Bacterial cellulose as stabilizer of o/w emulsions

O/w emulsions (10% wt olive oil) were prepared at pH 3.8 stabilized by different types of cellulose (HPMC, CMC, bacterial cellulose - BC) at total concentrations varying from 0.1 to 1% wt. Two emulsification methods were used: high shear mixer and ultrasound. The latter was found to improve all emulsions stability as it decreased their serum index (SI) from 46 to 3 %. BC emulsions exhibited the largest droplet size (d(3,2) = 26 mm) and the highest stability (SI = 3%), which is typical for particle-stabilized emulsions. This is due to the flocs of BC fibrils adsorbed to the surface of the oil droplet and formed a strong network which prevents droplets' coalescence. The HPMC emulsion exhibited Newtonian-like behavior, however the emulsions prepared with all the other types of cellulose exhibited shear-thinning with yield stress behavior. In BC emulsions, storage modulus (G') values were higher than loss modulus (G'') values, typical for weak gel-like behavior, while in HPMC and CMC emulsions loss modulus exceeded the storage, indicating a fluid-like behavior. BC emulsions were not affected by changes in pH, temperature or ionic strength, as their SI remained the same, unlike the emulsions prepared with CMC or HPMC, which were depended for the environmental stresses. All in all, the use of BC as a stabilizer showed to increase emulsions stability compared to other commercial celluloses. (C) 2014 Elsevier Ltd. All rights reserved.