Rheological characterization of solutions of gelatin with bentonite and tannic acid

This work aimed to study the effect of bentonite particle size, on the rheological properties of gelatin solutions with glycerol, bentonite, and tannic acid. To decrease the particle size, a bentonite solution was centrifuged, recovering only the supernatant (treated bentonite), both control and treated bentonite solutions (0.025 g bentonite/g water) were characterized using atomic force and confocal microscopy. Six solutions, named as C (100, 25, 0, 0, 0), TA (100, 25, 8.47, 0, 0), B (100, 25, 0, 16.83, 0), TB (100, 25, 0, 0, 16.83), O (100, 25, 8.47, 16.83, 0) and TO (100, 25, 8.47, 0, 16.83) g/4500 g water, prepared with gelatin, glycerol, tannic acid, control bentonite, and treated bentonite respectively, were subjected to rheological tests (flow curves and viscoelasticity). The treatment of bentonite reduced the particle size about 200 nm. The solutions O and TO showed shear-thinning behavior (n < 1) with higher moduli (G’ and G") values, than C, TA, B and TB at both 10 and 25 °C. The solutions with treated bentonite produced an improved gel structure, showing less temperature dependence.