The new AquaLab TDL is an instrument that uses tunable diode laser (TDL) technology to accurately measure water activity in previously impossible to analyze samples. Water activity of food products is frequently measured to determine susceptibility to mold and microbial spoilage, to predict reactions that end shelf life, and to set and monitor quality in products affected by moisture. Other industries that rely on this measurement include pet foods, pharmaceuticals, tobacco, petroleum, lubricants, and plastics.

“One novel application of this new technology is testing the water activity of the oil inside large electrical transformers,” said Dr. Colin Campbell, Decagon Devices vice president of research and development. “Transformers which contain oil where water activity is too high can explode, causing power loss across the grid. TDL (tunable diode laser) technology will help eliminate this problem.”

The AquaLab TDL water activity meter measures water activity using a tunable diode laser, which locks onto a single absorption wavelength of water and reads only that band. Because it is specific to water and negligibly absorbed by molecules of other gases, the sensor is not affected by volatiles, which interfere with typical water activity sensors (dewpoint, capacitance). These standard sensors are affected by volatiles such as propylene glycol (a common dog food additive), alcohols, spices, and flavorings, and the resulting errors are not small.  For example, we know that adding alcohol to a sample decreases its water activity, but until now, sensors consistently showed an increase in water activity when alcohol was added. Thus, it has not been possible to know the water activity of such samples.  

TDL technology allows products containing certain spices, flavorings, alcohols, and other volatile compounds to be accurately tested for water activity for the first time.

Decagon Devices Inc., Pullman, WA 800-755-2751 www.decagon.com

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