Micro-CT of an Avocado
Avocados, once a rare treat available only in west coast cities able to sell fresh fruit in season, are now found year round across the country. Loosened import restrictions have led to the increase in availability, as Mexico is the world’s largest producer of avocados. Although most avocado varieties are delicate, ripening too quickly to ship and with thin skin that bruises easily, improved production methods have resulted in the Haas avocado—a slow-ripening variety with a longer shelf life and a thick skin.
According to the US Department of Agriculture, avocado prices have risen from $0.98 in April 2016 to $1.27 in April 2017. Prices are expected to continue to rise due to a growers’ strike in Mexico, which supplies 82% of avocado shipments to the United States.1 With the increased demand and expedited shipping, quality can be an issue. As a test, we wanted to see if bruising or air gaps were visible in an avocado that was shipped to us in poor shape. Using the SkyScan 1173, we were able to scan the avocado and see the degrading regions (Figure 2).
Micro-CT Scan of the Avocado
The micro-CT scanning of our avocado reveals clear regions of degradation. When looking at the 2D axial slice image, you can see the black regions, which show air pockets. These pockets form by bruising and oxidation of the fruit. Similar to an apple, when the internal fruit is exposed to oxygen, the polyphenol oxidase enzyme in the avocado begins the compound conversion. These phenolic compounds turn into quinones that contribute to the brown coloring. Over time, the cell structure completely breaks down, forming air voids (Figure 2 above).
There are some ways to keep your avocadoes fresh once you have cut into them. One method is to chill the avocado in the fridge, which slows the enzyme activity. Another option is to rub the cut portion of the avocado with lemon juice. The acid from the lemon juice slows the enzyme reaction and prevents the avocado from browning so quickly. A third way is to the leave the pit in the avocado when the avocado is cut, which will shield the avocado fruit near the pit from browning, although the exposed fruit will still brown.2
This demonstrates just one of many applications where identifications of quality can be made with micro-CT imaging. We hope you found this image of the month interesting. If you have an image of the month sample that you would like us to scan, please let us know by calling Brandon Walters at 610-366-7103 or e-mailing firstname.lastname@example.org.
BOTH SCAN SPECIFICATIONS
NRecon, DataViewer, CTVox
Micro Photonics Imaging Laboratory, Allentown, PA