'Traffic light' system for grading avocados

A technique for measuring the ripeness of avocados could reduce waste by up to 10% in the supply chain.

Developed and tested by Cranfield University in the UK, the technology uses a laser and small vibration to test the individual fruits’ resonant frequency, giving an assessment of ripeness without damaging the avocado. The researchers said the test could also be extended to other fruit.

Currently, avocado ripeness is tested either using a pneumatic device which pushes into the fruit or manual testing. This can result in up to 30% of the avocados wasted due to damage caused by testing during grading, with a further 5% loss at retail.

Cranfield University adapted a technology more often used in automotive factories to test the uniformity of large engineered parts. Laser Doppler vibrometry (LDV) beams a laser at the fruit to measure refracted light and uses small vibrations to test the resonant frequency. The vibrations are caused by a simple automated impact device that taps the fruit. The LDV test was proven to accurately predict the ready-to-eat stage of avocado fruit.

Professor Leon Terry, Director of Environment and Agrifood at Cranfield University, said: “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. Leaving the fruit undamaged is of great benefit and vastly reduces waste.”

The avocados travel on conveyor belts in single file, which means the LDV can test them individually. From there, an automatic sorting mechanism that largely exists already could be used to separate the ripe from unripe fruits.

Research Fellow Dr Sandra Landahl added: “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. 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 paper ‘Non-destructive discrimination of avocado fruit ripeness using laser Doppler vibrometry’ is published in Biosystems Engineering.

Image credit: ©stock.adobe.com/au/Mihail