Scientists at the University of Leeds in the UK have shown that massive bursts of ultrasound are generated during the first second of biting into crunchy food, which are then simultaneously analysed by the ears and mouth.
The discovery of recordable ultrasound pulses could be of great interest to the food manufacturers, who in the pursuit of the perfect crispy/crunchy texture for their products, employ an army of trained tasting panels.
These people form the crux of manufacturers efforts at product consistency and quality control in terms of creating the optimum texture for a product.
"Food is, in effect, talking to us and we innately understand what its saying about texture by interpreting the sensations through our ears and mouths," said food physicist Professor Malcolm Povey.
"Our research shows that the sound and feel of food in the mouth is as important as taste, look and smell in deciding whether we like something or not."
Using a microphone, an acoustic microscope, some simple software and an enviable supply of different biscuits, Povey proved that the energy produced by the very first crack of a biscuit breaking is released as distinct pulses of ultrasound sound waves beyond the range of human hearing.
Slowed down and plotted onto a graph, the pulses can be seen as a series of tall peaks, but actually last only for milliseconds and are generated at frequency levels more usually associated with bats, whales and dolphins for echolocation.
"It's a good job we cant hear all the energy in these pulses as they would damage our ears if we did," said Povey. "They're enormously loud bangs often way beyond safe decibel levels."
He said that the technique of recording the sound of biting or breaking crispy food and simply counting the peaks of soundwaves could provide a cheap, quantifiable and accurate analysis of texture, that will ensure absolute product consistency. "The more peaks, the crispier it is its as simple as that," he said.
The research also demonstrates that the human mouth is extremely accurate in its innate analysis of these ultrasound pulses. Test results show a very high correlation to the machine-measured results by both professional tasters working in the food industry and untrained volunteers.
"We're not trying to replace tasting panels," said Povey. "But a machine-measured test is a quick and simple way to check consistency of products once the desired texture for a product has been decided. However, the research does suggest that the training of food tasters in respect of measuring crispness is probably unnecessary."