Editor’s note: Emulsion science is widespread throughout the personal care industry, providing the means to formulate creams or lotions that contain both oil-miscible and water-soluble components. However, conventional methods for processing such emulsions require significant quantities of energy and time; it has been estimated that heating and cooling alone accounts for over 90% of the total energy cost for the production of an emulsion.1 With the current market focus on eco-friendly materials and processes, cold process emulsion technologies have gained popularity, reducing both the energy demand and manufacturing time required. In this article, traditional emulsions and emulsion processing are reviewed and compared with cold-processed emulsions.
What is an emulsion? As most readers know, an emulsion can be considered a dispersion of one material inside of another, non-miscible phase. Generally, in cosmetics and personal care, the two phases in an emulsion are oil and water/aqueous phases. Emulsion science provides the personal care industry with the means to formulate a cream or lotion that contains both oil-miscible and water-soluble components. For example, emollient components tend to be lipophilic in nature, whereas moisturizers demonstrate mostly hydrophilic characteristics. Other components such as natural extracts, active ingredients, essential oils, fragrances, preservatives, colors and tints all exhibit a preference to either the oil or water phase. Theoretically, oil and water phases are completely immiscible, but there is always a statistical possibility that some oil may dissolve in the water phase and vice versa. The same probability can be applied to other ingredients, so there may be some dissolution, to a minor extent, into the less-favored phase.