Who hasn’t cringed after coming home from a grocery shop to find that those expensive avocados we thought were going to be ripe and tasty turn out to be duds? Despite learning to feel for that perfect amount of squish when squeezing for ripeness at the store, I still find myself having to toss too many avocados that aren’t fit for even mashing into guacamole. That’s why I am excited to see that research is taking place on several fronts to save us from those sad kitchen moments.
First comes news that researchers at Cranfield University in the U.K. have developed a test that “could guarantee the perfect avocado.” 1 That is a big promise! Here is how they explain the concept:
“Developed and tested by Cranfield University, the technology uses a laser and small vibration to test the individual fruits’ resonant frequency, giving a reliable assessment of ripeness without damaging the avocado… 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.” 1
A professor in the Environment and Agrifood program at Cranfield, Leon Terry, explained, “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 test we have developed could be extended to other fruits.” 1
You can view a short (very short!) video of the technology at work below: 2
If you looked at the mechanism in the video and wondered how on earth it could ever be practical, it turns out that avocados usually travel on conveyor belts at some point in their journey to suppliers and retailers. A research fellow with the Cranfield team said that they had tested the technology in a real factory line and found it promising. They envision “a simple ‘traffic light’ system [that] 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.” 1 That would certainly cut down on food waste in my own kitchen!
Meanwhile at Harvard engineering students have developed a device in partnership with a “predictive food safety startup” named Savormetrics, which measures certain chemical properties of an avocado to predict when the avocado will be ripe. So far, the prototype sensing device was found to be 60% accurate within one day of estimating optimal ripeness and another 30% of scans were accurate within two days. 3
The Harvard/Savormetrics team envision retailers being able to “set different prices for different levels of ripeness, or change store displays so the ripest avocados are at the front.” 3
Savormetrics already markets “FoodSafe Analyzers” they like to call “Zappers” with sensors that can analyze shelf life of produce or the taste profile of processed food. The Zappers unite artificial intelligence (AI) with the sensing system and, according to CEO Harjeet Bajaj, “can even pick up chemicals and predict chemical reactions that may lead to carcinogen formations at the parts per billion level.”4 Bajaj went on to say, “If you can predict an adverse situation related to food quality, you have a chance of preventing it from actually happening.” 4
It would be wonderful to imagine a time when the Zapper technology would be widely employed to prevent what seem to be a never-ending string of E.coli outbreaks traced back to some of our favorite produce like romaine lettuce.
See our article from last year, Why Are We Always Getting Sick from Freaking Lettuce?
As far as the avocado sensing device goes, Savormetrics is currently refining the prototype and plans to bring it to market, while offering the student engineers “a stock option opportunity.” 3
For readers wondering about a low-tech way to see if an avocado is ripe, a University of Florida’s Institute of Food and Agricultural Sciences blog offers this guidance: 5
- Gently squeeze the fruit in the palm of your hand.
- Ripe, ready-to-eat fruit will be firm but will yield to gentle pressure.
- Avoid ones with bruises, loose skin, or the ones where the stem end is showing decay.
- Avoid fruit with dark blemishes on the skin or over soft fruit.
The Cranfield team’s paper entitled Non-destructive discrimination of avocado fruit ripeness using laser Doppler vibrometry was published in Biosystems Engineering, linked below.6 The Harvard team’s project is described in a university press release here. 3
—R.A. Kroft
Sources
1Cranfield University. New Test Could Guarantee the Perfect Avocado. Press Release No. PR-SWEE-20-058. 5 May 2020.
2Video. Cranfield University. Lasers and vibrations assessing fruits’ ripeness. 13 May 2020.
3Zewe, Adam. Forestalling Food Waste: Student-developed Device Predicts When An Avocado Will Be Ripe. Harvard John A. Paulson School of Engineering and Applied Sciences. Press Release. 20 July 2020.
4Harris, Lois. Preventing Food Recalls Using Artificial Intelligence. Global Food Safety Resource Blog. 13 November 2019.
5Maddox, Martha. Avocado Selection, Storage and Preparation. University of Florida Institute of Food and Agricultural Sciences Blog. 12 May 2020.
6Landahl, Sandra and Terry, Leon A. Non-destructive discrimination of avocado fruit ripeness using laser Doppler vibrometry. Biosystems Engineering. 2020:194;251-260.
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R.A. Kroft writes about her day-to-day journey in living a smaller, more sustainable life and other topics that interest her.
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