Scientists at the Fraunhofer Institute in Dresden have developed a tiny infrared spectrometer that can measure the level of water, sugar or starch present in a piece of fruit.

The device is smaller than a sugar cube, and once made more compact, could eventually be installed in smart phones, allowing consumers to test market fruits on-the-go.

Reflected light

Infrared light waves emit from the device when a person points it at a piece of fruit. Heinrich Grüger, the Fraunhofer scientist who invented to spectrometer, says these infrared light waves are on the longer end of the spectrum and reflect not only from the surface of the object.

The light waves also penetrate millimeters or even centimeters into the object, reflecting back a spectrum of light that the device then measures.

"We don't just want to know whether the apple is red," Grüger told DW.

And since different substances reflect back the infrared light in different ways, this can tell what is within.

Software would compare the infrared reflections with data for the type of fruit in a database, giving the consumer special information.

Measurements could reveal the relative water content, or the amount of starch, and even differentiate between sugars, such as glucose, sucrose and fructose.

"In this way, we could judge whether the fruit has a reasonable amount of sugar, and therefore whether it's ripe," Grüger said.

Smaller than a sugar cube

Similar spectrometers already exist, but this new one is exceptionally small.

At about two-thirds the size of a sugar cube, it's about 350 smaller than other such devices.

The scientists at the Fraunhofer Institute for Photonic Microsystems manufactured the components directly onto silicon wafers, and have even devised a way for them to be mass produced.

Market applications for the tiny spectrometer, expected within three to five years, could include smart phone integration. But the scientists say that in order for that to happen, they will have to make it smaller still.

The device doesn't just have to be used for fruit - it could also be used to detect forgeries, or reveal whether a car has been repainted, and test the content of drugs and cosmetic creams.

Soon, a smart phone user could install a "fruit app" allowing him or her to scan fruit at the market. The only thing is, the user would have to make sure to select a comparison with the right type of fruit - otherwise the wrong information could come out.

The spectrometer is unable to tell the difference between a steak and pear - at least, for now. But there's probably another app for that anyway.

Author: Vera Freitag / Sonya Angelica Diehn
Editor: Zulfikar Abbany