Moisture Impact on Powders
The physical properties of powders directly impact their processability. This probably isn’t a surprise to anyone, especially if you are previously aware of Particle Technology Labs and what we do for a living! Powder processing involves moving, compacting, packaging, milling, and agglomerating just as a few examples. Particle Technology Labs helps clients on a daily basis investigate powder processing issues as well as predict performance when handling powder products. Any plant manager and production engineer can tell you that moisture has a significant impact on all of the powder processing steps previously mentioned. As the spring season begins here in North America, specifically Chicago, and with summer not far behind…thoughts turn to warmer temperatures, sunny days, the potential to be closer than 6 feet from other individuals and more humid conditions.
Moisture and Cheese
So, you may be asking yourself, “Why is cheese in the title of this blog post? I thought this may be about photography and this guy is talking about powders instead.” Well, here at Particle Technology Labs, it is never a dull moment and we assist with a wide variety of sample types and client issues.
This blog entry is about how moisture can affect the flowability of powdered cheese! Not sure if you can get a more interesting nor tasty story than this! Particle Technology Labs is in a unique position to have the instrumentation to investigate this very topic. Several years ago, a client asked us to evaluate how elevated moisture levels during storage would affect their product. This would allow insight into what level of control would be required when manufacturing, packaging, shipping and processing their powdered cheese. The information would not only be valuable to them but also to their customers and ensure consumer satisfaction.
How we did it
There are several classic ways to evaluate powder flowability (angle of repose, shear cell testing, flow through an orifice, Carr Indices, etc.). While classic and commonly used in several industries, most are relatively rudimentary and/or can have low reproducibility due to operator skill level and how the powder is handled during the testing. A popular instrument now on the market for the last 15+ years has improved standardization of powder flowability measurements and provided a more comprehensive testing approach in a single platform. This instrument is the Freeman Technology FT4 Powder Rheometer. The FT4 measurement sequence first conditions the powder in a repeatable way to remove any “history” in the powder bed prior to testing. This conditioning step helps improve reproducibility and comparability between samples. Following the conditioning steps, a variety of attachments and testing schemes are utilized to measure the energy it takes to move a blade through the powder bed. Learn more about FT4.
Particle Technology Labs addressed this client’s moisture question by first placing portions of their cheese sample in our temperature and humidity-controlled oven. The sample was stored at a defined temperature and relative humidity level over the course of several days. The sample was then removed from the oven and tested at the prescribed time points on the FT4. Below is the outcome….
Basic Flowability Test
What does this tell us?
The graphs shown are just two of several test types the FT4 is capable of exploring. The first graph shows that as the cheese powder sat in the higher relative humidity environment longer, it actually required less energy for the powder to move. Why is this? One possibility is that as the powder adsorbed moisture, the moisture acted as a lubricant reducing the energy needed to generate flow. The second graph illustrates that as the cheese powder adsorbed more moisture it became easier to compress the powder. Why? Quite possibly for the same reason as before…. the higher moisture level acted as a lubricant or caused the solid powder particles to become more elastic or plastic-like and thus more compressible! Any process or packaging engineer should start to see the benefit of how this information could help in manufacturing control and/or development as well as packaging decisions.
How much moisture was adsorbed?
This specific question was not explored; however, Particle Technology Labs can assist with this question as well through the use of dynamic vapor sorption (DVS). In short, this analytical technique places a small quantity of powder on a microbalance and monitors the amount of mass gain as increasing or decreasing levels of moisture are applied to the sample. Yet another critical testing parameter used by the food industry related to moisture and how it may pertain to shelf life and/or microbial inhibition is a test called water activity. Water activity can be used to predict if a product will have an affinity to adsorb moisture or give off moisture to its environment. This can be used to help determine proper packaging requirements, if microbial growth will be encouraged, etc.
What if you don’t like cheese, why should you care about this story?
That is a very valid question, but I would tentatively ask….”Really? Who doesn’t like cheese????”. But if that is truly the case, it doesn’t take a lot of imagination to envision how these types of tests could help with numerous other food products (flavorings, protein powders, baking ingredients), pharmaceutical formulations (tablet production) as well as the construction material industries (concrete, drywall compound, etc.). The topic of moisture’s impact on powders and how they behave is as varied as the types of cheese! If you run into a powder processing problem, keep Particle Technology Labs in mind. We have the ability to assist with your unique problem and provide results to help answer critical processing questions and improve product performance. We offer a comprehensive array of techniques when it comes to powder characterization.
How Particle Technology Labs can help
Particle Technology Labs is a fully independent, cGMP compliant and ISO 17025:2017 accredited laboratory. Our lab has nearly 30 years of experience in the particle characterization field. As an independent laboratory, we offer a variety of instruments, manufactured by multiple vendors. Our experts can help evaluate if your sample is appropriate for a specific technique. If you have any questions about the suitability of your sample for powder flowability, dynamic vapor sorption or water activity, please do not hesitate to contact us. Particle Technology Labs provides consultations for testing inquiries free of charge and we are always happy to discuss your testing needs.
By William Kopesky, Director of Analytical Services