Effect of bacterial nanocellulose addition on the rheological properties of gluten-free muffin batters

Replacing wheat flour in bakery products is a technological challenge as the absence of gluten affects rheological characteristics of uncooked batter which are directly related with final product quality. Bacterial nanocellulose (BNC) is a novel hydrocolloid which could improve batters rheological behavior. Five levels of BNC (0.06, 0.12, 0.18, 0.24, and 0.30 g BNC/100 g) and a control were employed to study its effect on rheological behavior of gluten-free muffin batters. Specific gravity, back extrusion, steady flow viscosity, and rheological assays (temperature, frequency and stress sweeps) were performed. Higher BNC levels increased firmness, viscosity, and consistency indexes. The lowest specific gravity was obtained for 0.12-0.18 g BNC/100 g indicating that more air was trapped. Flow curves were fitted with a modified Cross model; eta(0) and the characteristic relaxation time increased when BNC was added. Batters with BNC showed greater G' and G than control during and after thermal treatment. Curves were modeled showing that molecular mobility decreased with BNC level, related to a more structured matrix. Temperature sweeps showed two transition temperatures. T-1, dependent on BNC level, ranged from 81.0 +/- 0.8 degrees C for 0.06 g BNC/100 g to 64 +/- 2 degrees C for 0.24 g BNC/100 g or more, it might be related with BNC-starch interactions. T-2 was unchanged (86.1 +/- 0.6 degrees C) and consistent with starch pasting temperature. Levels of dry BNC between 0.12 and 0.18 g/100g batter resulted in viscous systems that could entrap more air and may result into higher volume of the baked products.