Is it Ripe Yet? A Laser Can Tell

Wouldn't it be nice if you didn't have to inspect each and every apple, plum, or pear for ripeness at the grocery store? Standing at a fruit stand assessing potential purchases is not only time consuming, but relatively inaccurate. Now researchers have introduced a device that helps fruit suppliers measure ripeness, allowing for their fruits to hit shelves and stands at the perfect time.

"Fruits are divided into two categories: climacteric or nonclimacteric fruits," Rana Nassif, a researcher affiliated with both Saint Joseph University and the Université de Bretagne Occidentale de Brest, explained in a statement. "Climacteric fruits continue their maturation off the tree or vine... and are characterized by a climatic peak."

This "peak" indicates maximum ripeness for a climactertic fruit, but also means that it is now more susceptible to fungal invasion, and will start suffering from cell death. Therefore, timing is everything when selling these fruits.

A low cost technique to tell exactly when a fruit will be most ripe could only help suppliers and consumers alike. And that's where the laser comes in.

According to the journal Applied Optics, Nassif and her colleagues designed a device that measures ripeness by assessing something called a "speckle pattern."

"A group of sparkling and dark grains called 'speckle grains' make up this pattern. If the medium is biological - meaning that it presents some sort of cell activity - its speckle pattern will show changes with time," she explained. "And this pattern depends on the medium's scattering properties, as well as its own nature." (Scroll to read on...)

To showcase how their device works, the team fired laser light at a golden delicious apple - a type notoriously difficult for measuring ripeness, as its coloration barely changes as it matures.

The light scatters when it hits the apple, and the pattern of this photon scattering is what tells researchers their speckle pattern. A different pattern will develop depending on the ripeness of the fruit.

Most notably, they noted an increase in cell activity all the way up until the day of peak ripeness, and then a sudden fall-off. That should make predicting windows of time for average ripeness relatively simple. The team ultimately plans to make their device more accurate and portable.

"This is of great interest to fruit farmers - especially since most tests used today are either destructive or based on visual criteria that are often wrong," Nassif noted.

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