Anais do Simpósio Latino Americano de Ciências de Alimentos
Anais do 14 SLACA - Simpósio Latino Americano de Ciência de Alimentos

The objective of this study was to evaluate the effect of cellulose nanofiber (CNF) concentration on the mechanical properties of hydrogels (HG) based on gelatin in its wet and dry state. Soybean straw was chemically treated with a 17.5% NaOH solution (w/v)/15h and bleached using a 4% solution H2O2, 0.3% MgSO4.7H2O and 2% NaOH (w/v) at 90°C/3h. CNF extraction was performed by enzymatic hydrolysis of 3 g soybean straw/150 mL of sodium acetate buffer with 280 µL of an enzyme cocktail Optimash™ VR (DuPont Inc, USA) at pH 4.0 and 50°C/42h, followed by mechanical treatment (15000 rpm/5min) and sonication (70% amplitude/3 min). Hydrogels were prepared with 10 g of gelatin/100 g of solution and 0, 1, 3, 5 of CNF/100 g of gelatin. Wet HGs (diameter=20 mm, height=20 mm) were prepared at 4 °C/24h, and dried HGs were prepared by casting, using 30 g glycerol/100 g gelatin, and their mechanical properties were determined by uniaxial compression and tensile tests (ASTM method D882-10), respectively, using a texturometer (TAXT2, TA Instruments, USA). The fracture stress (FS) or tensile strength (TS), fracture strain (F) or elongation at break (E), and elastic modulus (M), were determined. The mechanical properties of wet HGs loaded with CNF (0-5%) varied between 315.6±12.4 and 116.9±9.9 MPa (FS); 79.2±0.1 and 64.8±0.3% (F) and 4.0±0.2 and 1.8±0.1 MPa (M). Dried HGs presented thickness around 0.291±0.010 mm, and were TS varying from 21.3±1.9 to 17.9±0.4 MPa, but with E and M staying at 47.6±2.4-47.6±1.1% and 3.6±0.4-3.2±0.1 MPa, respectively. The increase of CNF concentration decreased the mechanical properties of the wet HGs, but did not influence these properties in dry HGs. This behavior could be attributed to large aggregates formed by CNF-gelatin complex coacervates at preparing conditions (pH<pI). The mechanical properties of hydrogel in both states are regulated by electrostatic interactions CNF/gelatin.