MIT scientists have unveiled a device which can determine the ripeness of an apple using ultraviolet light to analyze the glow of chlorophyll in the fruit’s skin. Anshuman Das, a postdoctoral researcher in MIT’s Media Lab, is the lead author of a paper describing the development of the device. Using off the shelf components, Das and his team created a spectrometer that makes the chlorophyll in the apple’s skin glow depending on its level of ripeness. Since chlorophyll breaks down over time, the dimmer the glow, the riper the apple is. The device uses Bluetooth to send the data to an Android app in order to compare it to a database of the results from apples at various stages of ripeness. The user can use this to determine how long the apple has been ripening from a baseline amount.

The team developed the device using almost entirely commercially available parts, other than the chip that picks up the fluorescence of the apple, which had to be specially ordered. This kept the cost of the device relatively low. Even the computing power of the device comes from a small do-it-yourself kit, using the open source coding language Arduino. Including the smartphone, the kit can be assembled for less than 250 dollars.

The device could provide apple distributors with the ability to better determine where and when to send their products. Coordination is required to make sure apples are available in stores year round, since they only grow during certain seasons. One way to do this is to make sure the ripest apples are shipped to places where they will sell quickly, but this can require some guesswork on the part of distributors. According to the developers of the new device, this can lead to significant waste. Spectrometers which currently exist also offer the ability to measure the brightness of light at different wavelengths, but these devices are large, expensive, and impractical for most apple farmers and distributors.

Das notes a future for the device measuring the ripeness of other fruits and vegetables besides apples, some of which contain even more chlorophyll than apples, which could make the device even more effective. The device holds the potential to significantly reduce wasted food.

The study was published on September 8th in the journal Scientific Reports.

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