Effect of bambara groundnut and sunflower oil contents on the droplet distribution and rheology of a model food emulsion

Abstract

The unending demand for natural food product by consumers has increased research in food emulsion technology towards finding natural emulsifiers and stabilizers to improve the properties of oil-in-water food emulsions. Bambara groundnut although abundant in Africa has been grossly underutilized despite its admiring physicochemical properties. This work therefore explored the use of bambara groundnut flour (BGNF) as the sole natural stabilizer in food emulsion system. The contribution of the main emulsion components viz BGNF and sunflower oil (SFO) on the emulsion stability parameter (droplet size (d_3,2 and d_4,3)) and time-dependent rheological properties of oilin- water emulsions for formulation purposes was investigated. Response surface methodology was used for the experimental design. Droplet size and rheological characterizations were carried out using image analysis and a shear rate controlled rheometer respectively. Both BGNF and SFO had significant influence on the droplet size and time dependent behaviour of the emulsion. Quadratic polynomial relationships were found between the emulsion main components (BGNF and SFO), droplet sizes (d_3,2 and d_4,3) and time dependent properties. The interaction effect of BGNF and SFO was positive while the linear effect was negative on the time-dependent properties of the emulsions. Emulsion formulated with 7% (w/w) BGNF and 40% (w/w) SFO possessed highest structural interaction, stability and manifested as high viscosity. The relationships existing between the quality parameters of red pepper and airdrying temperature were established.

Keywords: Bambara, emulsion, groundnut, rheology, stability