What is an emulsion?
Emulsions are mixtures of polar and non-polar liquids, and cosmetics are full of formulations combining an aqueous phase with oily ingredients.
What is an emulsifier for?
In order for these mixtures to remain stable, emulsifiers must be incorporated. Thanks to emulsifiers, aqueous and oily phases, which are immiscible, can be mixed.
Emulsifiers are compounds capable of mixing seemingly immiscible liquid ingredients together. When formulating creams, hair products and make-up, we are faced with systems containing substances that would not mix, and to achieve this, emulsifiers are essential ingredients.
Emulsifiers are essential ingredients in the formulation of cosmetic products that combine aqueous and oily phases to form stable emulsions with multiple applications in skin and hair care.
Emulsifiers can be oil-in-water (O/W) or water-in-oil (W/O), and can be hot or cold processed.
An oil-in-water (O/W) emulsifier disperses fine oil droplets through an aqueous base. These O/W emulsions tend to be lighter to the touch. In contrast, a water-in-oil (W/O) emulsion disperses fine water droplets between the oily base ingredients. These emulsions are usually perceived as being greasier to the touch.
The most commonly used emulsifiers contain ingredients of petrochemical origin. However, the cosmetic industry is tending to replace these products with alternatives of natural origin, both in terms of functional ingredients and cosmetic active ingredients, besides there is an increasing interest in natural emulsifiers.
Natural emulsifiers are obtained from oils and fats, or also from sugars and starches of vegetable origin. Ingredients containing ethoxylated substances or ethylene oxide derivatives are excluded from the group of natural emulsifiers.
ISO 16128 standard on natural cosmetics
One criterion for differentiating synthetic emulsifiers from emulsifiers of natural origin is based on ISO 16128, which sets out the definitions of natural ingredients and ingredients of natural origin, as well as their indexes of naturalness. Other similar criteria such as Cosmos certifications also allow to identify the naturalness of natural emulsifiers.
Natural emulsifiers are obtained from renewable sources. This fits with the current consumer concern for products from sustainable sources and with a low impact on the environment.
These ingredients enable the formulation of high-performance cosmetics, with textures that meet the needs of each product, while reducing the carbon footprint and increasing the naturalness of the finished product.
Natural emulsifiers, co-emulsifiers and self-emulsifying bases
For emulsions to be stable they often need to be combined with other ingredients, called coemulsifieres.
Self-emulsifying bases do not require co-emulsifiers, but are considered complete emulsifiers, i.e., a single raw material (consisting of several ingredients) can form stable emulsions.
How to choose an emulsifier?
In the development of a cosmetic emulsion, the selection of the emulsifier is a key factor. The variety of natural emulsifiers available today makes it possible to find a suitable solution for every need.
When selecting an emulsifier, there are crucial factors to be taken into account such as:
- Emulsion type: whether the final product should be a water-in-oil or oil-in-water emulsion.
- Processing: whether the emulsion is to be manufactured at room temperature or whether hot processes are allowed.
- Rheology and texture: the selection of the emulsifier will take into account the desired final viscosity, the type of product flow or texture.
- Compatibility with other ingredients: some components may provide conditions that limit the use of some emulsifiers, such as ionic strength, pH or redox potential.
An emulsion is an unstable system and tends to separate into phases. It is therefore necessary to incorporate stabilising ingredients. To prevent phase separation of an emulsion, synthetic polymers and natural stabilisers can be used, which act as rheology modifiers, blocking the movement of the droplets formed in the emulsion.
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