I’m inspired to write this article because in my previous article I touched upon the overview of the stability study and now we will go a little deeper in it to understand more importance of stability study and shelf life of the cosmetic formulation.

Why stability study is required

Stability study is required for the assessment of formulation, product container compatibility with the formulation, comparison of lab batch and production batch because of the process, to compare lab batch ingredients and production batch ingredients which were purchased, to compare the lab batch and production batch with the different user equipment, to compare the lab batch which are filled containers with the production batch filled in purchased containers, to compare the old vendor vs alternate vendor for the ingredients.

Test parameters need to be defined specifically in the specification to test the product samples so that the Quality Control team can easily do the testing of the final production samples.

Stability and compatibility of the product

Ideally, we need to check stability in two main distinct components, one is internal chemical and physical stability of the product or ingredients which are added into the formulation and another one is a product and primary packaging interaction stability.

We at Mikasa Cosmetics (Division of Meso Private Limited) are doing product development along with the complete stability study. In my 17 years of carrier, I had seen many issues and adverse effects on products or containers so, for every formulation, product stability and compatibility need to be done compulsorily to ensure the product’s quality as well as product’s shelf life. We have many examples of products that are rejected by consumers due to the lack of stability.

Label from the packaging leach out, microbial contamination in the products, bad smell coming from the products, rancidity smell coming from the products, water separation in the products, color change in the products over a period of time, these all are the example of not doing products stability and many times consumer get the skin problem and file case in court and entrepreneurs have to pay the very high penalty and brand will vanish due to this, so our opinion is that don’t launch any product without complete stability as well as compatibility study.

A stability study is required to propose the shelf-life of the cosmetic product, shelf-life of the cosmetic product means the product is stable and within the set of parameters called specification in the container when it's packed till it is sold. When a product is made, one needs to create a draft specification along with the set parameters, and finalize the specification after completion of stability study, and based on this stability study shelf-life can be determined. Specification of cosmetic products needs to be finalized with the help of the country’s cosmetic standards like the Bureau of Indian standard (BIS) is applicable for India.

In the instability study, we need to evaluate the parameters like change in color, odor, other physical changes like separation, creaming, sedimentation, etc., pH of the product, Viscosity or rheology properties of the formulation, weight changes, microbial result, and many more.

There are many studies available to give more confidence for stable formulation and shelf-life like stress study, UV study, centrifuge study, freeze and thaw study, sunlight study, PET (preservative efficacy test), etc.

Stress study is mainly to check the emulsion stability in a shorter time like in any emulsion-based product it is required to keep at 50 to 55°C for 15 days to 30 days and in this period if the emulsion is not breaking it means that the product emulsion will stay stable for 2 to 3 years at ambient temperature. Another example is that if any products which contain suspended beads or scrubbing particles also need to be checked in the same way. If beads or scrubs are not settling down within this time period, it means that the beads or scrubs will not settle down up to the shelf life. We here at Mikasa Cosmetics (Division of Meso Private Limited) do this kind of study for each and every formulation to get more confident about the newly developed products.

UV study and Sunlight study are mainly to check the color stability, all the developed formulation with the final color needs to keep under UV chamber and sunlight for 1month and we can get the idea about the color stability if color is changed or faded, formulator scientist has to revise the formulation, needs to add color stabilization molecule like UV absorber (benzophenone-3, Ethylhexyl methoxy Cinnamate, Sodium metabisulphite, etc.) each and every molecule have their own positives and negatives so based on the literature and your own experience it needs to be selected for color protection molecule, for example, if sodium metabisulphite used in emulsion-based products, sometime it will reduce the viscosity of products and sometimes it will break the emulsion so it is to be used after doing thorough literature study as well as stress study.

Centrifuge test is mainly to check the emulsion separation as well as any sedimentation in the products, ideally, a sample is to be tested in a centrifuge at 3000rpm and for 1 to 2 hours, further if any emulsion separation, sedimentation is not observed in the product, it means that formulation is ok and if any separation and sedimentation are observed, a scientist has to modify the formulation and again needs to recheck this test.

First, it needs to finalize the formulation and be approved by the marketing team, that needs to prepare a stability batch and needs to finalize the test parameters as per the county standard and needs to conduct the stability test and after 6months of accelerated stability data it needs to fix the finished product specification and that specification needs to be used at the time of production batch, production batch needs to pass the specification after that only production batch is to be transferred for the filling and packing.

A preservative efficacy test is required to check the preservative system is effective or not. If the formulation is not passing the preservative efficacy test, needs to improve the preservative system or needs to change the preservative system and again check the preservative efficacy test (PET) and freeze the preservatives for that formulation.

Some of the things formulation scientist has to keep in mind like parabens preservative efficacy will not work or will work less in presence of polysorbate 20 because it neutralizes the preservative efficacy. We at Mikasa cosmetics (Division of Meso Private limited) keep all the things in mind and design the formulation.

I firmly believe that “there are no shortcuts for success” same rule applies in cosmetics also that there is no shortcut to a stable product/ formulation without the complete stability study.