Observing unwanted changes to a body cream



I have been testing out a new preservative.  It’s based on an organic acid and some polyols. The INCI was not offensive even for the most purest of natural formulators or customers so I thought it would be a nice idea to try it. Also, it looked to be easy to use as compared to others on the market.  It has also been used by some pretty big brands as the only preservative so I know it can work.

Process wise, it can go in the heated water phase up to 90 c so if you have problems controlling your temperature it won't make much of a difference.  It can also go in the cool down phase as well and is recommended for use in just about any formulation type you can think of - anhydrous ones like cleansing balms, emulsions like creams and lotions, solutions like toners and detergent surfactants like shower gels and facial cleansers. All in all I have been pretty excited about using it. The manufacturers only advice was that care should be taken when using with clay's as the metal ions  can interfere with the formula and change its colour to 'faintly mild orange' which, they say, is barely detectable.   So, I thought bearing all this in mind, it would be perfect to use in an emulsion.

I made a body cream in the normal way, including the preservative as directed by the manufacturer.  I decided to put it in after the emulsion was formed (at around 60c)  and it initially thinned the emulsion which was a worry, however it did thicken nicely after 24 hours. I did a quick and dirty 48 hour stability test at an unusually high temperature and it was stable - it did not separate, there were no changes in colour or scent.  All in all it looked promising. However, after just over two months at room temperature, as you can see from the picture, the colour changed from a nice creamy colour (left) to the salmon pink/orange colour on the right .

My thoughts are that although there is no clay in the formula, there is enough metal ions floating around to cause this colour change.  So what would be the plan? First off,  I am going to use a chelating agent like Sodium Phytate/ Phytic Acid which will help bind the metals and hopefully stop it from discolouring the product.  

I might also see if it is light that causes the problem by keeping a batch in a cupboard or a in a dark glass jar.

So there you go! Although this preservative looked promising it has had some problems which could only be identified by experimenting with the product. This is also a reason why performing stability tests is so important - without waiting and observing we do not know how our products will change over time.