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Don’t squeeze the fruit - new sensor tests ripeness

The days of squeezing fruit and checking sell-by dates on meat products may soon be over, thanks to a revolutionary new metal-oxide sensor being developed by a team of German scientists.

The micro-sensors, which resemble tiny golden spiders, instantaneously detect changes in food ripeness or the first signs of decay and transmit the data online to food wholesalers. That way, a warehouse foreman knows when fruit is just about ripe and ready for shipment to the supermarket.

The system has been developed by researchers at the Fraunhofer Institutes for Molecular Biology and Applied Ecology IME in Schmallenberg and for Physical Measurement Techniques IPM in Freiburg, both cities in Germany.

“We have brought together various technologies based on the use of metal oxide sensors, similar to those installed in cars, for example, to close ventilation vents when driving through a tunnel. Researchers at IPM have developed these sensors further,” explains Dr Mark Buecking, department head at IME.

“If a gas flows over the sensor at temperatures of 300 to 400 degrees Celsius, it will burn at the point of contact. The subsequent exchange of electrons changes the electrical conductivity,” says Buecking.

“Before the gas reaches these sensors, it has to go through a separation column with polymers. Certain substances are already filtered out here,” he adds.

A prototype of the analysis equipment already exists. Initial tests were promising, with the German researchers saying the system measures the volatile substances just as accurately as conventional equipment used in food laboratories.

In a further step, the German researchers want to optimize the system and adapt it to specific problems.

Buecking reckons that the equipment could come onto the market at a four-digit euro price, making it affordable to large-scale food wholesalers and supermarket chains.