The emulsifier is neutralized during the emulsification process. Thus in the initial stages, the hydrophobic acid form determines interfacial properties. The stability of the final emulsion is determined by the neutralized form. According to Bancroft's rule this should be predominantly water-soluble in order to stabilize an O/W emulsion.
During emulsification, the thickener is also neutralized and dissolves in the aqueous phase increasing the viscosity. By initially dispersing the thickener in the oil phase, viscosity is kept low at the start of the process. In emulsion manufacturing this is desirable in order to save energy.
Fig. 2 shows a flow curve for an emulsion prepared according to the standard recipe. The curve shows a yield stress at ca 15 Pa.