Effect of Persian gum concentration, oil content, whey protein concentrate, and pH on the stability of emulsions prepared by ultrasonic homogenizer

Abstract

In this study, the effect of Persian gum (PG) concentration (0.25-1%), oil-phase volume (5-15%), the presence of whey protein concentrate (WPC) 1%, pH (3.5–8), and storage time (up to 20 days) on the stability, rheological properties, particle size distribution, as well as microstructure of emulsions prepared by ultrasound homogenizer was investigated. According to findings, PG was able to stabilize the emulsions particularly at higher concentrations likely via viscosity increasing but not due to its effect on lowering the interfacial tension. In addition, at higher pH (8) values, the stability of emulsions increased, whereas at pH 3.5, the rate of phase separation increased. Moreover, at pH 7 the stability of emulsions containing WPC was significant, while the phase separation observed at the presence of Persian gum (0.5­–1%), probably due to depletion flocculation and thermodynamic incompatibility. Moreover, at pH 3.5 and 5, the creaming occurred with high rate likely because of the bridging occurred between protein coated droplets and gum and protein–gum coated ones. It can be concluded that firstly, the higher levels of gum lowered droplet coalescence and secondly, soluble part of PG as an adsorbing polymer was not able to bind to WPC coated droplets at neutral pH.

Keywords

• depletion flocculation
• emulsion
• persian gum
• thermodynamic incompatibility