliadins in the solution facilitate the hydrophobic association of methylcellulose molecules upon heating, which leads to the thermal gelation of the solution at C = 20 g L−1.