Baobab polysaccharides as emulsifiers

Abstract

Polysaccharides extracted from fruits and leaves of baobab tree (Adansonia digitata) were assessed for their emulsifying capacity. Emulsions were formed at acidic pH (pH 2.0 and ϕ = 0.1) and were investigated by means of droplet size distribution analysis, ζ-potential measurements, and interfacial composition analysis. Despite the macromolecular differences of baobab polysaccharides all emulsions were formulated at concentrations resulting in comparable zero shear viscosity of the continuous phase allowing structure vs. function relationships to be made. Emulsions made with fruit polysaccharides formed finer droplets and exhibited good long term stability than those formulated with leaf polysaccharides. Stability was achieved by formation of thick interfacial layers, as evidenced by the large polysaccharide interfacial loading (Γpolysaccharide 13.8 or 20.7 mg m−2) that created an effective steric barrier against droplet growth, whereas proteins did not seem to play central role. Fruit polysaccharide emulsification performance at acidic pH was attributed to their compact conformation at the interface that is linked to their structure. Conversely, the presence of rhamnogalacturonan segments in leaf polysaccharides resulted in chain desorption and poor emulsion stability. Overall, it has been shown that baobab fruit polysaccharides could be suitable emulsifiers for a range of technological applications that require low pH stability.