At one end of the spectrum of the moisture world is the classic Speedy Moisture Tester where you use the reaction of water with calcium carbide to cause a mini explosion resulting in a moisture measurement reading. This method is used frequently for soils, concrete, and other like materials.
Many accessing our web site ask questions such as:
“How does water content affect water activity?”
"How is water activity different from water content?”
”Can I convert from moisture to water activity?”
I previously commented on water activity and now hope to clarify the differences between water activity and moisture content. Given that both of these measurements deal with water connected to a material, we must first understand of water content in a product.
Loss-On-Drying moisture analysis seemed like a simple process until, in a state of naïve bliss, I promised to look at evaporation, vapor pressure and bound water. While I was otherwise occupied with hese realities, I offered to enter the world of witchcraft and folklore; water activity.
Water activity is the water in a material available to support the growth of microorganisms. Consequently, the measurement of water activity is important in areas such as food processing, pharmaceutical production, products affected by mold, and a host of products that change characteristics when exposed to moisture.Read More
Last week, as I was reflecting on a recent moisture content problem, I recalled our series “Loss-on Drying and Other Moisture Mysteries.” In that series I examined moisture chemistry in products. However, I did little to define moisture content.
The answer to the question, “How Long Does a Water Activity Test Take?” is, as with most testing questions, “it depends.” Some water activity meters promise a test completed in a very short time; some in as little as five minutes. This time is an arbitrary selection that may or may not produce a satisfactory result.Read More
The other day, I woke up with a lingering quandary: Are the concepts of
Moisture Content and Water Activity the same thing?
As usual, I’ve decided to take on the task of clarifying the difference. I hope I pull it off.
From the perspective of someone who supplies instruments that measure moisture content, water activity has not been a primary consideration. However, I believe that comparison and contrast of these important concepts will be useful.