Study of Highly Concentrated Olive Oil-in-Water Emulsions Stabilized by Palm-Based Nonionic Surfactant

Rheological properties of highly concentrated oil-in-water (O/W) emulsions (HCEs), formed by mixing palm-based nonionic surfactant, C12E6 (HLB = 11.7, CMC = 25 mu M), water and olive oil volume fraction >= 78vol% were investigated. Samples with lower oil volume fraction (< 85%) and surfactant concentration (< 8%) exhibited polydispersity of broader droplet size distribution (DSD). In contrast, samples with higher oil volume fraction (> 85%) and surfactant concentration (> 8%) displayed monodispersity of narrower DSD. The average droplet size decreased with increasing oil volume fraction and surfactant concentration. All frequency sweep experiments exhibited higher G' than G '', representing the predominantly elastic nature of HCEs. The crossover of the ascendant and descendant flow curves of HCEs with higher oil volume fraction (> 85%) and surfactant concentration (> 8%) implied a structural build-up that could give rise to very high stability. The high stability was confirmed through accelerated stability test at 40 degrees C for three months.