Get ready to taste laser-tested fruits

Researchers have developed a laser biospeckle method to help farmers harvest "climacteric" fruits like apples, bananas, pears and tomatoes at their precise peak in ripeness.

The ability to detect when to harvest "climacteric" fruits to ensure "peak edibleness" in terms of both taste and texture may soon be available, said the team from Saint Joseph University in Lebanon and the Universite de Bretagne Occidentale de Brest in France.

What's the significance of this "climacteric" peak?

Fruits are divided into two categories: climacteric or non-climacteric fruits.

"Climacteric fruits continue their maturation off the tree or vine so these fruits emit ethylene and are characterised by a climacteric peak - indicating a maximum ethylene release," said Rana Nassif, postdoctoral researcher affiliated with both Saint Joseph University and the Universite de Bretagne Occidentale de Brest.

This peak signals that the fruit has reached its maturity.

After this point, the fruit is more susceptible to fungal invasion or begins to degrade from cell death.

In the new technique, laser light interacts with any medium through different processes such as scattering, absorption and reflection.

Photons scattered by the medium interfere with the incident light field to create a speckle pattern.

By tapping biospeckle activity, generated by illuminating a biological medium with coherent light, the researchers studied the evolution of two batches of Golden apples' speckle patterns as they underwent the ripening process in both low- and room-temperature environments.

To do this, the team used a rather simple setup that involves coherent light, a laser beam polarizers and quarter-wave plates to generate different incident polarisations and a digital camera to record the speckle pattern.

"Simplicity and low cost are the key advantages of our technique," Nassif said.

The team's ultimate goals is to develop a portable tool to enable farmers to non-invasively assess their fruits' maturity in orchards or fields to detect the optimal time to harvest their crops.

"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," said Nassif.

The paper appeared in the journal Applied Optics.