Food gas sensor could show when fruit is ripe and meat fresh

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By Rory Harrington, 05-Aug-2009

A new sensor that analyses gases given off by foods could be used to check their safety, quality and reliability quickly and economically, said the German research team behind the device.

Food suppliers could accurately gauge the ripeness of fruit stored in a warehouse to know when best to deliver it to a supermarket or whether fish or meat is still fresh, team member Dr Mark Buecking told

Volatile components

Developed by researchers at the Fraunhofer Institutes for Molecular Biology and Applied Ecology IME and the Physical Measurement Techniques IPM in Freiburg, the novel system uses volatile components to check for characteristics such as ripeness or freshness.

Using either a hand-held or fixed device, a sensor with a surface heated to high temperatures analyses the gas emitted by food before displaying colour-coded results on a screen; green for optimum level of ripeness or freshness; yellow to indicate it is not quite ready, and red to show either the produce needs more time to mature or has spoiled in the case of meat or fish.

Metal oxide sensors

"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,” said Buecking.

“Researchers at IPM have developed these sensors further. If a gas flows over the sensor, at temperatures of 300 to 400°C, it will burn at the point of contact. The subsequent exchange of electrons changes the electrical conductivity.”

It is this change that allows the instrument to evaluate the gases and come up with a reading.

Black box

Buecking explained that before the gas reaches these sensors, it has to go through a separation column with polymers that filters out substances and allows them to analysed individually or disregarded if they play no part in the process. The analytical software, contained in a so-called black box, can be changed or recalibrated according to the food being checked.

The group has already developed a prototype and the system is currently being tested in the German pork sector. The project aims to develop an on-line device used on the slaughter line that is able to detect an unpleasant off-flavour in male pigs, known as boar taint – which can arise as a result of the production of sexual hormones.

Buecking explained: “It's true that most pigs are slaughtered well before sexual maturity – before any odorous substances have formed. As there is the risk, however, that some boars could produce odorous substances prematurely, all boars are castrated when they are young piglets. Castration may not be necessary in the future if the pork could be tested on-line before it is packaged.”

He said the group was in general interested in teaming up with appropriate companies to discuss manufacturing the system on a commercial basis and hoped to bring the system to market within two years.

Supply chain benefits

The benefits of the system to those involved in the supply chain could be numerous and important, said Buecking.

“The robust and easy-to-handle system is fast and facilitates detection in minutes instead of hours or days,” he said. “It can be implemented into the process itself as well as into a quality management system via a network to record and store data on a digital basis. We also believe it is economical compared to laboratory tests, which are slower and costlier.”


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