Please activate JavaScript!
Please install Adobe Flash Player, click here for download
ePaper created 2015-04-29, 11:32:09 | version 1.38.0
O ne reason why the product does not perform the way it is expect- ed to can be formulation incom- patibilities. There are some materials which can’t be used in the presence of other materials if you want to get good re- sults. There are even more materials which are active over only a very specif- ic (and sometimes narrow) pH range. When materials are in an incompatible environment, they will degrade and/or lose their bioavailability. Bioavailabili- ty is a measure of how much of the sub- stance present is available for poten- tial uptake or absorption. For example, 100% bioavailable means all that is present is available for uptake or ab- sorption, while a measure of 50% bioavailability means that only half of the substance present in the product is available for uptake or absorption. Where there is only 50% bioavailability, a substance just wouldn’t work to its full potential. Here are a couple of ex- amples that show this phenomenon in commercially available products: • Vitamin C is undoubtedly one of the most difficult substances to formulate with a view to achieving good long term stability. This is especially true when it comes in the form of ascorbic acid, as this is the least stable form of vitamin C. Ascorbic acid needs a rela- tively acidic environment to be stable (pH of 3.5–4.0) and deteriorates quick- ly in the presence of water and/or light. Other forms, for example magnesium (or sodium) ascorbyl phosphate re- quire a pH of 6.0–7.0 to give the best bio-activity and shelf life. There are an increasingly growing number of vitamin C forms and deriva- tives becoming available, all with dif- ferent formulating and stability needs. If, however, a product looks something like beige to brown, then the vitamin C has deteriorated and won’t provide the benefits that could normally be expected. 18 COSSMA 5I2015 FOCUS: ACTIVE INGREDIENTS PRODUCT DEVELOPMENT • Vitamin A requires a pH of 6.0–7.0 to be stable and bioavailable – at more acidic pH levels or in its derivative form (retinyl palmitate), the anticipated re- sults cannot be obtained. In addition, some regulations (e.g. in Australia) limit retinol in cosmetic products* to a maximum of 1%. • Dihydroxyacetone (DHA) reacts with amines, peptides and amino acids of the stratum corneum to produce brown polymers called melanoidins. It will also react with any compounds containing collagen, proteins or nitro- gen that are present in a finished prod- uct formulation. Its efficacy is also af- fected in the presence of anionic sur- factants. Yet in many formulas it is combined with the wrong surfactants or emulsifiers and with collagen or proteins present. So for a convincing tanning product these ingredients have to be avoided. • Alpha hydroxy acids** (AHAs) such as glycolic acid and lactic acid require a pH below 3.85 to be 50% bioavail- able. Finished products containing these ingredients with a pH of 3.0–3.5 will tend to work the best; while those with a pH > 4.0 will have lost most of their bioavailability and efficacy. When a product doesn’t work the way it is expected to, there are 3 main reasons why. Belinda Pilmore from the Institute of Personal Care Science, Australia, takes a look at some fundamental elements to improve the performance of personal care products. If a product con- taining vitamin C has a beige to brown appearance, it won’t provide the expected benefits photo:MikhailRulkov,Shutterstock.com Optimising formulations How to obtain high performance For a convincing tanning product DHA should not be combined with anionic surfactants photo:Photopixel,Shutterstock.com COS1505_18_Pilmore_COS1409_10_Van_Hoeven_GB 27.04.15 07:07 Seite 18 COS1505_18_Pilmore_COS1409_10_Van_Hoeven_GB 27.04.1507:07 Seite 18