Fragrance stability: common problems avoided

The most common problems with perfumes relate to colour as perfumes can cause immediate colouration or cause colour changes over time. Perfumes can be involved in other appearance changes, for example; changes in viscosity of emulsion systems and the cause of sediment appearing in alcoholic fragrances. Additionally, compatibility and age related odour changes can occur. Customers are usually more confident in the ability of their eyes than their noses to judge if a product is acceptable and an appearance change can act as a flag to perceived or actual issues with their favoured cosmetic product. Understanding and minimising potential adverse effects from fragrances is just one of the useful tools in the toolbox of product formulators and designers. Stable products are a legal requirement under the Cosmetic Directive. The Cosmetic Product Safety Report must include information about stabililty of the product under reasonably foreseeable storage conditions. This also relates to durability – or shelf life months after opening. A perfume in concentrated oil form, if stored well, is usually stable for years. Once a fragrance is introduced into a cosmetic application things can be trickier. It makes commercial sense to provide stable products for many reasons including avoiding customer dissatisfaction and preventing different batches of the same product looking different on a sales shelf. So, perhaps it may seem simpler to use fragrances which are colour neutral and avoid any ingredients with potential for change? Is this even possible or desirable? What is a stable perfume? For the purposes of this discussion I mean a perfume which is stable in the cosmetic product base and packaging at the percentage used in the conditions of expected use. It does not mean no change or colour allowed. Often there are competing requirements between product attributes and some compromise is required.

Discolouration

Some fragrances require discolouring ingredients to smell authentic. A good example is vanilla which naturally contains vanillin, responsible for providing the distinctive odour. Vanillin, along with ethyl vanillin and several other commonly used fragrance materials can contribute to the discolouration of cosmetic products. It depends on the level used in the fragrance and the type of cosmetic product also. What are the possibilities to reduce discolouration problems? Is it desirable to avoid discolouring ingredients altogether? For certain products this would be the right thing, to confine the fragrance choices and sacrifice some odour character in pursuit of a stable white product. Other approaches can be to add UV absorbers to slow down the changes; reduce percentage of discolouring materials or perfume to cause fewer issues; or where possible to alter the pH of the product to slightly acidic to inhibit discolouration – this can be really effective. If the desired fragrance means colouration or discolouration is a reality, then careful choice of packaging can either limit visibility of any issues or incorporate the effect into the design.