Formulation and characterisation of wheat bran oil-in-water nanoemulsions

Wheat bran oil (WBO) has been reported to have an important content of bioactive compounds, such as tocopherols, alkylresorcinols, steryl ferulates and other phenolic compounds; however, its poor solubility in water systems restricts its applications in the food industry. This study is focussed on the formulation of oil-in-water (O/W) nanoemulsions of WBO in order to improve the bioaccessibility of its active compounds. The influences of oil concentration, surfactant type and concentration, and emulsification method, on the droplet size and stability of the nanoemulsions were investigated. Response surface methodology was used to optimise the conditions for preparing stable nanoemulsions with the minimum droplet size. The optimal nanoemulsion was obtained when 1% of WBO and 7.3% of a surfactant mixture of Span 80 (37.4%) and Tween 80 (62.6%) were emulsified in water by high intensity ultrasonication for 50 s after pre-emulsification with a high speed blender during 5 min. The optimal nanoemulsion showed good stability over time and antioxidant and tyrosinase inhibitory activities, which make it suitable for use in food applications.