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Summary Three manufacturing procedures using a slow propeller mixer, a labyrinth and a valve homogenizer were used for the preparation of emulsions. Three oil phases and fifteen pairs of emulsifiers were used giving a range of HLB values. These homogenizers gave more stable emulsions than the propeller mixer in the majority of cases although several times the reverse was the case. To interpret these reversals several mechanisms are suggested: the mechanical engergy applied to the system modifies the equilibrium of the interaction oil/emulsifier; homogenization gives a considerable increase in the contact to the point where the interfacial film is deficient in surface agents and is unable to stablilise completely the system or the emulsifier is no longer in sufficient concentration in the aqueous phase to play its role in viscosity modification which appears to be the case in non homogenized emulsions.

Synopsis The influence of the following hydrophilic polymers on the stability of emulsions has been studied: sodium carboxymethyl cellulose, hydroxyethyl cellulose, agar-agar, water dispersible clay, and a neutralized polyethylene acid. The oil phases used were paraffin oil, olive oil and a synthetic C(8)-C(12) triglyceride. The other emulsifiers were non ionic-types. After 12 months storage at room temperature, olive oil proved to be the most difficult material to emulsify. The hydrocolloids did not give uniformly better stability to the emulsions and the polyacrylic acid gave the best stability of the colloids tested.