Hydrogels with a taste are administered into the mouth via a small tube
Shulin Chen
An electronic tongue that can replicate flavours like cake and fish soup could help recreate food in virtual reality, but can’t yet simulate other things that influence taste, such as smell.
Yizhen Jia at The Ohio State University and his colleagues have developed a system, called e-Taste, that can sample a food and work out how to partly recreate its flavour in someone’s mouth.
This involves using chemicals that correspond to the five basic tastes: sodium chloride for salty, citric acid for sour, glucose for sweet, magnesium chloride for bitter and glutamate for umami. “Those five flavours are already accounting for a very large spectrum of the food we have daily,” says Jia.
The system uses sensors to detect the levels of these chemicals in food, converts them to digital readings, and then sends these values to the pump, which pushes small amounts of different flavour-containing hydrogels into a small tube under a person’s tongue.
First, the researchers tested the system for single flavours, asking 10 people how well the device reproduced sourness on a five-point scale, compared with real samples of sour tastes. They gave the same number for the reproduced and real sourness 70 per cent of the time.
The team then tested whether the system could replicate more complex tastes — lemonade, cake, fried egg, fish soup and coffee — and asked a group of six people whether they could distinguish between them, finding that they could more than 80 per cent of the time.
However, focusing only on flavours like this isn’t very useful, says Alan Chalmers at the University of Warwick, UK, because other senses are also involved in how we taste. “Next time you have a strawberry, close your nose and eyes. A strawberry is very sour, but it is perceived as sweet because of its aroma and the red colour. So if you send just sour across with their device, you will never know that it is actually from a strawberry.”
“An e-tongue such as this is able to extract the amount of sweetness [and] sourness, but not taste as a human tongue perceives them,” he says.
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