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No More Guessing — Detecting the Quality of Fruits with Ultrasound

An ingenious way to know when the fruit is ready for harvest

We’d love to know precisely when the fruit is ripe, not a moment early nor too late. Photo by Amie Dawson from Unsplash.


Future of Agriculture

Think of the fruit you’re about to eat.

How do you know it’s ready and not green?

You might judge it by the color of the surface, but that doesn’t work with fruits like watermelon or avocado.

Okay, now you have to touch it, tap it, but you’re still not 100% certain that you’ll get it right.

Now think of increasing the scale of your decision.

Imagine trying to decide when to cut thousands of fruits at the right time so that you don’t end up with a bunch of useless products. Well, they might not be useless if you harvest them too early, but the delivery would be delayed, and that would hurt your pocket as a farmer or business owner.

On the other hand, if you harvest it late, that’ll mean less time on the supermarket shelf and more potential waste.

In some instances, it’s not just a matter of timely delivery. Fruit quality is also a key factor here.

Take the kiwi as an example.

If harvested prematurely, the outer and inner shells won’t grow synchronously, which in turn would make the ‘if it yields to slight pressure, it’s ripe’ technique useless.

As smart as humans are, we’re always trying to find ways to make our lives easier and this area has seen a recent breakthrough.

Thanks to Javier von Marées R., the innovation project manager at a Chilean technology transfer hub, APTA, I was able to dive into a new and fascinating solution to this issue.

Without further ado, here’s the future of agricultural tech.

The first issue with fruit harvest — they easily spoil

How many times have you had to throw away those apples you bought only three days ago?

Fruits are highly perishable and we have to be very careful how we handle them. A lot of it goes to waste due to poor handling and faulty storage practices. In fact, between 20% — 40% of fruits being harvested never reach the consumer.

At this pace, do you think the United Nations achieving the “Zero Hunger by 2030” initiative realizable?

And the ones that do reach us, can be easily dismissed by their appearance. If we deem them ugly, they’ll easily end up in the garbage even if they’re in excellent condition.

A sad truth.

But one problem at a time.

How do we harvest fruits today?

We mainly rely on fruit pickers and their keen eye. Photo by Mert Guller from Unsplash.

In most cases, fruits are harvested manually. It’s up to fruit pickers to decide which fruit to pick so it’s imperative to distinguish a mature fruit from a green one.

There are essentially two approaches at play: destructive and non-destructive.

The penetrometer is an example of the first one. It relies on measuring the firmness of the fruit’s flesh. By penetrating the fruit with this device, we’re able to measure the pressure of its surface layer.

Why is that helpful?

Because we can find the fruit’s ripeness and determine if it’s ready to be harvested. However, this technique damages the fruit significantly and it doesn’t get to the core, so a lot of it goes unmeasured.

Realistically speaking, workers cannot, and will not, perform this process on each fruit.

Not practical at all.

The second technique can cover much more ground and it doesn’t destroy the fruit. It relies on wave emissions to test the fruit’s maturity.

For instance, the near-infrared spectroscopy (NIRS) bounces radiation on and off the fruit and analyzes its reflection. Depending on the object’s chemical properties, you’ll get a distinctive spectrum of light emissions for each fruit.

After gathering the data, you compare that spectrum to a fruit quality model used to estimate the fruit’s maturity level.

So for instance, a green peach will have a different light profile from a ripe one. You’ll be able to see the differences in chlorophyll, firmness, and other parameters that will help you decide when to harvest it.

But there are certain setbacks

Both invasive and non-invasive methods have some limitations that require a new approach on how to assess the food’s maturity level.

Here’s what the inventors of this new tech point out:

  • The relationship between a wavelength and a specific quality attribute is not always clear in the non-destructive approach.
  • Non-destructive techniques don’t provide information on the different layers of a fruit. They just give an overall analysis.
  • Only a small portion of samples are analyzed as a representative sample, but fruits can show different levels of ripeness, even on the same plant!

We battle with food loss at different stages of the supply chain. Just in the US, 60% of land used to grow fruit is wasted. We would be much better using fewer acres in more efficiently. Even in countries with high levels of food insecurity, the food losses are astonishingly high, like in sub-Saharan Africa at 50% according to the FAO.

We are in great need to reduce food loss in the early stages of the supply chain and new technologies in fruit quality assessment can help improve our food production efficiency.

As you can see, we are in dire need of an alternative.

New tech to detect the fruit’s ripeness level

Sound waves might be the key to assess a fruit’s quality level. Photo by mtmmonline from Pixabay.


You must be thinking of pregnancy trimestral checkups. Or diagnostics. Or therapeutic applications.

Ultrasound is a sound wave that has a higher frequency than the one we’re able to hear, from 20khz up to several gigahertz. We can use it to find objects and see inside of them like having a sonogram of a fetus inside a womb.

The same principle applies to this new tech, but in this case, you’re looking at the different layers of a fruit. No need to deliver good or bad news to a mother on this one.

Jokes aside, this new promising technology comes from a group of Chilean researchers. Their patent application was submitted in 2019, and now it’s been approved for commercial use.

Think of an assembly line filled with fruits passing by.

Every fruit goes through a tunnel that has a device on top with two plunger-like transducers, each on one side (see figure below). One emits ultrasound waves (90 to 110kHz), and the other one captures those emissions back after it bounces off the fruit.

The device is always at a near range from a given fruit (not more than 3 cm away). According to the inventors, the device can assess the fruit’s ripeness at a rate of 1 fruit per second with a striking 93% level of certainty.

The software can differentiate the ultrasound signals emitted from each of the fruit’s layers so that it can determine its maturity levels.

If the fruit is ripe, it’s packaged for delivery. If it’s still too green, it’s sent to another area where it can be processed as a juice or jam.

Screenshot from the patent submission document, with the author’s permission.

In a nutshell…

At a first glance, when you talk about sound and fruit quality, there’s no immediate relationship between the two.

However, when you realize the deep flaws in the food industry system, particularly in the staggering amount of food loss and waste we pile up each year, there comes a time to go beyond the traditional approach to this issue.

And sound might be part of the solution we need, especially in increasing the efficiency of our food supply management.

We’re annually losing or wasting 1/3 of all the world’s food supplies. By increasing the way we manage food, we’d not only be able to reduce world hunger significantly but we’d be 10% closer to reduce all greenhouse gas emissions in the world.

Fresh fruits and vegetables are the most common products we dispose of. Up until now, we’ve had both destructive and non-destructive techniques to assess the fruit’s quality but these aren’t enough. They can mess up our efficiency in any of the stages between the fruit’s harvest and getting them to our dining room.

We need a better alternative, and the ultrasound detection system seems a promising technology:

  • Not only can it determine the ripeness of a fruit but it can also measure the maturity of each of its layers.
  • It’s a non-invasive technique which means that the fruit is undamaged in the assessment process.
  • It can detect 60 fruits per minute with an impressive 93% level of precision.
  • It’s able to classify fruits into different categories: packaging for supermarket delivery or aim it for juice or jam production.

As part of the new agricultural tech, ultrasound might be what we’ve been looking for to considerably reduce our worldwide food loss.

Food and sound, seemingly two poles apart. Who would have thought!

First, using music in treating wastewater to improve the bacteria’s degrading efficiency. Then, using sound to destroy harmful bacteria in meat products.

And now this.

A powerful thing sound is — wouldn’t you agree?

By Pavle Marinkovic on .

Are you curious about the world of sound and music? Learn how music can enhance a plant’s growth, the way sound changes our sense of taste, understand the music industry, and much more! Join my newsletter to embark on this journey of sound awareness.

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