OWemulsies

OWemulsies, or oil-in-water emulsions, are a type of colloidal dispersion in which oil droplets are dispersed in a continuous water phase. They are stabilized by emulsifiers and often by thickeners that modify viscosity. In O/W systems the external phase is water, giving products that feel light and rinse off easily compared with water-in-oil emulsions.

Common emulsifiers for O/W systems include nonionic surfactants such as polysorbates and sorbitan esters, as well as lecithin. Co-emulsifiers and thickening agents (gums, carbomers) improve stability, texture, and water resistance. Droplet sizes are typically submicron to a few microns; smaller droplets can improve clarity and stability but require more energy to create.

Preparation methods include high-shear mixing, rotor-stator homogenization, high-pressure homogenization, and phase-inversion techniques such as phase-inversion temperature or spontaneous emulsification.

Applications span cosmetics (creams, lotions), foods (dressings, mayonnaise), and pharmaceuticals (topical gels and creams). In cosmetics, O/W systems are common for moisturizing products, while in foods they appear in products like dressings and mayonnaise.

Stability considerations include creaming, coalescence, and Ostwald ripening. Stability is influenced by emulsifier type, phase ratio, droplet size, pH, temperature, and electrolytes. Formulators use appropriate hydrophilic-lipophilic balance values and thickening agents to improve shelf life and texture. O/W emulsions can be more susceptible to water loss or microbial growth if not properly preserved.

Compared with water-in-oil emulsions, O/W emulsions generally have a lighter feel and are easier to rinse, but may offer less oil-based protection and water resistance in certain products.