A system for detecting a change in material composition in a product including a microwave transmitter emitting a microwave signal at a predetermined microwave frequency composition, and an ultrasonic transmitter emitting an ultrasound signal at a predetermined ultrasound frequency composition into at least a part of the product to create a density displacement within the product. The system further includes a receiver to receive a microwave signal and/or an ultrasonic signal passed through at least apart of the product, device to measure the attenuation and/or runtime between each emitted signal and each received signal, respectively, under the influence of the created density displacement, and a comparator to compare the measured attenuation and/or runtime with a previously determined attenuation and/or runtime to determine a change in material composition to detect a possible change in material composition in a product.