Moisture content in honey determination with a shear ultrasonic reflectometer

An ultrasonic method, based on the measurement of the complex reflection coefficient at an interface (elastic material)/(viscoelastic material) has been developed for shear waves and an operating frequency of 10 MHz. With this technique, the dynamic elastic moduli G' and G '' can be obtained with a high accuracy. For various honeys and moisture contents we show that the temperature for which (G ''/G') = 1 undergoes an important variation (25-3 degrees C) for moisture contents ranging from 15% to 20%. With this technique one can distinguish two honeys with moisture contents difference less than 0.2%. Regarding the high sensitivity of the method, considering the fact that ultrasonic waves can propagate through optically opaque materials and is a nondestructive approach, we propose a discussion about the application of this technique for honey quality control. (C) 2009 Elsevier Ltd. All rights reserved.