Laser-powered vibration test reveals perfectly ripe avocados
As most fans of the leathery fruit can attest, telling when an avocado is of perfect ripeness can be a guessing game, but a new testing technique could eliminate the margin for error. The tool relies on lasers and vibrations to measure the firmness of individual fruit, without the prodding and prying that can cause damage and leave many destined for the waste bin.
The new testing technology was developed by scientists at Cranfield University, who say up to 30 percent of avocados currently go to the waste in the UK due to damage incurred during grading, followed by another 5 percent at retail. And with the UK importing nearly 10,000 tonnes of the fruit each year, there is a lot to be gained through improved grading methods.
In pursuit of this objective, the team turned to a technology known as laser Doppler vibrometry (LDV). By using an automated device to very gently tap the fruit and using lasers to map the tiny vibrations that result, this LDV test was able to reveal the resonant frequency of the individual fruits, and in turn the physical characteristics of their insides.
“Hard fruits create a higher frequency than soft fruits, so we calculated the perfect frequency for a ripe avocado and accurately measured this with the LDV test,” says Professor Leon Terry, Director of Environment and Agrifood at Cranfield University. “Leaving the fruit undamaged is of great benefit and vastly reduces waste. The test we have developed could be extended to other fruits.”
The team hopes this new grading technique can offer an alternative to the currently used pneumatic devices that push into the fruit, or simple manual testing by hand. In packing facilities, avocados travel down a conveyor belt in a single line, so the team envisages this LDV test could easily be used to test individual fruits as part of this process, and an automated device then sorting them depending on their levels of ripeness.
“We tested the accuracy of LDV on a real factory line, under lab conditions, and the method has real potential, giving accurate measures of ripeness without damaging fruit,” says research fellow Dr Sandra Landahl. “If developed, a simple ‘traffic light’ system could sort the fruit into those that are ripe, for discard or for storage, helping industry tackle food waste at this point in the supply chain.”
The research was published in the journal Biosystems Engineering.
Source: Cranfield University
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