Want an apple with a perfectly crisp, sweet, juicy bite? A new handheld device can help. Researchers have made a portable spectrometer that scans fruit and wirelessly relays data to a smartphone app that tells you whether the fruit is ripe.
Unlike the bulky, expensive spectrometers used today to test food and drug quality, the new gadget is about the size and weight of a collectible matchbox car. It consumes little power, and it costs less then $250 according to its inventors at MIT.
Farmers could use the smartphone-based device in the field to determine the ideal harvesting time for apples and other fruit, the inventors say. Or it could find use in storage facilities to sort fruit and vegetables and to check ripeness. It could also be adapted for consumers, helping them avoid the unpleasantness of tart or rotten fruit.
The food industry today uses one of two methods to test apple ripeness. One is to measure firmness using penetrometers and sclerometers. Both devices rely on measuring the force required to insert a probe into the fruit. The other test in use today, called Brix, measures the sugar content of the fruit juice using light refraction. Both methods are destructive, says MIT Media Lab researcher Anshuman Das.
Das and his colleagues turned to optical spectroscopy instead. “We use light to probe the sample, making the technique rapid and non-destructive,” he says.
The team bought a spectrometer chip and packaged it along with an ultraviolet LED, optical filters, a Bluetooth module for wireless data communication, an Arduino microcontroller for analog-to-digital conversion, and a rechargeable lithium-ion battery into a small 3D printed case.