Effect of p H, emulsifier type and concentration on physical stability of oil-in-water emulsions

To explore the influence of emulsifiers and p H on physical stability of walnut oil- in- water emulsion, the emulsions stabilized by whey protein isolates, sodium dodecyl sulfate ( SDS) , dodecyltrimethylammonium bromide ( DTAB) , and Tween20, respectively, were investigated.And the required minimum concentrations of emulsifiers to form a stable walnut oil- in- water emulsionwerealso determined. Results showed that the influence of p H on the emulsifying effect of cationic surfactant and nonionic surfactant wasremarkable.Under the condition of p H3.0 and7.0, the required minimum concentrations of DTAB were 0.8% and 2.0%, respectively. Meanwhile, the required minimum concentrations of Tween20 were 0.6% and 0.3% at p H3.0 and 7.0, respectively. But forampholytic surfactant WPI and anionic surfactant SDS, the influence of p H ( except for isoelectric point) was non- significant.The above phenomenon indicated that the physical stability of walnut oil- in- water emulsions was greatly influenced by different p H and emulsifiers.