Product stability testing helps manufacturers understand how cosmetics, personal care products and pharmaceuticals perform over time under defined storage conditions.
It provides information about changes in the formulation and whether further development work may be required. At Delta, stability testing forms part of the wider product development and manufacturing process, helping brands understand how their product performs over time.
What Is Product Stability Testing?
Product stability testing monitors how a product changes over time under defined storage conditions.
Depending on the product, this can include changes in its appearance, texture, formulation or microbiological results.
The goal is to assess whether the product continues to meet the specifications established for it during development.
Stability testing can provide information that supports shelf-life assessment, product specifications, relevant regulatory requirements and ongoing product development decisions.
Having a structured testing protocol provides a consistent way to monitor the product and record changes throughout the study.
Why Is Stability Testing Important?
A product may look and feel as expected when a lab sample is first developed, but the development team also needs to understand how it behaves over time.
Stability testing can help identify changes such as:
- Separation
- Changes in colour
- Changes in texture or viscosity
- Changes that fall outside the product’s defined specifications
The results provide information that can help determine whether the formulation is ready to continue through development or whether further review is required.
What Is Assessed During Stability Testing?
The characteristics assessed during a stability study will depend on the individual product and its requirements.
Physical Stability
Physical stability looks at changes that can be seen or measured in the product over time.
This may include changes in colour, texture or viscosity, as well as separation, sedimentation or crystallisation.
These observations help the development team understand whether the product is maintaining its intended physical characteristics throughout the study.
Chemical Stability
Where relevant, stability testing may include analytical testing to monitor specified active ingredients over time.
The testing required will depend on the product type, formulation and applicable requirements.
Microbiological Testing
Microbiological testing may also be included as part of the testing program where relevant to the product.
For some products, particularly water-based formulations, this may include:
- Microbial testing
- Preservative efficacy testing
The appropriate microbiological testing will depend on the formulation and product requirements.
How Stability Testing Works at Delta
At Delta, stability testing is planned around the individual product and its requirements.
Before testing begins, a stability protocol is prepared for the product. This sets out how long the study will run, the storage conditions being used, when samples will be assessed and what will be reviewed.
Having the protocol in place provides a consistent way to monitor the product throughout the testing period.
Temperature and Humidity Conditions
Products are stored under defined conditions during a stability study so changes can be monitored over time.
At Delta, a typical long-term stability condition is 30°C and 65% relative humidity (RH).
Other conditions may be used depending on the product and its requirements.
Samples are assessed at scheduled intervals throughout the study rather than being reviewed only at the beginning and end.
Stability Requirements Can Vary
There is no single stability testing program that applies to every product.
The requirements depend on the type of product, its formulation and the regulatory pathway that applies to it.
For pharmaceutical or therapeutic products, stability data may be required to support areas such as expiry dating, storage conditions and product registration.
Cosmetic and personal care products will have different considerations depending on the individual formulation and product requirements.
The stability program should therefore be developed around the product rather than applying the same testing approach to every formulation.
Reviewing Stability Results
Samples are assessed at scheduled points throughout the stability study and the results are recorded.
Depending on the product, this may include changes in relevant product specifications, pH or viscosity measurements, microbiological results and other observations made during the study.
The results are reviewed against the specifications established for the product.
If something falls outside those specifications, further review or development work may be required before the product progresses.
The purpose of this review is to understand how the product is performing over time and identify anything that may need further investigation.
When Does Stability Testing Happen?
Stability testing is considered as part of the wider product development process.
Once a formulation reaches an appropriate stage of development, the relevant stability study can begin.
Because stability studies take place over a defined period, brands should allow for testing within their overall product development timeline.
If results indicate that further formulation work is required, additional development and testing may also need to be considered.
For brands new to manufacturing, this is an important part of understanding the time between approving a lab sample and moving towards commercial production.
Stability Testing at Delta
Delta works with cosmetic, personal care and pharmaceutical products, with stability testing considered as part of the wider development and manufacturing process.
Depending on the product, Delta can support stability protocols developed around the product and its requirements, defined storage conditions, scheduled sample assessment and the recording and reporting of stability results.
This provides brands with information about how their product performs over time and whether anything needs to be reviewed before the next stage of development.
Do Brands Need to Understand the Science Behind Stability Testing?
Not in detail.
Brands do not need to know how to design a stability protocol or interpret every technical measurement before speaking with a manufacturer.
What is useful is understanding that stability testing takes time and provides information about how a product performs after the initial formulation stage.
The formulation, quality and manufacturing teams can then determine what needs to be assessed for the individual product.
For a brand, the important questions are usually much simpler: what testing does my product need, when does it happen and how does it fit into the overall development timeline?
Need Support With Product Stability Testing?
Delta works with cosmetic, personal care and pharmaceutical brands to develop stability testing programs suited to the product and its requirements.
Speak with Delta’s team about stability testing requirements for your product.