Simplify Your Approach to Product Stability Analysis in Powders

Product stability analysis doesn’t need to be complicated. Join Dr. Zachary Cartwright and Mary Galloway to explore the science of powder stability, flow and caking – and a simple method to control them. 

Whether in the food or pharmaceutical industry, managing moisture in powders doesn't have to be complicated. In today's webinar, we're going to show you why. While other methods can be lengthy and complicated, using dynamic dewpoint isotherm (DDI) curves is the simplest, quickest, and most straightforward way to gather valuable data and pinpoint at what point issues such as caking, clumping, and deliquescence will occur in a powder and affect food product stability. 

Let's look at some of the most common problems facing powder products and how a DDI can help predict and improve quality.

Caking and clumping

In both the food and pharmaceutical industries, the vast majority of issues with powder are related to the adsorption of water – when water on the outside can move into the powder and causes it to enter one of the five stages: wet, sticky, agglomerate, compact, or liquefaction. 

To prevent caking and clumping, you first have to predict it by modeling how the powder will react to the three major factors that influence these processes: water activity, time, and temperature. A high-resolution DDI isotherm is generally the only way to determine the critical water activity level when these changes will occur in the powder and affect food product stability. Armed with the knowledge of the sorption properties and critical water activity — plus information about your packaging and storage conditions — you can predict and improve food product stability and shelf life. 

The process of caking and clumping in crystalline powder differs from other powders due to different particle sizes and shapes and its tightly bound structure, making it harder for moisture from the outside to penetrate the surface. As a result, moisture adheres to the surface of crystalline powders until it reaches a critical water activity when the powder immediately goes into the deliquescence stage. This process can also be pinpointed using a DDI. 

Predict & Avoiding

Figure 1. Dynamic dewpoint isotherms allow you to predict when free-flowing powder will enter a caking/clumping zone.

Moisture migration

The ability to predict how adding ingredients to a product will affect food product stability due to changes in water activity or how a final product will react is essential to research and development teams looking to accelerate the formulation process and get their products to the market quickly. The good news is we can gather stability data accurately and rapidly using predictive tools and modeling. By creating isotherms for each ingredient and doing mixed modeling, we can measure moisture and water activity levels and create a new isotherm for the finished product.


Hygroscopicity is how quickly a product absorbs moisture from the surrounding atmosphere. It is a critical factor in protecting powders' quality and stability. Hygroscopicity is a function of temperature and humidity, and sorption isotherms can determine the relationship between those factors. This is particularly important in excipient selection, as it can ensure that the excipient has the necessary qualities to protect the product. 


Generally speaking, water activity increases as temperature increases. With this in mind, it's essential to have a range of isotherms for powders so you can assess and predict how the critical water activity might change as the product leaves the facility and is affected by outside conditions. With different isotherms at different temperatures, we can predict the water activity at nearly any temperature.

Figure 2. Isotherms model the relationship between moisture content and water activity at a set temperature.

Assessing structure

The relationship between water activity and moisture content is visualized in an isotherm. Because that relationship is based on the product's structure, we can assess the structure of the product using isotherms. For example, by using isotherms, we can model and predict the degree of transition between crystalline and amorphous powders and hydrate formation.

Crystalline vs. Amorphous

Figure 3. Isotherms show important relationships and distinctions between crystalline and amorphous structures and materials.

In short, with the help of DDIs, analyzing and predicting food product stability can be a direct and straightforward process.

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