Listening to what the tongue feels

Creaminess or astringency of new foods can be determined by measuring the sound generated by the food interacting with the tongue during consumption. This new technology, developed by NIZO food research, records and analyses the sound of rubbing of the tongue against the food and can be used to predict the sensory effects of food innovations.

When formulating for low fat or low carb products, developers have to deal with a significant change in mouthfeel and need to compensate for these changes. Until now, standard rheology measurements are used to determine viscosity. More relevant is the way a product changes friction of surfaces and for this reason tribology is often attempted. However, the plastic or stainless steel surfaces used in tribometers cannot sufficiently mimic the soft, mucous-coated papillary surface of a live tongue.

A new technology, developed at NIZO, called ‘acoustic tribology’, records and analyses the sound generated by rubbing or tapping of the tongue in the mouth during mastication. The inventor, George van Aken, explains that the sound produced by rubbing or tapping is caused by the same vibrations of the tissue that are sensed by the mechanoreceptors in the tongue that signal the sensation of roughness, stickiness, structural coarseness of any food (fluid, semisolid and solid). Acoustic tribology is non-invasive, measures in real time and can be applied directly on human subjects without any preconditioning or preparation of the body surfaces.

In a recent publication in Food Hydrocolloids, the technology is demonstrated for sensations felt by the tongue in relation to astringency and creaminess for a range of dairy systems with varying fat content such as milk, yoghurt, quark and cheese.

“The advantage of acoustic tribology,” van Aken confirms, “is that we measure where the consumer experiences the food: in the mouth. It gives objective information about the suppleness of movements and thus the lubricating behaviour of the food on the tongue.” This technology can be applied to a wide range of foodstuffs.